kernel/linux.git/include/linux/slab.h, branch linux-4.20.y

mm, slab/slub: introduce kmalloc-reclaimable caches

2018-10-26T23:26:31+00:00

Kmem caches can be created with a SLAB_RECLAIM_ACCOUNT flag, which indicates they contain objects which can be reclaimed under memory pressure (typically through a shrinker). This makes the slab pages accounted as NR_SLAB_RECLAIMABLE in vmstat, which is reflected also the MemAvailable meminfo counter and in overcommit decisions. The slab pages are also allocated with __GFP_RECLAIMABLE, which is good for anti-fragmentation through grouping pages by mobility. The generic kmalloc-X caches are created without this flag, but sometimes are used also for objects that can be reclaimed, which due to varying size cannot have a dedicated kmem cache with SLAB_RECLAIM_ACCOUNT flag. A prominent example are dcache external names, which prompted the creation of a new, manually managed vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES in commit f1782c9bc547 ("dcache: account external names as indirectly reclaimable memory"). To better handle this and any other similar cases, this patch introduces SLAB_RECLAIM_ACCOUNT variants of kmalloc caches, named kmalloc-rcl-X. They are used whenever the kmalloc() call passes __GFP_RECLAIMABLE among gfp flags. They are added to the kmalloc_caches array as a new type. Allocations with both __GFP_DMA and __GFP_RECLAIMABLE will use a dma type cache. This change only applies to SLAB and SLUB, not SLOB. This is fine, since SLOB's target are tiny system and this patch does add some overhead of kmem management objects. Link: http://lkml.kernel.org/r/20180731090649.16028-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman Acked-by: Christoph Lameter Acked-by: Roman Gushchin Cc: David Rientjes Cc: Johannes Weiner Cc: Joonsoo Kim Cc: Laura Abbott Cc: Matthew Wilcox Cc: Michal Hocko Cc: Sumit Semwal Cc: Vijayanand Jitta Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, slab: combine kmalloc_caches and kmalloc_dma_caches

2018-10-26T23:26:31+00:00

Patch series "kmalloc-reclaimable caches", v4. As discussed at LSF/MM [1] here's a patchset that introduces kmalloc-reclaimable caches (more details in the second patch) and uses them for dcache external names. That allows us to repurpose the NR_INDIRECTLY_RECLAIMABLE_BYTES counter later in the series. With patch 3/6, dcache external names are allocated from kmalloc-rcl-* caches, eliminating the need for manual accounting. More importantly, it also ensures the reclaimable kmalloc allocations are grouped in pages separate from the regular kmalloc allocations. The need for proper accounting of dcache external names has shown it's easy for misbehaving process to allocate lots of them, causing premature OOMs. Without the added grouping, it's likely that a similar workload can interleave the dcache external names allocations with regular kmalloc allocations (note: I haven't searched myself for an example of such regular kmalloc allocation, but I would be very surprised if there wasn't some). A pathological case would be e.g. one 64byte regular allocations with 63 external dcache names in a page (64x64=4096), which means the page is not freed even after reclaiming after all dcache names, and the process can thus "steal" the whole page with single 64byte allocation. If other kmalloc users similar to dcache external names become identified, they can also benefit from the new functionality simply by adding __GFP_RECLAIMABLE to the kmalloc calls. Side benefits of the patchset (that could be also merged separately) include removed branch for detecting __GFP_DMA kmalloc(), and shortening kmalloc cache names in /proc/slabinfo output. The latter is potentially an ABI break in case there are tools parsing the names and expecting the values to be in bytes. This is how /proc/slabinfo looks like after booting in virtme: ... kmalloc-rcl-4M 0 0 4194304 1 1024 : tunables 1 1 0 : slabdata 0 0 0 ... kmalloc-rcl-96 7 32 128 32 1 : tunables 120 60 8 : slabdata 1 1 0 kmalloc-rcl-64 25 128 64 64 1 : tunables 120 60 8 : slabdata 2 2 0 kmalloc-rcl-32 0 0 32 124 1 : tunables 120 60 8 : slabdata 0 0 0 kmalloc-4M 0 0 4194304 1 1024 : tunables 1 1 0 : slabdata 0 0 0 kmalloc-2M 0 0 2097152 1 512 : tunables 1 1 0 : slabdata 0 0 0 kmalloc-1M 0 0 1048576 1 256 : tunables 1 1 0 : slabdata 0 0 0 ... /proc/vmstat with renamed nr_indirectly_reclaimable_bytes counter: ... nr_slab_reclaimable 2817 nr_slab_unreclaimable 1781 ... nr_kernel_misc_reclaimable 0 ... /proc/meminfo with new KReclaimable counter: ... Shmem: 564 kB KReclaimable: 11260 kB Slab: 18368 kB SReclaimable: 11260 kB SUnreclaim: 7108 kB KernelStack: 1248 kB ... This patch (of 6): The kmalloc caches currently mainain separate (optional) array kmalloc_dma_caches for __GFP_DMA allocations. There are tests for __GFP_DMA in the allocation hotpaths. We can avoid the branches by combining kmalloc_caches and kmalloc_dma_caches into a single two-dimensional array where the outer dimension is cache "type". This will also allow to add kmalloc-reclaimable caches as a third type. Link: http://lkml.kernel.org/r/20180731090649.16028-2-vbabka@suse.cz Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman Acked-by: Christoph Lameter Acked-by: Roman Gushchin Cc: Michal Hocko Cc: Johannes Weiner Cc: David Rientjes Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Laura Abbott Cc: Sumit Semwal Cc: Vijayanand Jitta Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB

2018-08-17T23:20:30+00:00

Introduce new config option, which is used to replace repeating CONFIG_MEMCG && !CONFIG_SLOB pattern. Next patches add a little more memcg+kmem related code, so let's keep the defines more clearly. Link: http://lkml.kernel.org/r/153063053670.1818.15013136946600481138.stgit@localhost.localdomain Signed-off-by: Kirill Tkhai Acked-by: Vladimir Davydov Tested-by: Shakeel Butt Cc: Al Viro Cc: Andrey Ryabinin Cc: Chris Wilson Cc: Greg Kroah-Hartman Cc: Guenter Roeck Cc: "Huang, Ying" Cc: Johannes Weiner Cc: Josef Bacik Cc: Li RongQing Cc: Matthew Wilcox Cc: Matthias Kaehlcke Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Philippe Ombredanne Cc: Roman Gushchin Cc: Sahitya Tummala Cc: Stephen Rothwell Cc: Tetsuo Handa Cc: Thomas Gleixner Cc: Waiman Long Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: fix race between kmem_cache destroy, create and deactivate

2018-06-14T22:55:23+00:00

The memcg kmem cache creation and deactivation (SLUB only) is asynchronous. If a root kmem cache is destroyed whose memcg cache is in the process of creation or deactivation, the kernel may crash. Example of one such crash: general protection fault: 0000 [#1] SMP PTI CPU: 1 PID: 1721 Comm: kworker/14:1 Not tainted 4.17.0-smp ... Workqueue: memcg_kmem_cache kmemcg_deactivate_workfn RIP: 0010:has_cpu_slab ... Call Trace: ? on_each_cpu_cond __kmem_cache_shrink kmemcg_cache_deact_after_rcu kmemcg_deactivate_workfn process_one_work worker_thread kthread ret_from_fork+0x35/0x40 To fix this race, on root kmem cache destruction, mark the cache as dying and flush the workqueue used for memcg kmem cache creation and deactivation. SLUB's memcg kmem cache deactivation also includes RCU callback and thus make sure all previous registered RCU callbacks have completed as well. [shakeelb@google.com: handle the RCU callbacks for SLUB deactivation] Link: http://lkml.kernel.org/r/20180611192951.195727-1-shakeelb@google.com [shakeelb@google.com: add more documentation, rename fields for readability] Link: http://lkml.kernel.org/r/20180522201336.196994-1-shakeelb@google.com [akpm@linux-foundation.org: fix build, per Shakeel] [shakeelb@google.com: v3. Instead of refcount, flush the workqueue] Link: http://lkml.kernel.org/r/20180530001204.183758-1-shakeelb@google.com Link: http://lkml.kernel.org/r/20180521174116.171846-1-shakeelb@google.com Signed-off-by: Shakeel Butt Acked-by: Vladimir Davydov Cc: Michal Hocko Cc: Greg Thelen Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Johannes Weiner Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: Use overflow helpers in kmalloc_array*()

2018-06-05T19:16:51+00:00

Instead of open-coded multiplication and bounds checking, use the new overflow helper. Suggested-by: Rasmus Villemoes Signed-off-by: Kees Cook

headers: untangle kmemleak.h from mm.h

2018-04-06T04:36:27+00:00

Currently #includes for no obvious reason. It looks like it's only a convenience, so remove kmemleak.h from slab.h and add to any users of kmemleak_* that don't already #include it. Also remove from source files that do not use it. This is tested on i386 allmodconfig and x86_64 allmodconfig. It would be good to run it through the 0day bot for other $ARCHes. I have neither the horsepower nor the storage space for the other $ARCHes. Update: This patch has been extensively build-tested by both the 0day bot & kisskb/ozlabs build farms. Both of them reported 2 build failures for which patches are included here (in v2). [ slab.h is the second most used header file after module.h; kernel.h is right there with slab.h. There could be some minor error in the counting due to some #includes having comments after them and I didn't combine all of those. ] [akpm@linux-foundation.org: security/keys/big_key.c needs vmalloc.h, per sfr] Link: http://lkml.kernel.org/r/e4309f98-3749-93e1-4bb7-d9501a39d015@infradead.org Link: http://kisskb.ellerman.id.au/kisskb/head/13396/ Signed-off-by: Randy Dunlap Reviewed-by: Ingo Molnar Reported-by: Michael Ellerman [2 build failures] Reported-by: Fengguang Wu [2 build failures] Reviewed-by: Andrew Morton Cc: Wei Yongjun Cc: Luis R. Rodriguez Cc: Greg Kroah-Hartman Cc: Mimi Zohar Cc: John Johansen Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab: make usercopy region 32-bit

2018-04-06T04:36:24+00:00

If kmem case sizes are 32-bit, then usecopy region should be too. Link: http://lkml.kernel.org/r/20180305200730.15812-21-adobriyan@gmail.com Signed-off-by: Alexey Dobriyan Cc: David Miller Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab: make kmem_cache_create() work with 32-bit sizes

2018-04-06T04:36:23+00:00

struct kmem_cache::size and ::align were always 32-bit. Out of curiosity I created 4GB kmem_cache, it oopsed with division by 0. kmem_cache_create(1UL<<32+1) created 1-byte cache as expected. size_t doesn't work and never did. Link: http://lkml.kernel.org/r/20180305200730.15812-6-adobriyan@gmail.com Signed-off-by: Alexey Dobriyan Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab: make kmalloc_size() return "unsigned int"

2018-04-06T04:36:23+00:00

kmalloc_size() derives size of kmalloc cache from internal index, which can't be negative. Propagate unsignedness a bit. Link: http://lkml.kernel.org/r/20180305200730.15812-3-adobriyan@gmail.com Signed-off-by: Alexey Dobriyan Acked-by: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab: make kmalloc_index() return "unsigned int"

2018-04-06T04:36:23+00:00

kmalloc_index() return index into an array of kmalloc kmem caches, therefore should be unsigned. Space savings with SLUB on trimmed down .config: add/remove: 0/1 grow/shrink: 6/56 up/down: 85/-557 (-472) Function old new delta calculate_sizes 924 983 +59 on_freelist 589 604 +15 init_cache_random_seq 122 127 +5 ext4_mb_init 1206 1210 +4 slab_pad_check.part 270 271 +1 cpu_partial_store 112 113 +1 usersize_show 28 27 -1 ... new_slab 1871 1837 -34 slab_order 204 - -204 This patch start a series of converting SLUB (mostly) to "unsigned int". 1) Most integers in the code are in fact unsigned entities: array indexes, lengths, buffer sizes, allocation orders. It is therefore better to use unsigned variables 2) Some integers in the code are either "size_t" or "unsigned long" for no reason. size_t usually comes from people trying to maintain type correctness and figuring out that "sizeof" operator returns size_t or memset/memcpy takes size_t so should everything passed to it. However the number of 4GB+ objects in the kernel is very small. Most, if not all, dynamically allocated objects with kmalloc() or kmem_cache_create() aren't actually big. Maintaining wide types doesn't do anything. 64-bit ops are bigger than 32-bit on our beloved x86_64, so try to not use 64-bit where it isn't necessary (read: everywhere where integers are integers not pointers) 3) in case of SLAB allocators, there are additional limitations *) page->inuse, page->objects are only 16-/15-bit, *) cache size was always 32-bit *) slab orders are small, order 20 is needed to go 64-bit on x86_64 (PAGE_SIZE << order) Basically everything is 32-bit except kmalloc(1ULL<<32) which gets shortcut through page allocator. Christoph said: : : That changes with large base page size on power and ARM64 f.e. but then : we do not want to encourage larger allocations through slab anyways. Link: http://lkml.kernel.org/r/20180305200730.15812-2-adobriyan@gmail.com Signed-off-by: Alexey Dobriyan Acked-by: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds