- 25 May, 2010 40 commits
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Mathieu Desnoyers authored
asm-generic/atomic.h has been derived from the mn10300 implementation. Remove the now duplicated mn10300 implementation by including the generic version instead. This adds cmpxchg_local() and cmpxchg64_local() for free to the architecture, as they are implemented in asm-generic/atomic.h. Signed-off-by:
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by:
David Howells <dhowells@redhat.com> Acked-by:
Peter Fritzsche <peter.fritzsche@gmx.de> Acked-by:
Arnd Bergmann <arnd@arndb.de> Cc: Jamie Lokier <jamie@shareable.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Keith M Wesolowski <wesolows@foobazco.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Greg Ungerer authored
Commit 8b505ca8 ("serial: 68328serial.c: remove BAUD_TABLE_SIZE macro") misses one use of BAUD_TABLE_SIZE. So the resulting 68328serial.c does not compile: drivers/serial/68328serial.c: In function `m68328_console_setup': drivers/serial/68328serial.c:1439: error: `BAUD_TABLE_SIZE' undeclared (first use in this function) drivers/serial/68328serial.c:1439: error: (Each undeclared identifier is reported only once drivers/serial/68328serial.c:1439: error: for each function it appears in.) Fix that last use of it. Signed-off-by:
Greg Ungerer <gerg@uclinux.org> Cc: Thiago Farina <tfransosi@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: <stable@kernel.org> Signed-off-by:
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FUJITA Tomonori authored
Architectures that handle DMA-non-coherent memory need to set ARCH_KMALLOC_MINALIGN to make sure that kmalloc'ed buffer is DMA-safe: the buffer doesn't share a cache with the others. Signed-off-by:
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Acked-by:
Pekka Enberg <penberg@cs.helsinki.fi> Cc: <stable@kernel.org> Signed-off-by:
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David Howells authored
Extend gdbstub to support more features of gdb remote protocol to keep gdb-7 and emacs gud mode happy: (*) The D command. Detach debugger. (*) The H command. Handle setting the target thread by ignoring it. (*) The qAttached command. Indicate we 'attached' to an existing process. (*) The qC command. Indicate that the current thread ID is 0. (*) The qOffsets command. Indicate that no relocation has been done. (*) The qSymbol:: command. Indicate that we're not interested in looking up any symbol addresses. (*) The qSupported command. Indicate the maximum packet size and the fact that reverse step and continue aren't supported. (*) The vCont? command. Indicate that we don't support any of its variants. Also make it possible to trace the commands and replies without tracing the individual character I/O. [akpm@linux-foundation.org: make gdbstub_handle_query() static] Signed-off-by: -
Chris Metcalf authored
This ensures that platforms with lowmem PAs above 32 bits work correctly by avoiding truncating the PA during a left shift. Signed-off-by:
Chris Metcalf <cmetcalf@tilera.com> Cc: Barry Song <21cnbao@gmail.com> Signed-off-by:
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Haicheng Li authored
Add global mutex zonelists_mutex to fix the possible race: CPU0 CPU1 CPU2 (1) zone->present_pages += online_pages; (2) build_all_zonelists(); (3) alloc_page(); (4) free_page(); (5) build_all_zonelists(); (6) __build_all_zonelists(); (7) zone->pageset = alloc_percpu(); In step (3,4), zone->pageset still points to boot_pageset, so bad things may happen if 2+ nodes are in this state. Even if only 1 node is accessing the boot_pageset, (3) may still consume too much memory to fail the memory allocations in step (7). Besides, atomic operation ensures alloc_percpu() in step (7) will never fail since there is a new fresh memory block added in step(6). [haicheng.li@linux.intel.com: hold zonelists_mutex when build_all_zonelists] Signed-off-by:Haicheng Li <haicheng.li@linux.intel.com> Signed-off-by:
Wu Fengguang <fengguang.wu@intel.com> Reviewed-by:
Andi Kleen <andi.kleen@intel.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Tejun Heo <tj@kernel.org> Signed-off-by:
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Haicheng Li authored
