mm: swap: swap cluster switch to double link list

Patch series "mm: swap: mTHP swap allocator base on swap cluster order", v5. This is the short term solutions "swap cluster order" listed in my "Swap Abstraction" discussion slice 8 in the recent LSF/MM conference. When commit 845982eb "mm: swap: allow storage of all mTHP orders" is introduced, it only allocates the mTHP swap entries from the new empty cluster list. It has a fragmentation issue reported by Barry. https://lore.kernel.org/all/CAGsJ_4zAcJkuW016Cfi6wicRr8N9X+GJJhgMQdSMp+Ah+NSgNQ@mail.gmail.com/ The reason is that all the empty clusters have been exhausted while there are plenty of free swap entries in the cluster that are not 100% free. Remember the swap allocation order in the cluster. Keep track of the per order non full cluster list for later allocation. This series gives the swap SSD allocation a new separate code path from the HDD allocation. The new allocator use cluster list only and do not global scan swap_map[] without lock any more. This streamline the swap allocation for SSD. The code matches the execution flow much better. User impact: For users that allocate and free mix order mTHP swapping, It greatly improves the success rate of the mTHP swap allocation after the initial phase. It also performs faster when the swapfile is close to full, because the allocator can get the non full cluster from a list rather than scanning a lot of swap_map entries. With Barry's mthp test program V2: Without: $ ./thp_swap_allocator_test -a Iteration 1: swpout inc: 32, swpout fallback inc: 192, Fallback percentage: 85.71% Iteration 2: swpout inc: 0, swpout fallback inc: 231, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 227, Fallback percentage: 100.00% ... Iteration 98: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 215, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% $ ./thp_swap_allocator_test -a -s Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% $ ./thp_swap_allocator_test -s Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% $ ./thp_swap_allocator_test Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% With: # with all 0.00% filter out $ ./thp_swap_allocator_test -a | grep -v "0.00%" $ # all result are 0.00% $ ./thp_swap_allocator_test -a -s | grep -v "0.00%" ./thp_swap_allocator_test -a -s | grep -v "0.00%" Iteration 14: swpout inc: 223, swpout fallback inc: 3, Fallback percentage: 1.33% Iteration 19: swpout inc: 219, swpout fallback inc: 7, Fallback percentage: 3.10% Iteration 28: swpout inc: 225, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 29: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 34: swpout inc: 220, swpout fallback inc: 8, Fallback percentage: 3.51% Iteration 35: swpout inc: 222, swpout fallback inc: 11, Fallback percentage: 4.72% Iteration 38: swpout inc: 217, swpout fallback inc: 4, Fallback percentage: 1.81% Iteration 40: swpout inc: 222, swpout fallback inc: 6, Fallback percentage: 2.63% Iteration 42: swpout inc: 221, swpout fallback inc: 2, Fallback percentage: 0.90% Iteration 43: swpout inc: 215, swpout fallback inc: 7, Fallback percentage: 3.15% Iteration 47: swpout inc: 226, swpout fallback inc: 2, Fallback percentage: 0.88% Iteration 49: swpout inc: 217, swpout fallback inc: 1, Fallback percentage: 0.46% Iteration 52: swpout inc: 221, swpout fallback inc: 8, Fallback percentage: 3.49% Iteration 56: swpout inc: 224, swpout fallback inc: 4, Fallback percentage: 1.75% Iteration 58: swpout inc: 214, swpout fallback inc: 5, Fallback percentage: 2.28% Iteration 62: swpout inc: 220, swpout fallback inc: 3, Fallback percentage: 1.35% Iteration 64: swpout inc: 224, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 67: swpout inc: 221, swpout fallback inc: 1, Fallback percentage: 0.45% Iteration 75: swpout inc: 220, swpout fallback inc: 9, Fallback percentage: 3.93% Iteration 82: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 86: swpout inc: 211, swpout fallback inc: 12, Fallback percentage: 5.38% Iteration 89: swpout inc: 226, swpout fallback inc: 2, Fallback percentage: 0.88% Iteration 93: swpout inc: 220, swpout fallback inc: 1, Fallback percentage: 0.45% Iteration 94: swpout inc: 224, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 96: swpout inc: 221, swpout fallback inc: 6, Fallback percentage: 2.64% Iteration 98: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 99: swpout inc: 227, swpout fallback inc: 3, Fallback percentage: 1.30% $ ./thp_swap_allocator_test ./thp_swap_allocator_test Iteration 1: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 131, swpout fallback inc: 101, Fallback percentage: 43.53% Iteration 3: swpout inc: 71, swpout fallback inc: 155, Fallback percentage: 68.58% Iteration 4: swpout inc: 55, swpout fallback inc: 168, Fallback percentage: 75.34% Iteration 5: swpout inc: 35, swpout fallback inc: 191, Fallback percentage: 84.51% Iteration 6: swpout inc: 25, swpout fallback inc: 199, Fallback percentage: 88.84% Iteration 7: swpout inc: 23, swpout fallback inc: 205, Fallback percentage: 89.91% Iteration 8: swpout inc: 9, swpout fallback inc: 219, Fallback percentage: 96.05% Iteration 9: swpout inc: 13, swpout fallback inc: 213, Fallback percentage: 94.25% Iteration 10: swpout inc: 12, swpout fallback inc: 216, Fallback percentage: 94.74% Iteration 11: swpout inc: 16, swpout fallback inc: 213, Fallback percentage: 93.01% Iteration 12: swpout inc: 10, swpout fallback inc: 210, Fallback percentage: 95.45% Iteration 13: swpout inc: 16, swpout fallback inc: 212, Fallback percentage: 92.98% Iteration 14: swpout inc: 12, swpout fallback inc: 212, Fallback percentage: 94.64% Iteration 15: swpout inc: 15, swpout fallback inc: 211, Fallback percentage: 93.36% Iteration 16: swpout inc: 15, swpout fallback inc: 200, Fallback percentage: 93.02% Iteration 17: swpout inc: 9, swpout fallback inc: 220, Fallback percentage: 96.07% $ ./thp_swap_allocator_test -s ./thp_swap_allocator_test -s Iteration 1: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 97, swpout fallback inc: 135, Fallback percentage: 58.19% Iteration 3: swpout inc: 42, swpout fallback inc: 192, Fallback percentage: 82.05% Iteration 4: swpout inc: 19, swpout fallback inc: 214, Fallback percentage: 91.85% Iteration 5: swpout inc: 12, swpout fallback inc: 213, Fallback percentage: 94.67% Iteration 6: swpout inc: 11, swpout fallback inc: 217, Fallback percentage: 95.18% Iteration 7: swpout inc: 9, swpout fallback inc: 214, Fallback percentage: 95.96% Iteration 8: swpout inc: 8, swpout fallback inc: 213, Fallback percentage: 96.38% Iteration 9: swpout inc: 2, swpout fallback inc: 223, Fallback percentage: 99.11% Iteration 10: swpout inc: 2, swpout fallback inc: 228, Fallback percentage: 99.13% Iteration 11: swpout inc: 4, swpout fallback inc: 214, Fallback percentage: 98.17% Iteration 12: swpout inc: 5, swpout fallback inc: 226, Fallback percentage: 97.84% Iteration 13: swpout inc: 3, swpout fallback inc: 212, Fallback percentage: 98.60% Iteration 14: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% Iteration 15: swpout inc: 3, swpout fallback inc: 222, Fallback percentage: 98.67% Iteration 16: swpout inc: 4, swpout fallback inc: 223, Fallback percentage: 98.24% ========= Kernel compile under tmpfs with cgroup memory.max = 470M. 12 core 24 hyperthreading, 32 jobs. 10 Run each group SSD swap 10 runs average, 20G swap partition: With: user 2929.064 system 1479.381 : 1376.89 1398.22 1444.64 1477.39 1479.04 1497.27 1504.47 1531.4 1532.92 1551.57 real 1441.324 Without: user 2910.872 system 1482.732 : 1440.01 1451.4 1462.01 1467.47 1467.51 1469.3 1470.19 1496.32 1544.1 1559.01 real 1580.822 Two zram swap: zram0 3.0G zram1 20G. The idea is forcing the zram0 almost full then overflow to zram1: With: user 4320.301 system 4272.403 : 4236.24 4262.81 4264.75 4269.13 4269.44 4273.06 4279.85 4285.98 4289.64 4293.13 real 431.759 Without user 4301.393 system 4387.672 : 4374.47 4378.3 4380.95 4382.84 4383.06 4388.05 4389.76 4397.16 4398.23 4403.9 real 433.979 ------ more test result from Kaiui ---------- Test with build linux kernel using a 4G ZRAM, 1G memory.max limit on top of shmem: System info: 32 Core AMD Zen2, 64G total memory. Test 3 times using only 4K pages: ================================= With: ----- 1838.74user 2411.21system 2:37.86elapsed 2692%CPU (0avgtext+0avgdata 847060maxresident)k 1839.86user 2465.77system 2:39.35elapsed 2701%CPU (0avgtext+0avgdata 847060maxresident)k 1840.26user 2454.68system 2:39.43elapsed 2693%CPU (0avgtext+0avgdata 847060maxresident)k Summary (~4.6% improment of system time): User: 1839.62 System: 2443.89: 2465.77 2454.68 2411.21 Real: 158.88 Without: -------- 1837.99user 2575.95system 2:43.09elapsed 2706%CPU (0avgtext+0avgdata 846520maxresident)k 1838.32user 2555.15system 2:42.52elapsed 2709%CPU (0avgtext+0avgdata 846520maxresident)k 1843.02user 2561.55system 2:43.35elapsed 2702%CPU (0avgtext+0avgdata 846520maxresident)k Summary: User: 1839.78 System: 2564.22: 2575.95 2555.15 2561.55 Real: 162.99 Test 5 times using enabled all mTHP pages: ========================================== With: ----- 1796.44user 2937.33system 2:59.09elapsed 2643%CPU (0avgtext+0avgdata 846936maxresident)k 1802.55user 3002.32system 2:54.68elapsed 2750%CPU (0avgtext+0avgdata 847072maxresident)k 1806.59user 2986.53system 2:55.17elapsed 2736%CPU (0avgtext+0avgdata 847092maxresident)k 1803.27user 2982.40system 2:54.49elapsed 2742%CPU (0avgtext+0avgdata 846796maxresident)k 1807.43user 3036.08system 2:56.06elapsed 2751%CPU (0avgtext+0avgdata 846488maxresident)k Summary (~8.4% improvement of system time): User: 1803.25 System: 2988.93: 2937.33 3002.32 2986.53 2982.40 3036.08 Real: 175.90 mTHP swapout status: /sys/kernel/mm/transparent_hugepage/hugepages-32kB/stats/swpout:347721 /sys/kernel/mm/transparent_hugepage/hugepages-32kB/stats/swpout_fallback:3110 /sys/kernel/mm/transparent_hugepage/hugepages-512kB/stats/swpout:3365 /sys/kernel/mm/transparent_hugepage/hugepages-512kB/stats/swpout_fallback:8269 /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/stats/swpout:24 /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/stats/swpout_fallback:3341 /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/stats/swpout:145 /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/stats/swpout_fallback:5038 /sys/kernel/mm/transparent_hugepage/hugepages-64kB/stats/swpout:322737 /sys/kernel/mm/transparent_hugepage/hugepages-64kB/stats/swpout_fallback:36808 /sys/kernel/mm/transparent_hugepage/hugepages-16kB/stats/swpout:380455 /sys/kernel/mm/transparent_hugepage/hugepages-16kB/stats/swpout_fallback:1010 /sys/kernel/mm/transparent_hugepage/hugepages-256kB/stats/swpout:24973 /sys/kernel/mm/transparent_hugepage/hugepages-256kB/stats/swpout_fallback:13223 /sys/kernel/mm/transparent_hugepage/hugepages-128kB/stats/swpout:197348 /sys/kernel/mm/transparent_hugepage/hugepages-128kB/stats/swpout_fallback:80541 Without: -------- 1794.41user 3151.29system 3:05.97elapsed 2659%CPU (0avgtext+0avgdata 846704maxresident)k 1810.27user 3304.48system 3:05.38elapsed 2759%CPU (0avgtext+0avgdata 846636maxresident)k 1809.84user 3254.85system 3:03.83elapsed 2755%CPU (0avgtext+0avgdata 846952maxresident)k 1813.54user 3259.56system 3:04.28elapsed 2752%CPU (0avgtext+0avgdata 846848maxresident)k 1829.97user 3338.40system 3:07.32elapsed 2759%CPU (0avgtext+0avgdata 847024maxresident)k Summary: User: 1811.61 System: 3261.72 : 3151.29 3304.48 3254.85 3259.56 3338.40 Real: 185.356 mTHP swapout status: hugepages-32kB/stats/swpout:35630 hugepages-32kB/stats/swpout_fallback:1809908 hugepages-512kB/stats/swpout:523 hugepages-512kB/stats/swpout_fallback:55235 hugepages-2048kB/stats/swpout:53 hugepages-2048kB/stats/swpout_fallback:17264 hugepages-1024kB/stats/swpout:85 hugepages-1024kB/stats/swpout_fallback:24979 hugepages-64kB/stats/swpout:30117 hugepages-64kB/stats/swpout_fallback:1825399 hugepages-16kB/stats/swpout:42775 hugepages-16kB/stats/swpout_fallback:1951123 hugepages-256kB/stats/swpout:2326 hugepages-256kB/stats/swpout_fallback:170165 hugepages-128kB/stats/swpout:17925 hugepages-128kB/stats/swpout_fallback:1309757 This patch (of 9): Previously, the swap cluster used a cluster index as a pointer to construct a custom single link list type "swap_cluster_list". The next cluster pointer is shared with the cluster->count. It prevents puting the non free cluster into a list. Change the cluster to use the standard double link list instead. This allows tracing the nonfull cluster in the follow up patch. That way, it is faster to get to the nonfull cluster of that order. Remove the cluster getter/setter for accessing the cluster struct member. The list operation is protected by the swap_info_struct->lock. Change cluster code to use "struct swap_cluster_info *" to reference the cluster rather than by using index. That is more consistent with the list manipulation. It avoids the repeat adding index to the cluser_info. The code is easier to understand. Remove the cluster next pointer is NULL flag, the double link list can handle the empty list pretty well. The "swap_cluster_info" struct is two pointer bigger, because 512 swap entries share one swap_cluster_info struct, it has very little impact on the average memory usage per swap entry. For 1TB swapfile, the swap cluster data structure increases from 8MB to 24MB. Other than the list conversion, there is no real function change in this patch. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-0-cb9c148b9297@kernel.org Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-1-cb9c148b9297@kernel.orgSigned-off-by: Chris Li <chrisl@kernel.org> Reported-by: Barry Song <21cnbao@gmail.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kairui Song <kasong@tencent.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: swap: swap cluster switch to double link list
Patch series "mm: swap: mTHP swap allocator base on swap cluster order", v5. This is the short term solutions "swap cluster order" listed in my "Swap Abstraction" discussion slice 8 in the recent LSF/MM conference. When commit 845982eb "mm: swap: allow storage of all mTHP orders" is introduced, it only allocates the mTHP swap entries from the new empty cluster list. It has a fragmentation issue reported by Barry. https://lore.kernel.org/all/CAGsJ_4zAcJkuW016Cfi6wicRr8N9X+GJJhgMQdSMp+Ah+NSgNQ@mail.gmail.com/ The reason is that all the empty clusters have been exhausted while there are plenty of free swap entries in the cluster that are not 100% free. Remember the swap allocation order in the cluster. Keep track of the per order non full cluster list for later allocation. This series gives the swap SSD allocation a new separate code path from the HDD allocation. The new allocator use cluster list only and do not global scan swap_map[] without lock any more. This streamline the swap allocation for SSD. The code matches the execution flow much better. User impact: For users that allocate and free mix order mTHP swapping, It greatly improves the success rate of the mTHP swap allocation after the initial phase. It also performs faster when the swapfile is close to full, because the allocator can get the non full cluster from a list rather than scanning a lot of swap_map entries. With Barry's mthp test program V2: Without: $ ./thp_swap_allocator_test -a Iteration 1: swpout inc: 32, swpout fallback inc: 192, Fallback percentage: 85.71% Iteration 2: swpout inc: 0, swpout fallback inc: 231, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 227, Fallback percentage: 100.00% ... Iteration 98: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 215, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% $ ./thp_swap_allocator_test -a -s Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% $ ./thp_swap_allocator_test -s Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% $ ./thp_swap_allocator_test Iteration 1: swpout inc: 0, swpout fallback inc: 224, Fallback percentage: 100.00% Iteration 2: swpout inc: 0, swpout fallback inc: 218, Fallback percentage: 100.00% Iteration 3: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% .. Iteration 98: swpout inc: 0, swpout fallback inc: 228, Fallback percentage: 100.00% Iteration 99: swpout inc: 0, swpout fallback inc: 230, Fallback percentage: 100.00% Iteration 100: swpout inc: 0, swpout fallback inc: 229, Fallback percentage: 100.00% With: # with all 0.00% filter out $ ./thp_swap_allocator_test -a | grep -v "0.00%" $ # all result are 0.00% $ ./thp_swap_allocator_test -a -s | grep -v "0.00%" ./thp_swap_allocator_test -a -s | grep -v "0.00%" Iteration 14: swpout inc: 223, swpout fallback inc: 3, Fallback percentage: 1.33% Iteration 19: swpout inc: 219, swpout fallback inc: 7, Fallback percentage: 3.10% Iteration 28: swpout inc: 225, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 29: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 34: swpout inc: 220, swpout fallback inc: 8, Fallback percentage: 3.51% Iteration 35: swpout inc: 222, swpout fallback inc: 11, Fallback percentage: 4.72% Iteration 38: swpout inc: 217, swpout fallback inc: 4, Fallback percentage: 1.81% Iteration 40: swpout inc: 222, swpout fallback inc: 6, Fallback percentage: 2.63% Iteration 42: swpout inc: 221, swpout fallback inc: 2, Fallback percentage: 0.90% Iteration 43: swpout inc: 215, swpout fallback inc: 7, Fallback percentage: 3.15% Iteration 47: swpout inc: 226, swpout fallback inc: 2, Fallback percentage: 0.88% Iteration 49: swpout inc: 217, swpout fallback inc: 1, Fallback percentage: 0.46% Iteration 52: swpout inc: 221, swpout fallback inc: 8, Fallback percentage: 3.49% Iteration 56: swpout inc: 224, swpout fallback inc: 4, Fallback percentage: 1.75% Iteration 58: swpout inc: 214, swpout fallback inc: 5, Fallback percentage: 2.28% Iteration 62: swpout inc: 220, swpout fallback inc: 3, Fallback percentage: 1.35% Iteration 64: swpout inc: 224, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 67: swpout inc: 221, swpout fallback inc: 1, Fallback percentage: 0.45% Iteration 75: swpout inc: 220, swpout fallback inc: 9, Fallback percentage: 3.93% Iteration 82: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 86: swpout inc: 211, swpout fallback inc: 12, Fallback percentage: 5.38% Iteration 89: swpout inc: 226, swpout fallback inc: 2, Fallback percentage: 0.88% Iteration 93: swpout inc: 220, swpout fallback inc: 1, Fallback percentage: 0.45% Iteration 94: swpout inc: 224, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 96: swpout inc: 221, swpout fallback inc: 6, Fallback percentage: 2.64% Iteration 98: swpout inc: 227, swpout fallback inc: 1, Fallback percentage: 0.44% Iteration 99: swpout inc: 227, swpout fallback inc: 3, Fallback percentage: 1.30% $ ./thp_swap_allocator_test ./thp_swap_allocator_test Iteration 1: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 131, swpout fallback inc: 101, Fallback percentage: 43.53% Iteration 3: swpout inc: 71, swpout fallback inc: 155, Fallback percentage: 68.58% Iteration 4: swpout inc: 55, swpout fallback inc: 168, Fallback percentage: 75.34% Iteration 5: swpout inc: 35, swpout fallback inc: 191, Fallback percentage: 84.51% Iteration 6: swpout inc: 25, swpout fallback inc: 199, Fallback percentage: 88.84% Iteration 7: swpout inc: 23, swpout fallback inc: 205, Fallback percentage: 89.91% Iteration 8: swpout inc: 9, swpout fallback inc: 219, Fallback percentage: 96.05% Iteration 9: swpout inc: 13, swpout fallback inc: 213, Fallback percentage: 94.25% Iteration 10: swpout inc: 12, swpout fallback inc: 216, Fallback percentage: 94.74% Iteration 11: swpout inc: 16, swpout fallback inc: 213, Fallback percentage: 93.01% Iteration 12: swpout inc: 10, swpout fallback inc: 210, Fallback percentage: 95.45% Iteration 13: swpout inc: 16, swpout fallback inc: 212, Fallback percentage: 92.98% Iteration 14: swpout inc: 12, swpout fallback inc: 212, Fallback percentage: 94.64% Iteration 15: swpout inc: 15, swpout fallback inc: 211, Fallback percentage: 93.36% Iteration 16: swpout inc: 15, swpout fallback inc: 200, Fallback percentage: 93.02% Iteration 17: swpout inc: 9, swpout fallback inc: 220, Fallback percentage: 96.07% $ ./thp_swap_allocator_test -s ./thp_swap_allocator_test -s Iteration 1: swpout inc: 233, swpout fallback inc: 0, Fallback percentage: 0.00% Iteration 2: swpout inc: 97, swpout fallback inc: 135, Fallback percentage: 58.19% Iteration 3: swpout inc: 42, swpout fallback inc: 192, Fallback percentage: 82.05% Iteration 4: swpout inc: 19, swpout fallback inc: 214, Fallback percentage: 91.85% Iteration 5: swpout inc: 12, swpout fallback inc: 213, Fallback percentage: 94.67% Iteration 6: swpout inc: 11, swpout fallback inc: 217, Fallback percentage: 95.18% Iteration 7: swpout inc: 9, swpout fallback inc: 214, Fallback percentage: 95.96% Iteration 8: swpout inc: 8, swpout fallback inc: 213, Fallback percentage: 96.38% Iteration 9: swpout inc: 2, swpout fallback inc: 223, Fallback percentage: 99.11% Iteration 10: swpout inc: 2, swpout fallback inc: 228, Fallback percentage: 99.13% Iteration 11: swpout inc: 4, swpout fallback inc: 214, Fallback percentage: 98.17% Iteration 12: swpout inc: 5, swpout fallback inc: 226, Fallback percentage: 97.84% Iteration 13: swpout inc: 3, swpout fallback inc: 212, Fallback percentage: 98.60% Iteration 14: swpout inc: 0, swpout fallback inc: 222, Fallback percentage: 100.00% Iteration 15: swpout inc: 3, swpout fallback inc: 222, Fallback percentage: 98.67% Iteration 16: swpout inc: 4, swpout fallback inc: 223, Fallback percentage: 98.24% ========= Kernel compile under tmpfs with cgroup memory.max = 470M. 12 core 24 hyperthreading, 32 jobs. 10 Run each group SSD swap 10 runs average, 20G swap partition: With: user 2929.064 system 1479.381 : 1376.89 1398.22 1444.64 1477.39 1479.04 1497.27 1504.47 1531.4 1532.92 1551.57 real 1441.324 Without: user 2910.872 system 1482.732 : 1440.01 1451.4 1462.01 1467.47 1467.51 1469.3 1470.19 1496.32 1544.1 1559.01 real 1580.822 Two zram swap: zram0 3.0G zram1 20G. The idea is forcing the zram0 almost full then overflow to zram1: With: user 4320.301 system 4272.403 : 4236.24 4262.81 4264.75 4269.13 4269.44 4273.06 4279.85 4285.98 4289.64 4293.13 real 431.759 Without user 4301.393 system 4387.672 : 4374.47 4378.3 4380.95 4382.84 4383.06 4388.05 4389.76 4397.16 4398.23 4403.9 real 433.979 ------ more test result from Kaiui ---------- Test with build linux kernel using a 4G ZRAM, 1G memory.max limit on top of shmem: System info: 32 Core AMD Zen2, 64G total memory. Test 3 times using only 4K pages: ================================= With: ----- 1838.74user 2411.21system 2:37.86elapsed 2692%CPU (0avgtext+0avgdata 847060maxresident)k 1839.86user 2465.77system 2:39.35elapsed 2701%CPU (0avgtext+0avgdata 847060maxresident)k 1840.26user 2454.68system 2:39.43elapsed 2693%CPU (0avgtext+0avgdata 847060maxresident)k Summary (~4.6% improment of system time): User: 1839.62 System: 2443.89: 2465.77 2454.68 2411.21 Real: 158.88 Without: -------- 1837.99user 2575.95system 2:43.09elapsed 2706%CPU (0avgtext+0avgdata 846520maxresident)k 1838.32user 2555.15system 2:42.52elapsed 2709%CPU (0avgtext+0avgdata 846520maxresident)k 1843.02user 2561.55system 2:43.35elapsed 2702%CPU (0avgtext+0avgdata 846520maxresident)k Summary: User: 1839.78 System: 2564.22: 2575.95 2555.15 2561.55 Real: 162.99 Test 5 times using enabled all mTHP pages: ========================================== With: ----- 1796.44user 2937.33system 2:59.09elapsed 2643%CPU (0avgtext+0avgdata 846936maxresident)k 1802.55user 3002.32system 2:54.68elapsed 2750%CPU (0avgtext+0avgdata 847072maxresident)k 1806.59user 2986.53system 2:55.17elapsed 2736%CPU (0avgtext+0avgdata 847092maxresident)k 1803.27user 2982.40system 2:54.49elapsed 2742%CPU (0avgtext+0avgdata 846796maxresident)k 1807.43user 3036.08system 2:56.06elapsed 2751%CPU (0avgtext+0avgdata 846488maxresident)k Summary (~8.4% improvement of system time): User: 1803.25 System: 2988.93: 2937.33 3002.32 2986.53 2982.40 3036.08 Real: 175.90 mTHP swapout status: /sys/kernel/mm/transparent_hugepage/hugepages-32kB/stats/swpout:347721 /sys/kernel/mm/transparent_hugepage/hugepages-32kB/stats/swpout_fallback:3110 /sys/kernel/mm/transparent_hugepage/hugepages-512kB/stats/swpout:3365 /sys/kernel/mm/transparent_hugepage/hugepages-512kB/stats/swpout_fallback:8269 /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/stats/swpout:24 /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/stats/swpout_fallback:3341 /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/stats/swpout:145 /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/stats/swpout_fallback:5038 /sys/kernel/mm/transparent_hugepage/hugepages-64kB/stats/swpout:322737 /sys/kernel/mm/transparent_hugepage/hugepages-64kB/stats/swpout_fallback:36808 /sys/kernel/mm/transparent_hugepage/hugepages-16kB/stats/swpout:380455 /sys/kernel/mm/transparent_hugepage/hugepages-16kB/stats/swpout_fallback:1010 /sys/kernel/mm/transparent_hugepage/hugepages-256kB/stats/swpout:24973 /sys/kernel/mm/transparent_hugepage/hugepages-256kB/stats/swpout_fallback:13223 /sys/kernel/mm/transparent_hugepage/hugepages-128kB/stats/swpout:197348 /sys/kernel/mm/transparent_hugepage/hugepages-128kB/stats/swpout_fallback:80541 Without: -------- 1794.41user 3151.29system 3:05.97elapsed 2659%CPU (0avgtext+0avgdata 846704maxresident)k 1810.27user 3304.48system 3:05.38elapsed 2759%CPU (0avgtext+0avgdata 846636maxresident)k 1809.84user 3254.85system 3:03.83elapsed 2755%CPU (0avgtext+0avgdata 846952maxresident)k 1813.54user 3259.56system 3:04.28elapsed 2752%CPU (0avgtext+0avgdata 846848maxresident)k 1829.97user 3338.40system 3:07.32elapsed 2759%CPU (0avgtext+0avgdata 847024maxresident)k Summary: User: 1811.61 System: 3261.72 : 3151.29 3304.48 3254.85 3259.56 3338.40 Real: 185.356 mTHP swapout status: hugepages-32kB/stats/swpout:35630 hugepages-32kB/stats/swpout_fallback:1809908 hugepages-512kB/stats/swpout:523 hugepages-512kB/stats/swpout_fallback:55235 hugepages-2048kB/stats/swpout:53 hugepages-2048kB/stats/swpout_fallback:17264 hugepages-1024kB/stats/swpout:85 hugepages-1024kB/stats/swpout_fallback:24979 hugepages-64kB/stats/swpout:30117 hugepages-64kB/stats/swpout_fallback:1825399 hugepages-16kB/stats/swpout:42775 hugepages-16kB/stats/swpout_fallback:1951123 hugepages-256kB/stats/swpout:2326 hugepages-256kB/stats/swpout_fallback:170165 hugepages-128kB/stats/swpout:17925 hugepages-128kB/stats/swpout_fallback:1309757 This patch (of 9): Previously, the swap cluster used a cluster index as a pointer to construct a custom single link list type "swap_cluster_list". The next cluster pointer is shared with the cluster->count. It prevents puting the non free cluster into a list. Change the cluster to use the standard double link list instead. This allows tracing the nonfull cluster in the follow up patch. That way, it is faster to get to the nonfull cluster of that order. Remove the cluster getter/setter for accessing the cluster struct member. The list operation is protected by the swap_info_struct->lock. Change cluster code to use "struct swap_cluster_info *" to reference the cluster rather than by using index. That is more consistent with the list manipulation. It avoids the repeat adding index to the cluser_info. The code is easier to understand. Remove the cluster next pointer is NULL flag, the double link list can handle the empty list pretty well. The "swap_cluster_info" struct is two pointer bigger, because 512 swap entries share one swap_cluster_info struct, it has very little impact on the average memory usage per swap entry. For 1TB swapfile, the swap cluster data structure increases from 8MB to 24MB. Other than the list conversion, there is no real function change in this patch. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-0-cb9c148b9297@kernel.org Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-1-cb9c148b9297@kernel.orgSigned-off-by: Chris Li <chrisl@kernel.org> Reported-by: Barry Song <21cnbao@gmail.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kairui Song <kasong@tencent.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
73ed0baa · Chris Li · Andrew Morton · 340afb80 · 73ed0baa · 73ed0baa
Commit 73ed0baa authored Jul 30, 2024 by Chris Li Committed by Andrew Morton Sep 03, 2024
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include/linux/swap.h include/linux/swap.h +9 -16

mm/swapfile.c mm/swapfile.c +62 -164

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--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -243,22 +243,20 @@ enum {
 * free clusters are organized into a list. We fetch an entry from the list to
 * get a free cluster.
 *
- * The data field stores next cluster if the cluster is free or cluster usage
- * counter otherwise. The flags field determines if a cluster is free. This is
- * protected by swap_info_struct.lock.
+ * The flags field determines if a cluster is free. This is
+ * protected by cluster lock.
 */
 struct swap_cluster_info {
 	spinlock_t lock;	/*
 				 * Protect swap_cluster_info fields
-				 * and swap_info_struct->swap_map
-				 * elements correspond to the swap
-				 * cluster
+				 * other than list, and swap_info_struct->swap_map
+				 * elements corresponding to the swap cluster.
 				 */
-	unsigned int data:24;
-	unsigned int flags:8;
+	u16 count;
+	u8 flags;
+	struct list_head list;
 };
 #define CLUSTER_FLAG_FREE 1 /* This cluster is free */
-#define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */

 /*
 * The first page in the swap file is the swap header, which is always marked
@@ -283,11 +281,6 @@ struct percpu_cluster {
 	unsigned int next[SWAP_NR_ORDERS]; /* Likely next allocation offset */
 };

-struct swap_cluster_list {
-	struct swap_cluster_info head;
-	struct swap_cluster_info tail;
-};
-
 /*
 * The in-memory structure used to track swap areas.
 */
@@ -300,7 +293,7 @@ struct swap_info_struct {
 	unsigned int	max;		/* extent of the swap_map */
 	unsigned char *swap_map;	/* vmalloc'ed array of usage counts */
 	struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
-	struct swap_cluster_list free_clusters; /* free clusters list */
+	struct list_head free_clusters; /* free clusters list */
 	unsigned int lowest_bit;	/* index of first free in swap_map */
 	unsigned int highest_bit;	/* index of last free in swap_map */
 	unsigned int pages;		/* total of usable pages of swap */
@@ -331,7 +324,7 @@ struct swap_info_struct {
 					 * list.
 					 */
 	struct work_struct discard_work; /* discard worker */
-	struct swap_cluster_list discard_clusters; /* discard clusters list */
+	struct list_head discard_clusters; /* discard clusters list */
 	struct plist_node avail_lists[]; /*
 					   * entries in swap_avail_heads, one
 					   * entry per node.

--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -290,62 +290,15 @@ static void discard_swap_cluster(struct swap_info_struct *si,
 #endif
 #define LATENCY_LIMIT		256

-static inline void cluster_set_flag(struct swap_cluster_info *info,
-	unsigned int flag)
-{
-	info->flags = flag;
-}
-
-static inline unsigned int cluster_count(struct swap_cluster_info *info)
-{
-	return info->data;
-}
-
-static inline void cluster_set_count(struct swap_cluster_info *info,
-				     unsigned int c)
-{
-	info->data = c;
-}
-
-static inline void cluster_set_count_flag(struct swap_cluster_info *info,
-					 unsigned int c, unsigned int f)
-{
-	info->flags = f;
-	info->data = c;
-}
-
-static inline unsigned int cluster_next(struct swap_cluster_info *info)
-{
-	return info->data;
-}
-
-static inline void cluster_set_next(struct swap_cluster_info *info,
-				    unsigned int n)
-{
-	info->data = n;
-}
-
-static inline void cluster_set_next_flag(struct swap_cluster_info *info,
-					 unsigned int n, unsigned int f)
-{
-	info->flags = f;
-	info->data = n;
-}
-
 static inline bool cluster_is_free(struct swap_cluster_info *info)
 {
 	return info->flags & CLUSTER_FLAG_FREE;
 }

-static inline bool cluster_is_null(struct swap_cluster_info *info)
-{
-	return info->flags & CLUSTER_FLAG_NEXT_NULL;
-}
-
-static inline void cluster_set_null(struct swap_cluster_info *info)
+static inline unsigned int cluster_index(struct swap_info_struct *si,
+					 struct swap_cluster_info *ci)
 {
-	info->flags = CLUSTER_FLAG_NEXT_NULL;
-	info->data = 0;
+	return ci - si->cluster_info;
 }

 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
@@ -394,65 +347,11 @@ static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si,
 		spin_unlock(&si->lock);
 }

-static inline bool cluster_list_empty(struct swap_cluster_list *list)
-{
-	return cluster_is_null(&list->head);
-}
-
-static inline unsigned int cluster_list_first(struct swap_cluster_list *list)
-{
-	return cluster_next(&list->head);
-}
-
-static void cluster_list_init(struct swap_cluster_list *list)
-{
-	cluster_set_null(&list->head);
-	cluster_set_null(&list->tail);
-}
-
-static void cluster_list_add_tail(struct swap_cluster_list *list,
-				  struct swap_cluster_info *ci,
-				  unsigned int idx)
-{
-	if (cluster_list_empty(list)) {
-		cluster_set_next_flag(&list->head, idx, 0);
-		cluster_set_next_flag(&list->tail, idx, 0);
-	} else {
-		struct swap_cluster_info *ci_tail;
-		unsigned int tail = cluster_next(&list->tail);
-
-		/*
-		 * Nested cluster lock, but both cluster locks are
-		 * only acquired when we held swap_info_struct->lock
-		 */
-		ci_tail = ci + tail;
-		spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING);
-		cluster_set_next(ci_tail, idx);
-		spin_unlock(&ci_tail->lock);
-		cluster_set_next_flag(&list->tail, idx, 0);
-	}
-}
-
-static unsigned int cluster_list_del_first(struct swap_cluster_list *list,
-					   struct swap_cluster_info *ci)
-{
-	unsigned int idx;
-
-	idx = cluster_next(&list->head);
-	if (cluster_next(&list->tail) == idx) {
-		cluster_set_null(&list->head);
-		cluster_set_null(&list->tail);
-	} else
-		cluster_set_next_flag(&list->head,
-				      cluster_next(&ci[idx]), 0);
-
-	return idx;
-}
-
 /* Add a cluster to discard list and schedule it to do discard */
 static void swap_cluster_schedule_discard(struct swap_info_struct *si,
-		unsigned int idx)
+		struct swap_cluster_info *ci)
 {
+	unsigned int idx = cluster_index(si, ci);
 	/*
 	 * If scan_swap_map_slots() can't find a free cluster, it will check
 	 * si->swap_map directly. To make sure the discarding cluster isn't
@@ -462,17 +361,14 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
 	memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 			SWAP_MAP_BAD, SWAPFILE_CLUSTER);

-	cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx);
-
+	list_add_tail(&ci->list, &si->discard_clusters);
 	schedule_work(&si->discard_work);
 }

-static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
+static void __free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci)
 {
-	struct swap_cluster_info *ci = si->cluster_info;
-
-	cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE);
-	cluster_list_add_tail(&si->free_clusters, ci, idx);
+	ci->flags = CLUSTER_FLAG_FREE;
+	list_add_tail(&ci->list, &si->free_clusters);
 }

 /*
@@ -481,24 +377,25 @@ static void __free_cluster(struct swap_info_struct *si, unsigned long idx)
 */
 static void swap_do_scheduled_discard(struct swap_info_struct *si)
 {
-	struct swap_cluster_info *info, *ci;
+	struct swap_cluster_info *ci;
 	unsigned int idx;

-	info = si->cluster_info;
-
-	while (!cluster_list_empty(&si->discard_clusters)) {
-		idx = cluster_list_del_first(&si->discard_clusters, info);
+	while (!list_empty(&si->discard_clusters)) {
+		ci = list_first_entry(&si->discard_clusters, struct swap_cluster_info, list);
+		list_del(&ci->list);
+		idx = cluster_index(si, ci);
 		spin_unlock(&si->lock);

 		discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
 				SWAPFILE_CLUSTER);

 		spin_lock(&si->lock);
-		ci = lock_cluster(si, idx * SWAPFILE_CLUSTER);
-		__free_cluster(si, idx);
+
+		spin_lock(&ci->lock);
+		__free_cluster(si, ci);
 		memset(si->swap_map + idx * SWAPFILE_CLUSTER,
 				0, SWAPFILE_CLUSTER);
-		unlock_cluster(ci);
+		spin_unlock(&ci->lock);
 	}
 }

@@ -521,20 +418,21 @@ static void swap_users_ref_free(struct percpu_ref *ref)
 	complete(&si->comp);
 }

-static void alloc_cluster(struct swap_info_struct *si, unsigned long idx)
+static struct swap_cluster_info *alloc_cluster(struct swap_info_struct *si, unsigned long idx)
 {
-	struct swap_cluster_info *ci = si->cluster_info;
+	struct swap_cluster_info *ci = list_first_entry(&si->free_clusters,
+							struct swap_cluster_info, list);

-	VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx);
-	cluster_list_del_first(&si->free_clusters, ci);
-	cluster_set_count_flag(ci + idx, 0, 0);
+	VM_BUG_ON(cluster_index(si, ci) != idx);
+	list_del(&ci->list);
+	ci->count = 0;
+	ci->flags = 0;
+	return ci;
 }

-static void free_cluster(struct swap_info_struct *si, unsigned long idx)
+static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *ci)
 {
-	struct swap_cluster_info *ci = si->cluster_info + idx;
-
-	VM_BUG_ON(cluster_count(ci) != 0);
+	VM_BUG_ON(ci->count != 0);
 	/*
 	 * If the swap is discardable, prepare discard the cluster
 	 * instead of free it immediately. The cluster will be freed
@@ -542,11 +440,11 @@ static void free_cluster(struct swap_info_struct *si, unsigned long idx)
 	 */
 	if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
 	    (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
-		swap_cluster_schedule_discard(si, idx);
+		swap_cluster_schedule_discard(si, ci);
 		return;
 	}

-	__free_cluster(si, idx);
+	__free_cluster(si, ci);
 }

 /*
@@ -559,15 +457,15 @@ static void add_cluster_info_page(struct swap_info_struct *p,
 	unsigned long count)
 {
 	unsigned long idx = page_nr / SWAPFILE_CLUSTER;
+	struct swap_cluster_info *ci = cluster_info + idx;

 	if (!cluster_info)
 		return;
-	if (cluster_is_free(&cluster_info[idx]))
+	if (cluster_is_free(ci))
 		alloc_cluster(p, idx);

-	VM_BUG_ON(cluster_count(&cluster_info[idx]) + count > SWAPFILE_CLUSTER);
-	cluster_set_count(&cluster_info[idx],
-		cluster_count(&cluster_info[idx]) + count);
+	VM_BUG_ON(ci->count + count > SWAPFILE_CLUSTER);
+	ci->count += count;
 }

 /*
@@ -581,24 +479,20 @@ static void inc_cluster_info_page(struct swap_info_struct *p,
 }

 /*
- * The cluster corresponding to page_nr decreases one usage. If the usage
- * counter becomes 0, which means no page in the cluster is in using, we can
- * optionally discard the cluster and add it to free cluster list.
+ * The cluster ci decreases one usage. If the usage counter becomes 0,
+ * which means no page in the cluster is in use, we can optionally discard
+ * the cluster and add it to free cluster list.
 */
-static void dec_cluster_info_page(struct swap_info_struct *p,
-	struct swap_cluster_info *cluster_info, unsigned long page_nr)
+static void dec_cluster_info_page(struct swap_info_struct *p, struct swap_cluster_info *ci)
 {
-	unsigned long idx = page_nr / SWAPFILE_CLUSTER;
-
-	if (!cluster_info)
+	if (!p->cluster_info)
 		return;

-	VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0);
-	cluster_set_count(&cluster_info[idx],
-		cluster_count(&cluster_info[idx]) - 1);
+	VM_BUG_ON(ci->count == 0);
+	ci->count--;

-	if (cluster_count(&cluster_info[idx]) == 0)
-		free_cluster(p, idx);
+	if (!ci->count)
+		free_cluster(p, ci);
 }

 /*
@@ -611,10 +505,12 @@ scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
 {
 	struct percpu_cluster *percpu_cluster;
 	bool conflict;
+	struct swap_cluster_info *first = list_first_entry(&si->free_clusters,
+							   struct swap_cluster_info, list);

 	offset /= SWAPFILE_CLUSTER;
-	conflict = !cluster_list_empty(&si->free_clusters) &&
-		offset != cluster_list_first(&si->free_clusters) &&
+	conflict = !list_empty(&si->free_clusters) &&
+		offset !=  cluster_index(si, first) &&
 		cluster_is_free(&si->cluster_info[offset]);

 	if (!conflict)
@@ -655,10 +551,10 @@ static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
 	cluster = this_cpu_ptr(si->percpu_cluster);
 	tmp = cluster->next[order];
 	if (tmp == SWAP_NEXT_INVALID) {
-		if (!cluster_list_empty(&si->free_clusters)) {
-			tmp = cluster_next(&si->free_clusters.head) *
-					SWAPFILE_CLUSTER;
-		} else if (!cluster_list_empty(&si->discard_clusters)) {
+		if (!list_empty(&si->free_clusters)) {
+			ci = list_first_entry(&si->free_clusters, struct swap_cluster_info, list);
+			tmp = cluster_index(si, ci) * SWAPFILE_CLUSTER;
+		} else if (!list_empty(&si->discard_clusters)) {
 			/*
 			 * we don't have free cluster but have some clusters in
 			 * discarding, do discard now and reclaim them, then
@@ -1062,8 +958,9 @@ static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)

 	ci = lock_cluster(si, offset);
 	memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER);
-	cluster_set_count_flag(ci, 0, 0);
-	free_cluster(si, idx);
+	ci->count = 0;
+	ci->flags = 0;
+	free_cluster(si, ci);
 	unlock_cluster(ci);
 	swap_range_free(si, offset, SWAPFILE_CLUSTER);
 }
@@ -1336,7 +1233,7 @@ static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry)
 	count = p->swap_map[offset];
 	VM_BUG_ON(count != SWAP_HAS_CACHE);
 	p->swap_map[offset] = 0;
-	dec_cluster_info_page(p, p->cluster_info, offset);
+	dec_cluster_info_page(p, ci);
 	unlock_cluster(ci);

 	mem_cgroup_uncharge_swap(entry, 1);
@@ -3011,8 +2908,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,

 	nr_good_pages = maxpages - 1;	/* omit header page */

-	cluster_list_init(&p->free_clusters);
-	cluster_list_init(&p->discard_clusters);
+	INIT_LIST_HEAD(&p->free_clusters);
+	INIT_LIST_HEAD(&p->discard_clusters);

 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
 		unsigned int page_nr = swap_header->info.badpages[i];
@@ -3063,14 +2960,15 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
 	for (k = 0; k < SWAP_CLUSTER_COLS; k++) {
 		j = (k + col) % SWAP_CLUSTER_COLS;
 		for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) {
+			struct swap_cluster_info *ci;
 			idx = i * SWAP_CLUSTER_COLS + j;
+			ci = cluster_info + idx;
 			if (idx >= nr_clusters)
 				continue;
-			if (cluster_count(&cluster_info[idx]))
+			if (ci->count)
 				continue;
-			cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
-			cluster_list_add_tail(&p->free_clusters, cluster_info,
-					      idx);
+			ci->flags = CLUSTER_FLAG_FREE;
+			list_add_tail(&ci->list, &p->free_clusters);
 		}
 	}
 	return nr_extents;