- 12 Feb, 2015 40 commits
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Kirill A. Shutemov authored
Currently pagewalker splits all THP pages on any clear_refs request. It's not necessary. We can handle this on PMD level. One side effect is that soft dirty will potentially see more dirty memory, since we will mark whole THP page dirty at once. Sanity checked with CRIU test suite. More testing is required. Signed-off-by:
Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by:
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by:
Cyrill Gorcunov <gorcunov@openvz.org> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Naoya Horiguchi authored
walk_page_range() silently skips vma having VM_PFNMAP set, which leads to undesirable behaviour at client end (who called walk_page_range). For example for pagemap_read(), when no callbacks are called against VM_PFNMAP vma, pagemap_read() may prepare pagemap data for next virtual address range at wrong index. That could confuse and/or break userspace applications. This patch avoid this misbehavior caused by vma(VM_PFNMAP) like follows: - for pagemap_read() which has its own ->pte_hole(), call the ->pte_hole() over vma(VM_PFNMAP), - for clear_refs and queue_pages which have their own ->tests_walk, just return 1 and skip vma(VM_PFNMAP). This is no problem because these are not interested in hole regions, - for other callers, just skip the vma(VM_PFNMAP) as a default behavior. Signed-off-by:
Shiraz Hashim <shashim@codeaurora.org> Signed-off-by:
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Naoya Horiguchi authored
queue_pages_range() does page table walking in its own way now, but there is some code duplicate. This patch applies page table walker to reduce lines of code. queue_pages_range() has to do some precheck to determine whether we really walk over the vma or just skip it. Now we have test_walk() callback in mm_walk for this purpose, so we can do this replacement cleanly. queue_pages_test_walk() depends on not only the current vma but also the previous one, so queue_pages->prev is introduced to remember it. Signed-off-by:
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Naoya Horiguchi authored
We don't have to use mm_walk->private to pass vma to the callback function because of mm_walk->vma. And walk_page_vma() is useful if we walk over a single vma. Signed-off-by:
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Naoya Horiguchi authored
pagewalk.c can handle vma in itself, so we don't have to pass vma via walk->private. And both of mem_cgroup_count_precharge() and mem_cgroup_move_charge() do for each vma loop themselves, but now it's done in pagewalk.c, so let's clean up them. Signed-off-by:
Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by:
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Naoya Horiguchi authored
pagewalk.c can handle vma in itself, so we don't have to pass vma via walk->private. And show_numa_map() walks pages on vma basis, so using walk_page_vma() is preferable. Signed-off-by:
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Naoya Horiguchi authored
Just doing s/gather_hugetbl_stats/gather_hugetlb_stats/g, this makes code grep-friendly. Signed-off-by:
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Naoya Horiguchi authored
Page table walker has the information of the current vma in mm_walk, so we don't have to call find_vma() in each pagemap_(pte|hugetlb)_range() call any longer. Currently pagemap_pte_range() does vma loop itself, so this patch reduces many lines of code. NULL-vma check is omitted because we assume that we never run these callbacks on any address outside vma. And even if it were broken, NULL pointer dereference would be detected, so we can get enough information for debugging. Signed-off-by:
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Naoya Horiguchi authored
clear_refs_write() has some prechecks to determine if we really walk over a given vma. Now we have a test_walk() callback to filter vmas, so let's utilize it. Signed-off-by:
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Naoya Horiguchi authored
pagewalk.c can handle vma in itself, so we don't have to pass vma via walk->private. And show_smap() walks pages on vma basis, so using walk_page_vma() is preferable. Signed-off-by:
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Naoya Horiguchi authored
Introduce walk_page_vma(), which is useful for the callers which want to walk over a given vma. It's used by later patches. Signed-off-by:
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Naoya Horiguchi authored
Current implementation of page table walker has a fundamental problem in vma handling, which started when we tried to handle vma(VM_HUGETLB). Because it's done in pgd loop, considering vma boundary makes code complicated and bug-prone. From the users viewpoint, some user checks some vma-related condition to determine whether the user really does page walk over the vma. In order to solve these, this patch moves vma check outside pgd loop and introduce a new callback ->test_walk(). Signed-off-by:
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Naoya Horiguchi authored
Currently no user of page table walker sets ->pgd_entry() or ->pud_entry(), so checking their existence in each loop is just wasting CPU cycle. So let's remove it to reduce overhead. Signed-off-by:
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Konstantin Khlebnikov authored
Lockless access to pte in pagemap_pte_range() might race with page migration and trigger BUG_ON(!PageLocked()) in migration_entry_to_page(): CPU A (pagemap) CPU B (migration) lock_page() try_to_unmap(page, TTU_MIGRATION...) make_migration_entry() set_pte_at() <read *pte> pte_to_pagemap_entry() remove_migration_ptes() unlock_page() if(is_migration_entry()) migration_entry_to_page() BUG_ON(!PageLocked(page)) Also lockless read might be non-atomic if pte is larger than wordsize. Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes. Fixes: 052fb0d6 ("proc: report file/anon bit in /proc/pid/pagemap") Signed-off-by:Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reported-by:
Andrey Ryabinin <a.ryabinin@samsung.com> Reviewed-by:
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Andrea Arcangeli authored
Use the more generic get_user_pages_unlocked which has the additional benefit of passing FAULT_FLAG_ALLOW_RETRY at the very first page fault (which allows the first page fault in an unmapped area to be always able to block indefinitely by being allowed to release the mmap_sem). Signed-off-by:
Andrea Arcangeli <aarcange@redhat.com> Reviewed-by:
Andres Lagar-Cavilla <andreslc@google.com> Reviewed-by:
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Andrea Arcangeli authored
This allows those get_user_pages calls to pass FAULT_FLAG_ALLOW_RETRY to the page fault in order to release the mmap_sem during the I/O. Signed-off-by:
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Andrea Arcangeli authored
This allows the get_user_pages_fast slow path to release the mmap_sem before blocking. Signed-off-by:
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Andrea Arcangeli authored
Some callers (like KVM) may want to set the gup_flags like FOLL_HWPOSION to get a proper -EHWPOSION retval instead of -EFAULT to take a more appropriate action if get_user_pages runs into a memory failure. Signed-off-by:
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Andrea Arcangeli authored
FAULT_FOLL_ALLOW_RETRY allows the page fault to drop the mmap_sem for reading to reduce the mmap_sem contention (for writing), like while waiting for I/O completion. The problem is that right now practically no get_user_pages call uses FAULT_FOLL_ALLOW_RETRY, so we're not leveraging that nifty feature. Andres fixed it for the KVM page fault. However get_user_pages_fast remains uncovered, and 99% of other get_user_pages aren't using it either (the only exception being FOLL_NOWAIT in KVM which is really nonblocking and in fact it doesn't even release the mmap_sem). So this patchsets extends the optimization Andres did in the KVM page fault to the whole kernel. It makes most important places (including gup_fast) to use FAULT_FOLL_ALLOW_RETRY to reduce the mmap_sem hold times during I/O. The only few places that remains uncovered are drivers like v4l and other exceptions that tends to work on their own memory and they're not working on random user memory (for example like O_DIRECT that uses gup_fast and is fully covered by this patch). A follow up patch should probably also add a printk_once warning to get_user_pages that should go obsolete and be phased out eventually. The "vmas" parameter of get_user_pages makes it fundamentally incompatible with FAULT_FOLL_ALLOW_RETRY (vmas array becomes meaningless the moment the mmap_sem is released). While this is just an optimization, this becomes an absolute requirement for the userfaultfd feature http://lwn.net/Articles/615086/ . The userfaultfd