For each new populated zone of hotadded node, need to update its pagesets with dynamically allocated per_cpu_pageset struct for all possible CPUs: 1) Detach zone->pageset from the shared boot_pageset at end of __build_all_zonelists(). 2) Use mutex to protect zone->pageset when it's still shared in onlined_pages() Otherwises, multiple zones of different nodes would share same boot strapping boot_pageset for same CPU, which will finally cause below kernel panic: ------------[ cut here ]------------ kernel BUG at mm/page_alloc.c:1239! invalid opcode: 0000 [#1] SMP ... Call Trace: [<ffffffff811300c1>] __alloc_pages_nodemask+0x131/0x7b0 [<ffffffff81162e67>] alloc_pages_current+0x87/0xd0 [<ffffffff81128407>] __page_cache_alloc+0x67/0x70 [<ffffffff811325f0>] __do_page_cache_readahead+0x120/0x260 [<ffffffff81132751>] ra_submit+0x21/0x30 [<ffffffff811329c6>] ondemand_readahead+0x166/0x2c0 [<ffffffff81132ba0>] page_cache_async_readahead+0x80/0xa0 [<ffffffff8112a0e4>] generic_file_aio_read+0x364/0x670 [<ffffffff81266cfa>] nfs_file_read+0xca/0x130 [<ffffffff8117b20a>] do_sync_read+0xfa/0x140 [<ffffffff8117bf75>] vfs_read+0xb5/0x1a0 [<ffffffff8117c151>] sys_read+0x51/0x80 [<ffffffff8103c032>] system_call_fastpath+0x16/0x1b RIP [<ffffffff8112ff13>] get_page_from_freelist+0x883/0x900 RSP <ffff88000d1e78a8> ---[ end trace 4bda28328b9990db ] [akpm@linux-foundation.org: merge fix] Signed-off-by:Christoph Lameter <cl@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Tejun Heo <tj@kernel.org> Signed-off-by:
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Wu Fengguang authored
No behavior change here. Move some of setup_per_cpu_pageset() code into a new function setup_zone_pageset() that will be useful for memory hotplug. Signed-off-by:
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Marcelo Roberto Jimenez authored
Got this while compiling for ARM/SA1100: mm/sparse.c: In function '__section_nr': mm/sparse.c:135: warning: 'root' is used uninitialized in this function This patch follows Russell King's suggestion for a new calculation for NR_SECTION_ROOTS. Thanks also to Sergei Shtylyov for pointing out the existence of the macro DIV_ROUND_UP. Atsushi Nemoto observed: : This fix doesn't just silence the warning - it fixes a real problem. : : Without this fix, mem_section[] might have 0 size so mem_section[0] : will share other variable area. For example, I got: : : c030c700 b __warned.16478 : c030c700 B mem_section : c030c701 b __warned.16483 : : This might cause very strange behavior. Your patch actually fixes it. Signed-off-by:
Marcelo Roberto Jimenez <mroberto@cpti.cetuc.puc-rio.br> Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Sergei Shtylyov <sshtylyov@mvista.com> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by:
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Akinobu Mita authored
In f4112de6 ("mm: introduce debug_kmap_atomic") I said that debug_kmap_atomic() needs CONFIG_TRACE_IRQFLAGS_SUPPORT. It was wrong. (I thought irqs_disabled() is only available when the architecture has CONFIG_TRACE_IRQFLAGS_SUPPORT) Remove the #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT check to enable kmap_atomic() debugging for the architectures which do not have CONFIG_TRACE_IRQFLAGS_SUPPORT. Reported-by:
Akinobu Mita <akinobu.mita@gmail.com> Signed-off-by:
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matt mooney authored
Add parenthesis in a define. This doesn't change functionality. checkpatch errors: 1) white space fixes 2) add spaces after comas Signed-off-by:
matt mooney <mfm@muteddisk.com> Cc: Dan Carpenter <error27@gmail.com> Signed-off-by:
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matt mooney authored
Fix minor spelling errors in a few comments; no code changes. Signed-off-by:
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minskey guo authored
Enable users to online CPUs even if the CPUs belongs to a numa node which doesn't have onlined local memory. The zonlists(pg_data_t.node_zonelists[]) of a numa node are created either in system boot/init period, or at the time of local memory online. For a numa node without onlined local memory, its zonelists are not initialized at present. As a result, any memory allocation operations executed by CPUs within this node will fail. In fact, an out-of-memory error is triggered when attempt to online CPUs before memory comes to online. This patch tries to create zonelists for such numa nodes, so that the memory allocation for this node can be fallback'ed to other nodes. [akpm@linux-foundation.org: remove unneeded export] [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: minskey guo<chaohong.guo@intel.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Yasunori Goto <y-goto@jp.fujitsu.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by:
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Johannes Weiner authored
For now, we have global isolation vs. memory control group isolation, do not allow the reclaim entry function to set an arbitrary page isolation callback, we do not need that flexibility. And since we already pass around the group descriptor for the memory control group isolation case, just use it to decide which one of the two isolator functions to use. The decisions can be merged into nearby branches, so no extra cost there. In fact, we save the indirect calls. Signed-off-by:
Johannes Weiner <hannes@cmpxchg.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:
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Johannes Weiner authored
This scan control is abused to communicate a return value from shrink_zones(). Write this idiomatically and remove the knob. Signed-off-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:
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Johannes Weiner authored
Signed-off-by:
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Richard Kennedy authored
When wb_writeback() hasn't written anything it will re-acquire the inode lock before calling inode_wait_for_writeback. This change tests the sync bit first so that is doesn't need to drop & re-acquire the lock if the inode became available while wb_writeback() was waiting to get the lock. Signed-off-by:
Richard Kennedy <richard@rsk.demon.co.uk> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by:
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KOSAKI Motohiro authored
free_hot_cold_page() and __free_pages_ok() have very similar freeing preparation. Consolidate them. [akpm@linux-foundation.org: fix busted coding style] Signed-off-by:
Mel Gorman <mel@csn.ul.ie> Signed-off-by:
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KOSAKI Motohiro authored
If vmscan is under lumpy reclaim mode, it have to ignore referenced bit for making contenious free pages. but current page_check_references() doesn't. Fix it. Signed-off-by:
Minchan Kim <minchan.kim@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Signed-off-by:
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Huang Shijie authored
Fix a wrong comment over page_cache_async_readahead(). Signed-off-by:
Huang Shijie <shijie8@gmail.com> Acked-by:
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Shaohua Li authored
get_scan_ratio() calculates percentage and if the percentage is < 1%, it will round percentage down to 0% and cause we completely ignore scanning anon/file pages to reclaim memory even the total anon/file pages are very big. To avoid underflow, we don't use percentage, instead we directly calculate how many pages should be scaned. In this way, we should get several scanned pages for < 1% percent. This has some benefits: 1. increase our calculation precision 2. making our scan more smoothly. Without this, if percent[x] is underflow, shrink_zone() doesn't scan any pages and suddenly it scans all pages when priority is zero. With this, even priority isn't zero, shrink_zone() gets chance to scan some pages. Note, this patch doesn't really change logics, but just increase precision. For system with a lot of memory, this might slightly changes behavior. For example, in a sequential file read workload, without the patch, we don't swap any anon pages. With it, if anon memory size is bigger than 16G, we will see one anon page swapped. The 16G is calculated as PAGE_SIZE * priority(4096) * (fp/ap). fp/ap is assumed to be 1024 which is common in this workload. So the impact sounds not a big deal. Signed-off-by:
Shaohua Li <shaohua.li@intel.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by:
Rik van Riel <riel@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by:
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Greg Thelen authored
Use mm->task_size instead of TASK_SIZE to ensure that the entire user address space is migrated. mm->task_size is independent of the calling task context. TASK SIZE may be dependant on the address space size of the calling process. Usage of TASK_SIZE can lead to partial address space migration if the calling process was 32 bit and the migrating process was 64 bit. Here is the test script used on 64 system with a 32 bit echo process: mount -t cgroup none /cgroup -o cpuset cd /cgroup mkdir 0 echo 1 > 0/cpuset.cpus echo 0 > 0/cpuset.mems echo 1 > 0/cpuset.memory_migrate mkdir 1 echo 1 > 1/cpuset.cpus echo 1 > 1/cpuset.mems echo 1 > 1/cpuset.memory_migrate echo $$ > 0/tasks 64_bit_process & pid=$! echo $pid > 1/tasks # This does not migrate all process pages without # this patch. If 64 bit echo is used or this patch is # applied, then the full address space of $pid is # migrated. To check memory migration, I watched: grep MemUsed /sys/devices/system/node/node*/meminfo Signed-off-by:Greg Thelen <gthelen@google.com> Acked-by:
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Mel Gorman authored
The fragmentation index may indicate that a failure is due to external fragmentation but after a compaction run completes, it is still possible for an allocation to fail. There are two obvious reasons as to why o Page migration cannot move all pages so fragmentation remains o A suitable page may exist but watermarks are not met In the event of compaction followed by an allocation failure, this patch defers further compaction in the zone (1 << compact_defer_shift) times. If the next compaction attempt also fails, compact_defer_shift is increased up to a maximum of 6. If compaction succeeds, the defer counters are reset again. The zone that is deferred is the first zone in the zonelist - i.e. the preferred zone. To defer compaction in the other zones, the information would need to be stored in the zonelist or implemented similar to the zonelist_cache. This would impact the fast-paths and is not justified at this time. Signed-off-by:
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Mel Gorman authored
mm: compaction: add a tunable that decides when memory should be compacted and when it should be reclaimed The kernel applies some heuristics when deciding if memory should be compacted or reclaimed to satisfy a high-order allocation. One of these is based on the fragmentation. If the index is below 500, memory will not be compacted. This choice is arbitrary and not based on data. To help optimise the system and set a sensible default for this value, this patch adds a sysctl extfrag_threshold. The kernel will only compact memory if the fragmentation index is above the extfrag_threshold. [randy.dunlap@oracle.com: Fix build errors when proc fs is not configured] Signed-off-by:
Randy Dunlap <randy.dunlap@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:
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Mel Gorman authored
Ordinarily when a high-order allocation fails, direct reclaim is entered to free pages to satisfy the allocation. With this patch, it is determined if an allocation failed due to external fragmentation instead of low memory and if so, the calling process will compact until a suitable page is freed. Compaction by moving pages in memory is considerably cheaper than paging out to disk and works where there are locked pages or no swap. If compaction fails to free a page of a suitable size, then reclaim will still occur. Direct compaction returns as soon as possible. As each block is compacted, it is checked if a suitable page has been freed and if so, it returns. [akpm@linux-foundation.org: Fix build errors] [aarcange@redhat.com: fix count_vm_event preempt in memory compaction direct reclaim] Signed-off-by:
Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
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Mel Gorman authored
Add a per-node sysfs file called compact. When the file is written to, each zone in that node is compacted. The intention that this would be used by something like a job scheduler in a batch system before a job starts so that the job can allocate the maximum number of hugepages without significant start-up cost. Signed-off-by:
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:
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Mel Gorman authored
Add a proc file /proc/sys/vm/compact_memory. When an arbitrary value is written to the file, all zones are compacted. The expected user of such a trigger is a job scheduler that prepares the system before the target application runs. Signed-off-by:
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Mel Gorman authored
This patch is the core of a mechanism which compacts memory in a zone by relocating movable pages towards the end of the zone. A single compaction run involves a migration scanner and a free scanner. Both scanners operate on pageblock-sized areas in the zone. The migration scanner starts at the bottom of the zone and searches for all movable pages within each area, isolating them onto a private list called migratelist. The free scanner starts at the top of the zone and searches for suitable areas and consumes the free pages within making them available for the migration scanner. The pages isolated for migration are then migrated to the newly isolated free pages. [aarcange@redhat.com: Fix unsafe optimisation] [mel@csn.ul.ie: do not schedule work on other CPUs for compaction] Signed-off-by:
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Mel Gorman authored
Currently, vmscan.c defines the isolation modes for __isolate_lru_page(). Memory compaction needs access to these modes for isolating pages for migration. This patch exports them. Signed-off-by:
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Mel Gorman authored
The fragmentation fragmentation index, is only meaningful if an allocation would fail and indicates what the failure is due to. A value of -1 such as in many of the examples above states that the allocation would succeed. If it would fail, the value is between 0 and 1. A value tending towards 0 implies the allocation failed due to a lack of memory. A value tending towards 1 implies it failed due to external fragmentation. For the most part, the huge page size will be the size of interest but not necessarily so it is exported on a per-order and per-zo basis via /sys/kernel/debug/extfrag/extfrag_index > cat /sys/kernel/debug/extfrag/extfrag_index Node 0, zone DMA -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.00 Node 0, zone Normal -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 0.954 Signed-off-by:
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Mel Gorman authored
The unusable free space index measures how much of the available free memory cannot be used to satisfy an allocation of a given size and is a value between 0 and 1. The higher the value, the more of free memory is unusable and by implication, the worse the external fragmentation is. For the most part, the huge page size will be the size of interest but not necessarily so it is exported on a per-order and per-zone basis via /sys/kernel/debug/extfrag/unusable_index. > cat /sys/kernel/debug/extfrag/unusable_index Node 0, zone DMA 0.000 0.000 0.000 0.001 0.005 0.013 0.021 0.037 0.037 0.101 0.230 Node 0, zone Normal 0.000 0.000 0.000 0.001 0.002 0.002 0.005 0.015 0.028 0.028 0.054 [akpm@linux-foundation.org: Fix allnoconfig] Signed-off-by:
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Mel Gorman authored
mm: migration: avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks Page migration requires rmap to be able to find all ptes mapping a page at all times, otherwise the migration entry can be instantiated, but it is possible to leave one behind if the second rmap_walk fails to find the page. If this page is later faulted, migration_entry_to_page() will call BUG because the page is locked indicating the page was migrated by the migration PTE not cleaned up. For example kernel BUG at include/linux/swapops.h:105! invalid opcode: 0000 [#1] PREEMPT SMP ... Call Trace: [<ffffffff810e951a>] handle_mm_fault+0x3f8/0x76a [<ffffffff8130c7a2>] do_page_fault+0x44a/0x46e [<ffffffff813099b5>] page_fault+0x25/0x30 [<ffffffff8114de33>] load_elf_binary+0x152a/0x192b [<ffffffff8111329b>] search_binary_handler+0x173/0x313 [<ffffffff81114896>] do_execve+0x219/0x30a [<ffffffff8100a5c6>] sys_execve+0x43/0x5e [<ffffffff8100320a>] stub_execve+0x6a/0xc0 RIP [<ffffffff811094ff>] migration_entry_wait+0xc1/0x129 There is a race between shift_arg_pages and migration that triggers this bug. A temporary stack is setup during exec and later moved. If migration moves a page in the temporary stack and the VMA is then removed before migration completes, the migration PTE may not be found leading to a BUG when the stack is faulted. This patch causes pages within the temporary stack during exec to be skipped by migration. It does this by marking the VMA covering the temporary stack with an otherwise impossible combination of VMA flags. These flags are cleared when the temporary stack is moved to its final location. [kamezawa.hiroyu@jp.fujitsu.com: idea for having migration skip temporary stacks] Signed-off-by:
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Mel Gorman authored
CONFIG_MIGRATION currently depends on CONFIG_NUMA or on the architecture being able to hot-remove memory. The main users of page migration such as sys_move_pages(), sys_migrate_pages() and cpuset process migration are only beneficial on NUMA so it makes sense. As memory compaction will operate within a zone and is useful on both NUMA and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the user selects CONFIG_COMPACTION as an option. [akpm@linux-foundation.org: Depend on CONFIG_HUGETLB_PAGE] Signed-off-by:
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Mel Gorman authored
PageAnon pages that are unmapped may or may not have an anon_vma so are not currently migrated. However, a swap cache page can be migrated and fits this description. This patch identifies page swap caches and allows them to be migrated but ensures that no attempt to made to remap the pages would would potentially try to access an already freed anon_vma. Signed-off-by:
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Mel Gorman authored
rmap_walk_anon() was triggering errors in memory compaction that look like use-after-free errors. The problem is that between the page being isolated from the LRU and rcu_read_lock() being taken, the mapcount of the page dropped to 0 and the anon_vma gets freed. This can happen during memory compaction if pages being migrated belong to a process that exits before migration completes. Hence, the use-after-free race looks like 1. Page isolated for migration 2. Process exits 3. page_mapcount(page) drops to zero so anon_vma was no longer reliable 4. unmap_and_move() takes the rcu_lock but the anon_vma is already garbage 4. call try_to_unmap, looks up tha anon_vma and "locks" it but the lock is garbage. This patch checks the mapcount after the rcu lock is taken. If the mapcount is zero, the anon_vma is assumed to be freed and no further action is taken. Signed-off-by: -
Mel Gorman authored
For clarity of review, KSM and page migration have separate refcounts on the anon_vma. While clear, this is a waste of memory. This patch gets KSM and page migration to share their toys in a spirit of harmony. Signed-off-by:
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Mel Gorman authored
This patchset is a memory compaction mechanism that reduces external fragmentation memory by moving GFP_MOVABLE pages to a fewer number of pageblocks. The term "compaction" was chosen as there are is a number of mechanisms that are not mutually exclusive that can be used to defragment memory. For example, lumpy reclaim is a form of defragmentation as was slub "defragmentation" (really a form of targeted reclaim). Hence, this is called "compaction" to distinguish it from other forms of defragmentation. In this implementation, a full compaction run involves two scanners operating within a zone - a migration and a free scanner. The migration scanner starts at the beginning of a zone and finds all movable pages within one pageblock_nr_pages-sized area and isolates them on a migratepages list. The free scanner begins at the end of the zone and searches on a per-area basis for enough free pages to migrate all the pages on the migratepages list. As each area is respectively migrated or exhausted of free pages, the scanners are advanced one area. A compaction run completes within a zone when the two scanners meet. This method is a bit primitive but is easy to understand and greater sophistication would require maintenance of counters on a per-pageblock basis. This would have a big impact on allocator fast-paths to improve compaction which is a poor trade-off. It also does not try relocate virtually contiguous pages to be physically contiguous. However, assuming transparent hugepages were in use, a hypothetical khugepaged might reuse compaction code to isolate free pages, split them and relocate userspace pages for promotion. Memory compaction can be triggered in one of three ways. It may be triggered explicitly by writing any value to /proc/sys/vm/compact_memory and compacting all of memory. It can be triggered on a per-node basis by writing any value to /sys/devices/system/node/nodeN/compact where N is the node ID to be compacted. When a process fails to allocate a high-order page, it may compact memory in an attempt to satisfy the allocation instead of entering direct reclaim. Explicit compaction does not finish until the two scanners meet and direct compaction ends if a suitable page becomes available that would meet watermarks. The series is in 14 patches. The first three are not "core" to the series but are important pre-requisites. Patch 1 reference counts anon_vma for rmap_walk_anon(). Without this patch, it's possible to use anon_vma after free if the caller is not holding a VMA or mmap_sem for the pages in question. While there should be no existing user that causes this problem, it's a requirement for memory compaction to be stable. The patch is at the start of the series for bisection reasons. Patch 2 merges the KSM and migrate counts. It could be merged with patch 1 but would be slightly harder to review. Patch 3 skips over unmapped anon pages during migration as there are no guarantees about the anon_vma existing. There is a window between when a page was isolated and migration started during which anon_vma could disappear. Patch 4 notes that PageSwapCache pages can still be migrated even if they are unmapped. Patch 5 allows CONFIG_MIGRATION to be set without CONFIG_NUMA Patch 6 exports a "unusable free space index" via debugfs. It's a measure of external fragmentation that takes the size of the allocation request into account. It can also be calculated from userspace so can be dropped if requested Patch 7 exports a "fragmentation index" which only has meaning when an allocation request fails. It determines if an allocation failure would be due to a lack of memory or external fragmentation. Patch 8 moves the definition for LRU isolation modes for use by compaction Patch 9 is the compaction mechanism although it's unreachable at this point Patch 10 adds a means of compacting all of memory with a proc trgger Patch 11 adds a means of compacting a specific node with a sysfs trigger Patch 12 adds "direct compaction" before "direct reclaim" if it is determined there is a good chance of success. Patch 13 adds a sysctl that allows tuning of the threshold at which the kernel will compact or direct reclaim Patch 14 temporarily disables compaction if an allocation failure occurs after compaction. Testing of compaction was in three stages. For the test, debugging, preempt, the sleep watchdog and lockdep were all enabled but nothing nasty popped out. min_free_kbytes was tuned as recommended by hugeadm to help fragmentation avoidance and high-order allocations. It was tested on X86, X86-64 and PPC64. Ths first test represents one of the easiest cases that can be faced for lumpy reclaim or memory compaction. 1. Machine freshly booted and configured for hugepage usage with a) hugeadm --create-global-mounts b) hugeadm --pool-pages-max DEFAULT:8G c) hugeadm --set-recommended-min_free_kbytes d) hugeadm --set-recommended-shmmax The min_free_kbytes here is important. Anti-fragmentation works best when pageblocks don't mix. hugeadm knows how to calculate a value that will significantly reduce the worst of external-fragmentation-related events as reported by the mm_page_alloc_extfrag tracepoint. 2. Load up memory a) Start updatedb b) Create in parallel a X files of pagesize*128 in size. Wait until files are created. By parallel, I mean that 4096 instances of dd were launched, one after the other using &. The crude objective being to mix filesystem metadata allocations with the buffer cache. c) Delete every second file so that pageblocks are likely to have holes d) kill updatedb if it's still running At this point, the system is quiet, memory is full but it's full with clean filesystem metadata and clean buffer cache that is unmapped. This is readily migrated or discarded so you'd expect lumpy reclaim to have no significant advantage over compaction but this is at the POC stage. 3. In increments, attempt to allocate 5% of memory as hugepages. Measure how long it took, how successful it was, how many direct reclaims took place and how how many compactions. Note the compaction figures might not fully add up as compactions can take place for orders other than the hugepage size X86 vanilla compaction Final page count 913 916 (attempted 1002) pages reclaimed 68296 9791 X86-64 vanilla compaction Final page count: 901 902 (attempted 1002) Total pages reclaimed: 112599 53234 PPC64 vanilla compaction Final page count: 93 94 (attempted 110) Total pages reclaimed: 103216 61838 There was not a dramatic improvement in success rates but it wouldn't be expected in this case either. What was important is that fewer pages were reclaimed in all cases reducing the amount of IO required to satisfy a huge page allocation. The second tests were all performance related - kernbench, netperf, iozone and sysbench. None showed anything too remarkable. The last test was a high-order allocation stress test. Many kernel compiles are started to fill memory with a pressured mix of unmovable and movable allocations. During this, an attempt is made to allocate 90% of memory as huge pages - one at a time with small delays between attempts to avoid flooding the IO queue. vanilla compaction Percentage of request allocated X86 98 99 Percentage of request allocated X86-64 95 98 Percentage of request allocated PPC64 55 70 This patch: rmap_walk_anon() does not use page_lock_anon_vma() for looking up and locking an anon_vma and it does not appear to have sufficient locking to ensure the anon_vma does not disappear from under it. This patch copies an approach used by KSM to take a reference on the anon_vma while pages are being migrated. This should prevent rmap_walk() running into nasty surprises later because anon_vma has been freed. Signed-off-by: -
David Rientjes authored
There are two types of zonelist ordering methodologies: - node order, preferring allocations on a node to stay local to and - zone order, preferring allocations come from a higher zone to avoid allocating in lowmem zones even though they may not be local. The ordering technique used by the kernel is configurable on the command line, but also has some logic to determine what the default should be. This logic currently lacks knowledge of systems where a node may only have lowmem. For such systems, it is necessary to use node order so that GFP_KERNEL allocations may be satisfied by nodes consisting of only lowmem. If zone order is used, GFP_KERNEL allocations to such nodes are actually allocated on a node with local affinity that includes ZONE_NORMAL. This change defaults to node zonelist ordering if any node lacks ZONE_NORMAL. To force zone order, append 'numa_zonelist_order=zone' to the kernel command line. Signed-off-by:
David Rientjes <rientjes@google.com> Acked-by:
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Naoya Horiguchi authored
If !CONFIG_HUGETLB_PAGE, pagemap_hugetlb_range() is never called. So put it (and its calling function) into #ifdef block. Signed-off-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Acked-by:
Matt Mackall <mpm@selenic.com> Signed-off-by:
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Johannes Weiner authored
Do page table walks with the well-known nested loops we use in several other places already. This avoids doing full page table walks after every pte range and also allows to handle unmapped areas bigger than one pte range in one go. Signed-off-by:
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