- 25 Oct, 2023 40 commits
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Qi Zheng authored
Patch series "handle memoryless nodes more appropriately", v3. Currently, in the process of initialization or offline memory, memoryless nodes will still be built into the fallback list of itself or other nodes. This is not what we expected, so this patch series removes memoryless nodes from the fallback list entirely. This patch (of 2): In find_next_best_node(), we skipped the memoryless nodes when building the zonelists of other normal nodes (N_NORMAL), but did not skip the memoryless node itself when building the zonelist. This will cause it to be traversed at runtime. For example, say we have node0 and node1, node0 is memoryless node, then the fallback order of node0 and node1 as follows: [ 0.153005] Fallback order for Node 0: 0 1 [ 0.153564] Fallback order for Node 1: 1 After this patch, we skip memoryless node0 entirely, then the fallback order of node0 and node1 as follows: [ 0.155236] Fallback order for Node 0: 1 [ 0.155806] Fallback order for Node 1: 1 So it becomes completely invisible, which will reduce runtime overhead. And in this way, we will not try to allocate pages from memoryless node0, then the panic mentioned in [1] will also be fixed. Even though this problem has been solved by dropping the NODE_MIN_SIZE constrain in x86 [2], it would be better to fix it in core MM as well. [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ [2]. https://lore.kernel.org/all/20231017062215.171670-1-rppt@kernel.org/ [zhengqi.arch@bytedance.com: update comment, per Ingo] Link: https://lkml.kernel.org/r/7300fc00a057eefeb9a68c8ad28171c3f0ce66ce.1697799303.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/cover.1697799303.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/cover.1697711415.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/157013e978468241de4a4c05d5337a44638ecb0e.1697711415.git.zhengqi.arch@bytedance.comSigned-off-by:
Qi Zheng <zhengqi.arch@bytedance.com> Acked-by:
David Hildenbrand <david@redhat.com> Acked-by:
Ingo Molnar <mingo@kernel.org> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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Zi Yan authored
Add nr_split to trace_mm_migrate_pages for large folio (including THP) split events. [akpm@linux-foundation.org: cleanup per Huang, Ying] Link: https://lkml.kernel.org/r/20231017163129.2025214-2-zi.yan@sent.comSigned-off-by:
Zi Yan <ziy@nvidia.com> Reviewed-by:
"Huang, Ying" <ying.huang@intel.com> Reviewed-by:
Baolin Wang <baolin.wang@linux.alibaba.com> Cc: David Hildenbrand <david@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by:
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Zi Yan authored
nr_failed was missing the large folio splits from migrate_pages_batch() and can cause a mismatch between migrate_pages() return value and the number of not migrated pages, i.e., when the return value of migrate_pages() is 0, there are still pages left in the from page list. It will happen when a non-PMD THP large folio fails to migrate due to -ENOMEM and is split successfully but not all the split pages are not migrated, migrate_pages_batch() would return non-zero, but astats.nr_thp_split = 0. nr_failed would be 0 and returned to the caller of migrate_pages(), but the not migrated pages are left in the from page list without being added back to LRU lists. Fix it by adding a new nr_split counter for large folio splits and adding it to nr_failed in migrate_page_sync() after migrate_pages_batch() is done. Link: https://lkml.kernel.org/r/20231017163129.2025214-1-zi.yan@sent.com Fixes: 2ef7dbb2 ("migrate_pages: try migrate in batch asynchronously firstly") Signed-off-by:
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Liu Shixin authored
In patch (mm: kmemleak: split __create_object into two functions), the initialisation of object has been splited in two places. Catalin said it feels a bit weird and error prone. So leave __alloc_object() to just do the actual allocation and let __link_object() do the full initialisation. Link: https://lkml.kernel.org/r/20231023025125.90972-1-liushixin2@huawei.comSigned-off-by:
Liu Shixin <liushixin2@huawei.com> Suggested-by:
Catalin Marinas <catalin.marinas@arm.com> Signed-off-by:
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Liu Shixin authored
delete_object_part() can be called by multiple callers in the same time. If an object is found and removed by a caller, and then another caller try to find it too, it failed and return directly. It still be recorded by kmemleak even if it has already been freed to buddy. With DEBUG on, kmemleak will report the following warning, kmemleak: Partially freeing unknown object at 0xa1af86000 (size 4096) CPU: 0 PID: 742 Comm: test_huge Not tainted 6.6.0-rc3kmemleak+ #54 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x37/0x50 kmemleak_free_part_phys+0x50/0x60 hugetlb_vmemmap_optimize+0x172/0x290 ? __pfx_vmemmap_remap_pte+0x10/0x10 __prep_new_hugetlb_folio+0xe/0x30 prep_new_hugetlb_folio.isra.0+0xe/0x40 alloc_fresh_hugetlb_folio+0xc3/0xd0 alloc_surplus_hugetlb_folio.constprop.0+0x6e/0xd0 hugetlb_acct_memory.part.0+0xe6/0x2a0 hugetlb_reserve_pages+0x110/0x2c0 hugetlbfs_file_mmap+0x11d/0x1b0 mmap_region+0x248/0x9a0 ? hugetlb_get_unmapped_area+0x15c/0x2d0 do_mmap+0x38b/0x580 vm_mmap_pgoff+0xe6/0x190 ksys_mmap_pgoff+0x18a/0x1f0 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Expand __create_object() and move __alloc_object() to the beginning. Then use kmemleak_lock to protect __find_and_remove_object() and __link_object() as a whole, which can guarantee all objects are processed sequentialally. Link: https://lkml.kernel.org/r/20231018102952.3339837-8-liushixin2@huawei.com Fixes: 53238a60 ("kmemleak: Allow partial freeing of memory blocks") Signed-off-by:
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Liu Shixin authored
Add new __find_and_remove_object() without kmemleak_lock protect, it is in preparation for the next patch. Link: https://lkml.kernel.org/r/20231018102952.3339837-7-liushixin2@huawei.comSigned-off-by:
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Liu Shixin authored
The kmemleak object is allocated by mem_pool_alloc(), which could be from slab or mem_pool[], so it's not suitable using __kmem_cache_free() to free the object, use __mem_pool_free() instead. Link: https://lkml.kernel.org/r/20231018102952.3339837-6-liushixin2@huawei.com Fixes: 0647398a ("mm: kmemleak: simple memory allocation pool for kmemleak objects") Signed-off-by:
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Liu Shixin authored
__create_object() consists of two part, the first part allocate a kmemleak object and initialize it, the second part insert it into object tree. This function need kmemleak_lock but actually only the second part need lock. Split it into two functions, the first function __alloc_object only allocate a kmemleak object, and the second function __link_object() will initialize the object and insert it into object tree, use the kmemleak_lock to protect __link_object() only. [akpm@linux-foundation.org: coding-style cleanups] Link: https://lkml.kernel.org/r/20231018102952.3339837-5-liushixin2@huawei.comSigned-off-by:
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Liu Shixin authored
With 0x%p, the pointer will be hashed and print (____ptrval____) instead. And with 0x%pa, the pointer can be successfully printed but with duplicate prefixes, which looks like: kmemleak: kmemleak_free(0x(____ptrval____)) kmemleak: kmemleak_free_percpu(0x(____ptrval____)) kmemleak: kmemleak_free_part_phys(0x0x0000000a1af86000) Use 0x%px instead of 0x%p or 0x%pa to print the pointer. Then the print will be like: kmemleak: kmemleak_free(0xffff9111c145b020) kmemleak: kmemleak_free_percpu(0x00000000000333b0) kmemleak: kmemleak_free_part_phys(0x0000000a1af80000) Link: https://lkml.kernel.org/r/20231018102952.3339837-4-liushixin2@huawei.comSigned-off-by:
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Liu Shixin authored
Since kmemleak_alloc_phys() rather than kmemleak_alloc() was called from memblock_alloc_range_nid(), kmemleak_free_part_phys() should be used to delete kmemleak object in free_bootmem_page(). In debug mode, there are following warning: kmemleak: Partially freeing unknown object at 0xffff97345aff7000 (size 4096) Link: https://lkml.kernel.org/r/20231018102952.3339837-3-liushixin2@huawei.com Fixes: 028725e7 ("bootmem: remove the vmemmap pages from kmemleak in free_bootmem_page") Signed-off-by:
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Liu Shixin authored
Patch series "Some bugfix about kmemleak", v3. Some bugfixes for kmemleak and the printed info from debug mode. This patch (of 7): Since kmemleak_alloc_phys() rather than kmemleak_alloc() was called from memblock_alloc_range_nid(), kmemleak_free_part_phys() should be used to delete kmemleak object in put_page_bootmem(). In debug mode, there are following warning: kmemleak: Partially freeing unknown object at 0xffff97345aff7000 (size 4096) Link: https://lkml.kernel.org/r/20231018102952.3339837-1-liushixin2@huawei.com Link: https://lkml.kernel.org/r/20231018102952.3339837-2-liushixin2@huawei.com Fixes: dd0ff4d1 ("bootmem: remove the vmemmap pages from kmemleak in put_page_bootmem") Signed-off-by:
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Kefeng Wang authored
Since all calls use folio_xchg_last_cpupid(), remove page_cpupid_xchg_last(). Link: https://lkml.kernel.org/r/20231018140806.2783514-20-wangkefeng.wang@huawei.comSigned-off-by:
Kefeng Wang <wangkefeng.wang@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by:
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Kefeng Wang authored
Convert to use folio_xchg_last_cpupid() in wp_page_reuse(), and remove page variable. Since now only normal and PMD-mapped page is handled by numa balancing, it's enough to only update the entire folio's last cpupid. Link: https://lkml.kernel.org/r/20231018140806.2783514-19-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Saves one compound_head() call, also in preparation for page_cpupid_xchg_last() conversion. Link: https://lkml.kernel.org/r/20231018140806.2783514-18-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Make finish_mkwrite_fault static since it is not used outside of memory.c. Link: https://lkml.kernel.org/r/20231018140806.2783514-17-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_xchg_last_cpupid() in __split_huge_page_tail(). Link: https://lkml.kernel.org/r/20231018140806.2783514-16-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_xchg_last_cpupid() in folio_migrate_flags(), also directly use folio_nid() instead of page_to_nid(&folio->page). Link: https://lkml.kernel.org/r/20231018140806.2783514-15-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_xchg_last_cpupid() in should_numa_migrate_memory(). Link: https://lkml.kernel.org/r/20231018140806.2783514-14-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Add folio_xchg_last_cpupid() wrapper, which is required to convert page_cpupid_xchg_last() to folio vertion later in the series. Link: https://lkml.kernel.org/r/20231018140806.2783514-13-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Since all calls use folio_xchg_access_time(), remove xchg_page_access_time(). Link: https://lkml.kernel.org/r/20231018140806.2783514-12-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Use a folio in change_huge_pmd(), which helps to remove last xchg_page_access_time() caller. Link: https://lkml.kernel.org/r/20231018140806.2783514-11-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Use a folio in change_pte_range() to save three compound_head() calls. Since now only normal and PMD-mapped page is handled by numa balancing, it is enough to only update the entire folio's access time. Link: https://lkml.kernel.org/r/20231018140806.2783514-10-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_xchg_access_time() in numa_hint_fault_latency(). Link: https://lkml.kernel.org/r/20231018140806.2783514-9-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Add folio_xchg_access_time() wrapper, which is required to convert xchg_page_access_time() to folio vertion later in the series. Link: https://lkml.kernel.org/r/20231018140806.2783514-8-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Since all calls use folio_last_cpupid(), remove page_cpupid_last(). Link: https://lkml.kernel.org/r/20231018140806.2783514-7-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_last_cpupid() in __split_huge_page_tail(). Link: https://lkml.kernel.org/r/20231018140806.2783514-6-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_last_cpupid() in do_huge_pmd_numa_page(). Link: https://lkml.kernel.org/r/20231018140806.2783514-5-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Convert to use folio_last_cpupid() in do_numa_page(). Link: https://lkml.kernel.org/r/20231018140806.2783514-4-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Add folio_last_cpupid() wrapper, which is required to convert page_cpupid_last() to folio vertion later in the series. Link: https://lkml.kernel.org/r/20231018140806.2783514-3-wangkefeng.wang@huawei.comSigned-off-by:
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Kefeng Wang authored
Patch series "mm: convert page cpupid functions to folios", v3. The cpupid(or access time) used by numa balancing is stored in flags or _last_cpupid(if LAST_CPUPID_NOT_IN_PAGE_FLAGS) of page, this is to convert page cpupid to folio cpupid, a new _last_cpupid is added into folio, which make us to use folio->_last_cpupid directly, and the page cpupid functions are converted to folio ones. page_cpupid_last() -> folio_last_cpupid() xchg_page_access_time() -> folio_xchg_access_time() page_cpupid_xchg_last() -> folio_xchg_last_cpupid() This patch (of 19): If WANT_PAGE_VIRTUAL and LAST_CPUPID_NOT_IN_PAGE_FLAGS defined, the 'virtual' and '_last_cpupid' are in struct page, and since _last_cpupid is used by numa balancing feature, it is better to move it before KMSAN metadata from struct page, also add them into struct folio to make us to access them from folio directly. Link: https://lkml.kernel.org/r/20231018140806.2783514-1-wangkefeng.wang@huawei.com Link: https://lkml.kernel.org/r/20231018140806.2783514-2-wangkefeng.wang@huawei.comSigned-off-by:
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Kairui Song authored
A variable is never used for swapout path (shadowp is NULL) and compiler is unable to optimize out the unneeded load since it's a function call. The was introduced by 3852f676 ("mm/swapcache: support to handle the shadow entries"). Link: https://lkml.kernel.org/r/20231017011728.37508-1-ryncsn@gmail.comSigned-off-by:
Kairui Song <kasong@tencent.com> Reviewed-by:
Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by:
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Roman Gushchin authored
Reimplement get_obj_cgroup_from_current() using current_obj_cgroup(). get_obj_cgroup_from_current() and current_obj_cgroup() share 80% of the code, so the new implementation is almost trivial. get_obj_cgroup_from_current() is a convenient function used by the bpf subsystem, so there is no reason to get rid of it completely. Link: https://lkml.kernel.org/r/20231019225346.1822282-7-roman.gushchin@linux.devSigned-off-by:
Roman Gushchin (Cruise) <roman.gushchin@linux.dev> Reviewed-by:
Vlastimil Babka <vbabka@suse.cz> Acked-by:
Shakeel Butt <shakeelb@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by:
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Roman Gushchin authored
Similar to slab and kmem, switch to a scope-based protection of the objcg pointer to avoid. Link: https://lkml.kernel.org/r/20231019225346.1822282-6-roman.gushchin@linux.devSigned-off-by:
Naresh Kamboju <naresh.kamboju@linaro.org> Acked-by:
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Roman Gushchin authored
Switch to a scope-based protection of the objcg pointer on slab/kmem allocation paths. Instead of using the get_() semantics in the pre-allocation hook and put the reference afterwards, let's rely on the fact that objcg is pinned by the scope. It's possible because: 1) if the objcg is received from the current task struct, the task is keeping a reference to the objcg. 2) if the objcg is received from an active memcg (remote charging), the memcg is pinned by the scope and has a reference to the corresponding objcg. Link: https://lkml.kernel.org/r/20231019225346.1822282-5-roman.gushchin@linux.devSigned-off-by:
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Roman Gushchin authored
Keep a reference to the original objcg object for the entire life of a memcg structure. This allows to simplify the synchronization on the kernel memory allocation paths: pinning a (live) memcg will also pin the corresponding objcg. The memory overhead of this change is minimal because object cgroups usually outlive their corresponding memory cgroups even without this change, so it's only an additional pointer per memcg. Link: https://lkml.kernel.org/r/20231019225346.1822282-4-roman.gushchin@linux.devSigned-off-by:
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Roman Gushchin authored
To charge a freshly allocated kernel object to a memory cgroup, the kernel needs to obtain an objcg pointer. Currently it does it indirectly by obtaining the memcg pointer first and then calling to __get_obj_cgroup_from_memcg(). Usually tasks spend their entire life belonging to the same object cgroup. So it makes sense to save the objcg pointer on task_struct directly, so it can be obtained faster. It requires some work on fork, exit and cgroup migrate paths, but these paths are way colder. To avoid any costly synchronization the following rules are applied: 1) A task sets it's objcg pointer itself. 2) If a task is being migrated to another cgroup, the least significant bit of the objcg pointer is set atomically. 3) On the allocation path the objcg pointer is obtained locklessly using the READ_ONCE() macro and the least significant bit is checked. If it's set, the following procedure is used to update it locklessly: - task->objcg is zeroed using cmpxcg - new objcg pointer is obtained - task->objcg is updated using try_cmpxchg - operation is repeated if try_cmpxcg fails It guarantees that no updates will be lost if task migration is racing against objcg pointer update. It also allows to keep both read and write paths fully lockless. Because the task is keeping a reference to the objcg, it can't go away while the task is alive. This commit doesn't change the way the remote memcg charging works. Link: https://lkml.kernel.org/r/20231019225346.1822282-3-roman.gushchin@linux.devSigned-off-by:Johannes Weiner <hannes@cmpxchg.org> Acked-by:
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Roman Gushchin authored
Patch series "mm: improve performance of accounted kernel memory allocations", v5. This patchset improves the performance of accounted kernel memory allocations by ~30% as measured by a micro-benchmark [1]. The benchmark is very straightforward: 1M of 64 bytes-large kmalloc() allocations. Below are results with the disabled kernel memory accounting, the original state and with this patchset applied. | | Kmem disabled | Original | Patched | Delta | |-------------+---------------+----------+---------+--------| | User cgroup | 29764 | 84548 | 59078 | -30.0% | | Root cgroup | 29742 | 48342 | 31501 | -34.8% | As we can see, the patchset removes the majority of the overhead when there is no actual accounting (a task belongs to the root memory cgroup) and almost halves the accounting overhead otherwise. The main idea is to get rid of unnecessary memcg to objcg conversions and switch to a scope-based protection of objcgs, which eliminates extra operations with objcg reference counters under a rcu read lock. More details are provided in individual commit descriptions. This patch (of 5): Manually inline memcg_kmem_bypass() and active_memcg() to speed up get_obj_cgroup_from_current() by avoiding duplicate in_task() checks and active_memcg() readings. Also add a likely() macro to __get_obj_cgroup_from_memcg(): obj_cgroup_tryget() should succeed at almost all times except a very unlikely race with the memcg deletion path. Link: https://lkml.kernel.org/r/20231019225346.1822282-1-roman.gushchin@linux.dev Link: https://lkml.kernel.org/r/20231019225346.1822282-2-roman.gushchin@linux.devSigned-off-by:
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Huang Ying authored
In current PCP auto-tuning design, if the number of pages allocated is much more than that of pages freed on a CPU, the PCP high may become the maximal value even if the allocating/freeing depth is small, for example, in the sender of network workloads. If a CPU was used as sender originally, then it is used as receiver after context switching, we need to fill the whole PCP with maximal high before triggering PCP draining for consecutive high order freeing. This will hurt the performance of some network workloads. To solve the issue, in this patch, we will track the consecutive page freeing with a counter in stead of relying on PCP draining. So, we can detect consecutive page freeing much earlier. On a 2-socket Intel server with 128 logical CPU, we tested SCTP_STREAM_MANY test case of netperf test suite with 64-pair processes. With the patch, the network bandwidth improves 5.0%. This restores the performance drop caused by PCP auto-tuning. Link: https://lkml.kernel.org/r/20231016053002.756205-10-ying.huang@intel.comSigned-off-by:
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Huang Ying authored
One target of PCP is to minimize pages in PCP if the system free pages is too few. To reach that target, when page reclaiming is active for the zone (ZONE_RECLAIM_ACTIVE), we will stop increasing PCP high in allocating path, decrease PCP high and free some pages in freeing path. But this may be too late because the background page reclaiming may introduce latency for some workloads. So, in this patch, during page allocation we will detect whether the number of free pages of the zone is below high watermark. If so, we will stop increasing PCP high in allocating path, decrease PCP high and free some pages in freeing path. With this, we can reduce the possibility of the premature background page reclaiming caused by too large PCP. The high watermark checking is done in allocating path to reduce the overhead in hotter freeing path. Link: https://lkml.kernel.org/r/20231016053002.756205-9-ying.huang@intel.comSigned-off-by:
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Huang Ying authored
The target to tune PCP high automatically is as follows, - Minimize allocation/freeing from/to shared zone - Minimize idle pages in PCP - Minimize pages in PCP if the system free pages is too few To reach these target, a tuning algorithm as follows is designed, - When we refill PCP via allocating from the zone, increase PCP high. Because if we had larger PCP, we could avoid to allocate from the zone. - In periodic vmstat updating kworker (via refresh_cpu_vm_stats()), decrease PCP high to try to free possible idle PCP pages. - When page reclaiming is active for the zone, stop increasing PCP high in allocating path, decrease PCP high and free some pages in freeing path. So, the PCP high can be tuned to the page allocating/freeing depth of workloads eventually. One issue of the algorithm is that if the number of pages allocated is much more than that of pages freed on a CPU, the PCP high may become the maximal value even if the allocating/freeing depth is small. But this isn't a severe issue, because there are no idle pages in this case. One alternative choice is to increase PCP high when we drain PCP via trying to free pages to the zone, but don't increase PCP high during PCP refilling. This can avoid the issue above. But if the number of pages allocated is much less than that of pages freed on a CPU, there will be many idle pages in PCP and it is hard to free these idle pages. 1/8 (>> 3) of PCP high will be decreased periodically. The value 1/8 is kind of arbitrary. Just to make sure that the idle PCP pages will be freed eventually. On a 2-socket Intel server with 224 logical CPU, we run 8 kbuild instances in parallel (each with `make -j 28`) in 8 cgroup. This simulates the kbuild server that is used by 0-Day kbuild service. With the patch, the build time decreases 3.5%. The cycles% of the spinlock contention (mostly for zone lock) decreases from 11.0% to 0.5%. The number of PCP draining for high order pages freeing (free_high) decreases 65.6%. The number of pages allocated from zone (instead of from PCP) decreases 83.9%. Link: https://lkml.kernel.org/r/20231016053002.756205-8-ying.huang@intel.comSigned-off-by:
Mel Gorman <mgorman@techsingularity.net> Suggested-by:
Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <jweiner@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Lameter <cl@linux.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by:
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