allows to block the page fault, and in order to do so I need to drop the mmap_sem first. So this patch also ensures that all memory where userfaultfd could be registered by KVM, the very first fault (no matter if it is a regular page fault, or a get_user_pages) always has FAULT_FOLL_ALLOW_RETRY set. Then the userfaultfd blocks and it is waken only when the pagetable is already mapped. The second fault attempt after the wakeup doesn't need FAULT_FOLL_ALLOW_RETRY, so it's ok to retry without it. This patch (of 5): We can leverage the VM_FAULT_RETRY functionality in the page fault paths better by using either get_user_pages_locked or get_user_pages_unlocked. The former allows conversion of get_user_pages invocations that will have to pass a "&locked" parameter to know if the mmap_sem was dropped during the call. Example from: down_read(&mm->mmap_sem); do_something() get_user_pages(tsk, mm, ..., pages, NULL); up_read(&mm->mmap_sem); to: int locked = 1; down_read(&mm->mmap_sem); do_something() get_user_pages_locked(tsk, mm, ..., pages, &locked); if (locked) up_read(&mm->mmap_sem); The latter is suitable only as a drop in replacement of the form: down_read(&mm->mmap_sem); get_user_pages(tsk, mm, ..., pages, NULL); up_read(&mm->mmap_sem); into: get_user_pages_unlocked(tsk, mm, ..., pages); Where tsk, mm, the intermediate "..." paramters and "pages" can be any value as before. Just the last parameter of get_user_pages (vmas) must be NULL for get_user_pages_locked|unlocked to be usable (the latter original form wouldn't have been safe anyway if vmas wasn't null, for the former we just make it explicit by dropping the parameter). If vmas is not NULL these two methods cannot be used. Signed-off-by:
Peter Feiner <pfeiner@google.com> Reviewed-by:
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Vlastimil Babka authored
The previous commit ("mm/thp: Allocate transparent hugepages on local node") introduced alloc_hugepage_vma() to mm/mempolicy.c to perform a special policy for THP allocations. The function has the same interface as alloc_pages_vma(), shares a lot of boilerplate code and a long comment. This patch merges the hugepage special case into alloc_pages_vma. The extra if condition should be cheap enough price to pay. We also prevent a (however unlikely) race with parallel mems_allowed update, which could make hugepage allocation restart only within the fallback call to alloc_hugepage_vma() and not reconsider the special rule in alloc_hugepage_vma(). Also by making sure mpol_cond_put(pol) is always called before actual allocation attempt, we can use a single exit path within the function. Also update the comment for missing node parameter and obsolete reference to mm_sem. Signed-off-by:Vlastimil Babka <vbabka@suse.cz> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
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Aneesh Kumar K.V authored
This make sure that we try to allocate hugepages from local node if allowed by mempolicy. If we can't, we fallback to small page allocation based on mempolicy. This is based on the observation that allocating pages on local node is more beneficial than allocating hugepages on remote node. With this patch applied we may find transparent huge page allocation failures if the current node doesn't have enough freee hugepages. Before this patch such failures result in us retrying the allocation on other nodes in the numa node mask. [akpm@linux-foundation.org: fix comment, add CONFIG_TRANSPARENT_HUGEPAGE dependency] Signed-off-by:
Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by:
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Joonsoo Kim authored
Compaction deferring logic is heavy hammer that block the way to the compaction. It doesn't consider overall system state, so it could prevent user from doing compaction falsely. In other words, even if system has enough range of memory to compact, compaction would be skipped due to compaction deferring logic. This patch add new tracepoint to understand work of deferring logic. This will also help to check compaction success and fail. Signed-off-by:
Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: David Rientjes <rientjes@google.com> Signed-off-by:
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Joonsoo Kim authored
It is not well analyzed that when/why compaction start/finish or not. With these new tracepoints, we can know much more about start/finish reason of compaction. I can find following bug with these tracepoint. http://www.spinics.net/lists/linux-mm/msg81582.htmlSigned-off-by:
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Joonsoo Kim authored
It'd be useful to know current range where compaction work for detailed analysis. With it, we can know pageblock where we actually scan and isolate, and, how much pages we try in that pageblock and can guess why it doesn't become freepage with pageblock order roughly. Signed-off-by:
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Joonsoo Kim authored
We now have tracepoint for begin event of compaction and it prints start position of both scanners, but, tracepoint for end event of compaction doesn't print finish position of both scanners. It'd be also useful to know finish position of both scanners so this patch add it. It will help to find odd behavior or problem on compaction internal logic. And mode is added to both begin/end tracepoint output, since according to mode, compaction behavior is quite different. And lastly, status format is changed to string rather than status number for readability. [akpm@linux-foundation.org: fix sparse warning] Signed-off-by:
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Joonsoo Kim authored
To check the range that compaction is working, tracepoint print start/end pfn of zone and start pfn of both scanner with decimal format. Since we manage all pages in order of 2 and it is well represented by hexadecimal, this patch change the tracepoint format from decimal to hexadecimal. This would improve readability. For example, it makes us easily notice whether current scanner try to compact previously attempted pageblock or not. Signed-off-by:
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Konstantin Khebnikov authored
Helper account_page_redirty() fixes dirty pages counter for redirtied pages. This patch puts it after dirtying and prevents temporary underflows of dirtied pages counters on zone/bdi and current->nr_dirtied. Signed-off-by:
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Kirill A. Shutemov authored
The problem is that we check nr_ptes/nr_pmds in exit_mmap() which happens *before* pgd_free(). And if an arch does pte/pmd allocation in pgd_alloc() and frees them in pgd_free() we see offset in counters by the time of the checks. We tried to workaround this by offsetting expected counter value according to FIRST_USER_ADDRESS for both nr_pte and nr_pmd in exit_mmap(). But it doesn't work in some cases: 1. ARM with LPAE enabled also has non-zero USER_PGTABLES_CEILING, but upper addresses occupied with huge pmd entries, so the trick with offsetting expected counter value will get really ugly: we will have to apply it nr_pmds, but not nr_ptes. 2. Metag has non-zero FIRST_USER_ADDRESS, but doesn't do allocation pte/pmd page tables allocation in pgd_alloc(), just setup a pgd entry which is allocated at boot and shared accross all processes. The proposal is to move the check to check_mm() which happens *after* pgd_free() and do proper accounting during pgd_alloc() and pgd_free() which would bring counters to zero if nothing leaked. Signed-off-by:
Tyler Baker <tyler.baker@linaro.org> Tested-by:
Nishanth Menon <nm@ti.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: James Hogan <james.hogan@imgtec.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Signed-off-by:
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Kirill A. Shutemov authored
Dave noticed that unprivileged process can allocate significant amount of memory -- >500 MiB on x86_64 -- and stay unnoticed by oom-killer and memory cgroup. The trick is to allocate a lot of PMD page tables. Linux kernel doesn't account PMD tables to the process, only PTE. The use-cases below use few tricks to allocate a lot of PMD page tables while keeping VmRSS and VmPTE low. oom_score for the process will be 0. #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> #include <sys/prctl.h> #define PUD_SIZE (1UL << 30) #define PMD_SIZE (1UL << 21) #define NR_PUD 130000 int main(void) { char *addr = NULL; unsigned long i; prctl(PR_SET_THP_DISABLE); for (i = 0; i < NR_PUD ; i++) { addr = mmap(addr + PUD_SIZE, PUD_SIZE, PROT_WRITE|PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); if (addr == MAP_FAILED) { perror("mmap"); break; } *addr = 'x'; munmap(addr, PMD_SIZE); mmap(addr, PMD_SIZE, PROT_WRITE|PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE|MAP_FIXED, -1, 0); if (addr == MAP_FAILED) perror("re-mmap"), exit(1); } printf("PID %d consumed %lu KiB in PMD page tables\n", getpid(), i * 4096 >> 10); return pause(); } The patch addresses the issue by account PMD tables to the process the same way we account PTE. The main place where PMD tables is accounted is __pmd_alloc() and free_pmd_range(). But there're few corner cases: - HugeTLB can share PMD page tables. The patch handles by accounting the table to all processes who share it. - x86 PAE pre-allocates few PMD tables on fork. - Architectures with FIRST_USER_ADDRESS > 0. We need to adjust sanity check on exit(2). Accounting only happens on configuration where PMD page table's level is present (PMD is not folded). As with nr_ptes we use per-mm counter. The counter value is used to calculate baseline for badness score by oom-killer. Signed-off-by:Dave Hansen <dave.hansen@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Reviewed-by:
Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by:
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Kirill A. Shutemov authored
ARM uses custom implementation of PMD folding in 2-level page table case. Generic code expects to see __PAGETABLE_PMD_FOLDED to be defined if PMD is folded, but ARM doesn't do this. Let's fix it. Defining __PAGETABLE_PMD_FOLDED will drop out unused __pmd_alloc(). It also fixes problems with recently-introduced pmd accounting on ARM without LPAE. Signed-off-by:
Simon Horman <horms@verge.net.au> Tested-by:
Simon Horman <horms+renesas@verge.net.au> Tested-by:
Fabio Estevam <festevam@gmail.com> Tested-by:
Felipe Balbi <balbi@ti.com> Tested-by:
Peter Ujfalusi <peter.ujfalusi@ti.com> Tested-by:
Krzysztof Kozlowski <k.kozlowski@samsung.com> Tested-by:
Geert Uytterhoeven <geert+renesas@glider.be> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: David Rientjes <rientjes@google.com> Cc: Russell King <linux@arm.linux.org.uk> Signed-off-by:
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Kirill A. Shutemov authored
If an architecure uses <asm-generic/4level-fixup.h>, build fails if we try to use PUD_SHIFT in generic code: In file included from arch/microblaze/include/asm/bug.h:1:0, from include/linux/bug.h:4, from include/linux/thread_info.h:11, from include/asm-generic/preempt.h:4, from arch/microblaze/include/generated/asm/preempt.h:1, from include/linux/preempt.h:18, from include/linux/spinlock.h:50, from include/linux/mmzone.h:7, from include/linux/gfp.h:5, from include/linux/slab.h:14, from mm/mmap.c:12: mm/mmap.c: In function 'exit_mmap': >> mm/mmap.c:2858:46: error: 'PUD_SHIFT' undeclared (first use in this function) round_up(FIRST_USER_ADDRESS, PUD_SIZE) >> PUD_SHIFT); ^ include/asm-generic/bug.h:86:25: note: in definition of macro 'WARN_ON' int __ret_warn_on = !!(condition); \ ^ mm/mmap.c:2858:46: note: each undeclared identifier is reported only once for each function it appears in round_up(FIRST_USER_ADDRESS, PUD_SIZE) >> PUD_SHIFT); ^ include/asm-generic/bug.h:86:25: note: in definition of macro 'WARN_ON' int __ret_warn_on = !!(condition); \ ^ As with <asm-generic/pgtable-nopud.h>, let's define PUD_SHIFT to PGDIR_SHIFT. Signed-off-by:Wu Fengguang <fengguang.wu@intel.com> Signed-off-by:
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Kirill A. Shutemov authored
LKP has triggered a compiler warning after my recent patch "mm: account pmd page tables to the process": mm/mmap.c: In function 'exit_mmap': >> mm/mmap.c:2857:2: warning: right shift count >= width of type [enabled by default] The code: > 2857 WARN_ON(mm_nr_pmds(mm) > 2858 round_up(FIRST_USER_ADDRESS, PUD_SIZE) >> PUD_SHIFT); In this, on tile, we have FIRST_USER_ADDRESS defined as 0. round_up() has the same type -- int. PUD_SHIFT. I think the best way to fix it is to define FIRST_USER_ADDRESS as unsigned long. On every arch for consistency. Signed-off-by: -
Kirill A. Shutemov authored
Microblaze uses custom implementation of PMD folding, but doesn't define __PAGETABLE_PMD_FOLDED, which generic code expects to see. Let's fix it. Defining __PAGETABLE_PMD_FOLDED will drop out unused __pmd_alloc(). It also fixes problems with recently-introduced pmd accounting. Signed-off-by:
Guenter Roeck <linux@roeck-us.net> Tested-by:
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Johannes Weiner authored
The swap controller code is scattered all over the file. Gather all the code that isn't directly needed by the memory controller at the end of the file in its own CONFIG_MEMCG_SWAP section. Signed-off-by:
Vladimir Davydov <vdavydov@parallels.com> Signed-off-by:
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Johannes Weiner authored
The initialization code for the per-cpu charge stock and the soft limit tree is compact enough to inline it into mem_cgroup_init(). Signed-off-by:
Michal Hocko <mhocko@suse.cz> Reviewed-by:
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Johannes Weiner authored
- No need to test the node for N_MEMORY. node_online() is enough for node fallback to work in slab, use NUMA_NO_NODE for everything else. - Remove the BUG_ON() for allocation failure. A NULL pointer crash is just as descriptive, and the absent return value check is obvious. - Move local variables to the inner-most blocks. - Point to the tree structure after its initialized, not before, it's just more logical that way. Signed-off-by:
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George G. Davis authored
The totalcma_pages variable is not updated to account for CMA regions defined via device tree reserved-memory sub-nodes. Fix this omission by moving the calculation of totalcma_pages into cma_init_reserved_mem() instead of cma_declare_contiguous() such that it will include reserved memory used by all CMA regions. Signed-off-by:
George G. Davis <george_davis@mentor.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Acked-by:
Michal Nazarewicz <mina86@mina86.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> Signed-off-by:
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Michal Hocko authored
Commit 5695be14 ("OOM, PM: OOM killed task shouldn't escape PM suspend") has left a race window when OOM killer manages to note_oom_kill after freeze_processes checks the counter. The race window is quite small and really unlikely and partial solution deemed sufficient at the time of submission. Tejun wasn't happy about this partial solution though and insisted on a full solution. That requires the full OOM and freezer's task freezing exclusion, though. This is done by this patch which introduces oom_sem RW lock and turns oom_killer_disable() into a full OOM barrier. oom_killer_disabled check is moved from the allocation path to the OOM level and we take oom_sem for reading for both the check and the whole OOM invocation. oom_killer_disable() takes oom_sem for writing so it waits for all currently running OOM killer invocations. Then it disable all the further OOMs by setting oom_killer_disabled and checks for any oom victims. Victims are counted via mark_tsk_oom_victim resp. unmark_oom_victim. The last victim wakes up all waiters enqueued by oom_killer_disable(). Therefore this function acts as the full OOM barrier. The page fault path is covered now as well although it was assumed to be safe before. As per Tejun, "We used to have freezing points deep in file system code which may be reacheable from page fault." so it would be better and more robust to not rely on freezing points here. Same applies to the memcg OOM killer. out_of_memory tells the caller whether the OOM was allowed to trigger and the callers are supposed to handle the situation. The page allocation path simply fails the allocation same as before. The page fault path will retry the fault (more on that later) and Sysrq OOM trigger will simply complain to the log. Normally there wouldn't be any unfrozen user tasks after try_to_freeze_tasks so the function will not block. But if there was an OOM killer racing with try_to_freeze_tasks and the OOM victim didn't finish yet then we have to wait for it. This should complete in a finite time, though, because - the victim cannot loop in the page fault handler (it would die on the way out from the exception) - it cannot loop in the page allocator because all the further allocation would fail and __GFP_NOFAIL allocations are not acceptable at this stage - it shouldn't be blocked on any locks held by frozen tasks (try_to_freeze expects lockless context) and kernel threads and work queues are not frozen yet Signed-off-by:
Tejun Heo <tj@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Signed-off-by:
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Michal Hocko authored
While touching this area let's convert printk to pr_*. This also makes the printing of continuation lines done properly. Signed-off-by:
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Michal Hocko authored
While touching this area let's convert printk to pr_*. This also makes the printing of continuation lines done properly. Signed-off-by:
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