linux/mm/page_alloc.c, branch v4.8

mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator

2016-09-02T00:52:01Z

Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts of memory when booting a secondary kernel. Srikar Dronamraju reported that multiple nodes may have no memory managed by the buddy allocator but still return true for populated_zone(). Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of nodes") was reported to cause kswapd to spin at 100% CPU usage when fadump was enabled. The old code happened to deal with the situation of a populated node with zero free pages by co-incidence but the current code tries to reclaim populated zones without realising that is impossible. We cannot just convert populated_zone() as many existing users really need to check for present_pages. This patch introduces a managed_zone() helper and uses it in the few cases where it is critical that the check is made for managed pages -- zonelist construction and page reclaim. Link: http://lkml.kernel.org/r/20160831195104.GB8119@techsingularity.net Signed-off-by: Mel Gorman Reported-by: Srikar Dronamraju Tested-by: Srikar Dronamraju Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, oom: prevent premature OOM killer invocation for high order request

2016-09-02T00:52:01Z

There have been several reports about pre-mature OOM killer invocation in 4.7 kernel when order-2 allocation request (for the kernel stack) invoked OOM killer even during basic workloads (light IO or even kernel compile on some filesystems). In all reported cases the memory is fragmented and there are no order-2+ pages available. There is usually a large amount of slab memory (usually dentries/inodes) and further debugging has shown that there are way too many unmovable blocks which are skipped during the compaction. Multiple reporters have confirmed that the current linux-next which includes [1] and [2] helped and OOMs are not reproducible anymore. A simpler fix for the late rc and stable is to simply ignore the compaction feedback and retry as long as there is a reclaim progress and we are not getting OOM for order-0 pages. We already do that for CONFING_COMPACTION=n so let's reuse the same code when compaction is enabled as well. [1] http://lkml.kernel.org/r/20160810091226.6709-1-vbabka@suse.cz [2] http://lkml.kernel.org/r/f7a9ea9d-bb88-bfd6-e340-3a933559305a@suse.cz Fixes: 0a0337e0d1d1 ("mm, oom: rework oom detection") Link: http://lkml.kernel.org/r/20160823074339.GB23577@dhcp22.suse.cz Signed-off-by: Michal Hocko Tested-by: Olaf Hering Tested-by: Ralf-Peter Rohbeck Cc: Markus Trippelsdorf Cc: Arkadiusz Miskiewicz Cc: Ralf-Peter Rohbeck Cc: Jiri Slaby Cc: Vlastimil Babka Cc: Joonsoo Kim Cc: Tetsuo Handa Cc: David Rientjes Cc: [4.7.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc, meminfo: use correct helpers for calculating LRU sizes in meminfo

2016-08-11T23:58:13Z

meminfo_proc_show() and si_mem_available() are using the wrong helpers for calculating the size of the LRUs. The user-visible impact is that there appears to be an abnormally high number of unevictable pages. Link: http://lkml.kernel.org/r/20160805105805.GR2799@techsingularity.net Signed-off-by: Mel Gorman Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_alloc.c: recalculate some of node threshold when on/offline memory

2016-08-10T23:40:56Z

Some of node threshold depends on number of managed pages in the node. When memory is going on/offline, it can be changed and we need to adjust them. Add recalculation to appropriate places and clean-up related functions for better maintenance. Link: http://lkml.kernel.org/r/1470724248-26780-2-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Acked-by: Mel Gorman Cc: Vlastimil Babka Cc: Johannes Weiner Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_alloc.c: fix wrong initialization when sysctl_min_unmapped_ratio changes

2016-08-10T23:40:56Z

Before resetting min_unmapped_pages, we need to initialize min_unmapped_pages rather than min_slab_pages. Fixes: a5f5f91da6 (mm: convert zone_reclaim to node_reclaim) Link: http://lkml.kernel.org/r/1470724248-26780-1-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim Acked-by: Mel Gorman Cc: Vlastimil Babka Cc: Johannes Weiner Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: memcontrol: only mark charged pages with PageKmemcg

2016-08-09T17:14:10Z

To distinguish non-slab pages charged to kmemcg we mark them PageKmemcg, which sets page->_mapcount to -512. Currently, we set/clear PageKmemcg in __alloc_pages_nodemask()/free_pages_prepare() for any page allocated with __GFP_ACCOUNT, including those that aren't actually charged to any cgroup, i.e. allocated from the root cgroup context. To avoid overhead in case cgroups are not used, we only do that if memcg_kmem_enabled() is true. The latter is set iff there are kmem-enabled memory cgroups (online or offline). The root cgroup is not considered kmem-enabled. As a result, if a page is allocated with __GFP_ACCOUNT for the root cgroup when there are kmem-enabled memory cgroups and is freed after all kmem-enabled memory cgroups were removed, e.g. # no memory cgroups has been created yet, create one mkdir /sys/fs/cgroup/memory/test # run something allocating pages with __GFP_ACCOUNT, e.g. # a program using pipe dmesg | tail # remove the memory cgroup rmdir /sys/fs/cgroup/memory/test we'll get bad page state bug complaining about page->_mapcount != -1: BUG: Bad page state in process swapper/0 pfn:1fd945c page:ffffea007f651700 count:0 mapcount:-511 mapping: (null) index:0x0 flags: 0x1000000000000000() To avoid that, let's mark with PageKmemcg only those pages that are actually charged to and hence pin a non-root memory cgroup. Fixes: 4949148ad433 ("mm: charge/uncharge kmemcg from generic page allocator paths") Reported-and-tested-by: Eric Dumazet Signed-off-by: Vladimir Davydov Signed-off-by: Linus Torvalds

mm: initialise per_cpu_nodestats for all online pgdats at boot

2016-08-05T00:02:09Z

Paul Mackerras and Reza Arbab reported that machines with memoryless nodes fail when vmstats are refreshed. Paul reported an oops as follows Unable to handle kernel paging request for data at address 0xff7a10000 Faulting instruction address: 0xc000000000270cd0 Oops: Kernel access of bad area, sig: 11 [#1] SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.7.0-kvm+ #118 task: c000000ff0680010 task.stack: c000000ff0704000 NIP: c000000000270cd0 LR: c000000000270ce8 CTR: 0000000000000000 REGS: c000000ff0707900 TRAP: 0300 Not tainted (4.7.0-kvm+) MSR: 9000000102009033 CR: 846b6824 XER: 20000000 CFAR: c000000000008768 DAR: 0000000ff7a10000 DSISR: 42000000 SOFTE: 1 NIP refresh_zone_stat_thresholds+0x80/0x240 LR refresh_zone_stat_thresholds+0x98/0x240 Call Trace: refresh_zone_stat_thresholds+0xb8/0x240 (unreliable) Both supplied potential fixes but one potentially misses checks and another had redundant initialisations. This version initialises per_cpu_nodestats on a per-pgdat basis instead of on a per-zone basis. Link: http://lkml.kernel.org/r/20160804092404.GI2799@techsingularity.net Signed-off-by: Mel Gorman Reported-by: Paul Mackerras Reported-by: Reza Arbab Tested-by: Reza Arbab Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

treewide: replace obsolete _refok by __ref

2016-08-02T21:31:41Z

There was only one use of __initdata_refok and __exit_refok __init_refok was used 46 times against 82 for __ref. Those definitions are obsolete since commit 312b1485fb50 ("Introduce new section reference annotations tags: __ref, __refdata, __refconst") This patch removes the following compatibility definitions and replaces them treewide. /* compatibility defines */ #define __init_refok __ref #define __initdata_refok __refdata #define __exit_refok __ref I can also provide separate patches if necessary. (One patch per tree and check in 1 month or 2 to remove old definitions) [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1466796271-3043-1-git-send-email-fabf@skynet.be Signed-off-by: Fabian Frederick Cc: Ingo Molnar Cc: Sam Ravnborg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: simplify contended compaction handling

2016-07-28T23:07:41Z

Async compaction detects contention either due to failing trylock on zone->lock or lru_lock, or by need_resched(). Since 1f9efdef4f3f ("mm, compaction: khugepaged should not give up due to need_resched()") the code got quite complicated to distinguish these two up to the __alloc_pages_slowpath() level, so different decisions could be taken for khugepaged allocations. After the recent changes, khugepaged allocations don't check for contended compaction anymore, so we again don't need to distinguish lock and sched contention, and simplify the current convoluted code a lot. However, I believe it's also possible to simplify even more and completely remove the check for contended compaction after the initial async compaction for costly orders, which was originally aimed at THP page fault allocations. There are several reasons why this can be done now: - with the new defaults, THP page faults no longer do reclaim/compaction at all, unless the system admin has overridden the default, or application has indicated via madvise that it can benefit from THP's. In both cases, it means that the potential extra latency is expected and worth the benefits. - even if reclaim/compaction proceeds after this patch where it previously wouldn't, the second compaction attempt is still async and will detect the contention and back off, if the contention persists - there are still heuristics like deferred compaction and pageblock skip bits in place that prevent excessive THP page fault latencies Link: http://lkml.kernel.org/r/20160721073614.24395-9-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, compaction: introduce direct compaction priority

2016-07-28T23:07:41Z

In the context of direct compaction, for some types of allocations we would like the compaction to either succeed or definitely fail while trying as hard as possible. Current async/sync_light migration mode is insufficient, as there are heuristics such as caching scanner positions, marking pageblocks as unsuitable or deferring compaction for a zone. At least the final compaction attempt should be able to override these heuristics. To communicate how hard compaction should try, we replace migration mode with a new enum compact_priority and change the relevant function signatures. In compact_zone_order() where struct compact_control is constructed, the priority is mapped to suitable control flags. This patch itself has no functional change, as the current priority levels are mapped back to the same migration modes as before. Expanding them will be done next. Note that !CONFIG_COMPACTION variant of try_to_compact_pages() is removed, as the only caller exists under CONFIG_COMPACTION. Link: http://lkml.kernel.org/r/20160721073614.24395-8-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds