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authorMinchan Kim <minchan@kernel.org>2014-05-28 15:53:59 +0900
committerLinus Torvalds <torvalds@linux-foundation.org>2014-05-30 11:52:51 -0700
commit6538b8ea886e472f4431db8ca1d60478f838d14b (patch)
tree041d59e78d5eb9385d8f4eba8eb368113c305be2
parent6f6111e4a73d0f6370eb8be4f8e4523210b6a67d (diff)
downloadlinux-6538b8ea886e472f4431db8ca1d60478f838d14b.tar.gz
x86_64: expand kernel stack to 16K
While I play inhouse patches with much memory pressure on qemu-kvm, 3.14 kernel was randomly crashed. The reason was kernel stack overflow. When I investigated the problem, the callstack was a little bit deeper by involve with reclaim functions but not direct reclaim path. I tried to diet stack size of some functions related with alloc/reclaim so did a hundred of byte but overflow was't disappeard so that I encounter overflow by another deeper callstack on reclaim/allocator path. Of course, we might sweep every sites we have found for reducing stack usage but I'm not sure how long it saves the world(surely, lots of developer start to add nice features which will use stack agains) and if we consider another more complex feature in I/O layer and/or reclaim path, it might be better to increase stack size( meanwhile, stack usage on 64bit machine was doubled compared to 32bit while it have sticked to 8K. Hmm, it's not a fair to me and arm64 already expaned to 16K. ) So, my stupid idea is just let's expand stack size and keep an eye toward stack consumption on each kernel functions via stacktrace of ftrace. For example, we can have a bar like that each funcion shouldn't exceed 200K and emit the warning when some function consumes more in runtime. Of course, it could make false positive but at least, it could make a chance to think over it. I guess this topic was discussed several time so there might be strong reason not to increase kernel stack size on x86_64, for me not knowing so Ccing x86_64 maintainers, other MM guys and virtio maintainers. Here's an example call trace using up the kernel stack: Depth Size Location (51 entries) ----- ---- -------- 0) 7696 16 lookup_address 1) 7680 16 _lookup_address_cpa.isra.3 2) 7664 24 __change_page_attr_set_clr 3) 7640 392 kernel_map_pages 4) 7248 256 get_page_from_freelist 5) 6992 352 __alloc_pages_nodemask 6) 6640 8 alloc_pages_current 7) 6632 168 new_slab 8) 6464 8 __slab_alloc 9) 6456 80 __kmalloc 10) 6376 376 vring_add_indirect 11) 6000 144 virtqueue_add_sgs 12) 5856 288 __virtblk_add_req 13) 5568 96 virtio_queue_rq 14) 5472 128 __blk_mq_run_hw_queue 15) 5344 16 blk_mq_run_hw_queue 16) 5328 96 blk_mq_insert_requests 17) 5232 112 blk_mq_flush_plug_list 18) 5120 112 blk_flush_plug_list 19) 5008 64 io_schedule_timeout 20) 4944 128 mempool_alloc 21) 4816 96 bio_alloc_bioset 22) 4720 48 get_swap_bio 23) 4672 160 __swap_writepage 24) 4512 32 swap_writepage 25) 4480 320 shrink_page_list 26) 4160 208 shrink_inactive_list 27) 3952 304 shrink_lruvec 28) 3648 80 shrink_zone 29) 3568 128 do_try_to_free_pages 30) 3440 208 try_to_free_pages 31) 3232 352 __alloc_pages_nodemask 32) 2880 8 alloc_pages_current 33) 2872 200 __page_cache_alloc 34) 2672 80 find_or_create_page 35) 2592 80 ext4_mb_load_buddy 36) 2512 176 ext4_mb_regular_allocator 37) 2336 128 ext4_mb_new_blocks 38) 2208 256 ext4_ext_map_blocks 39) 1952 160 ext4_map_blocks 40) 1792 384 ext4_writepages 41) 1408 16 do_writepages 42) 1392 96 __writeback_single_inode 43) 1296 176 writeback_sb_inodes 44) 1120 80 __writeback_inodes_wb 45) 1040 160 wb_writeback 46) 880 208 bdi_writeback_workfn 47) 672 144 process_one_work 48) 528 112 worker_thread 49) 416 240 kthread 50) 176 176 ret_from_fork [ Note: the problem is exacerbated by certain gcc versions that seem to generate much bigger stack frames due to apparently bad coalescing of temporaries and generating too many spills. Rusty saw gcc-4.6.4 using 35% more stack on the virtio path than 4.8.2 does, for example. Minchan not only uses such a bad gcc version (4.6.3 in his case), but some of the stack use is due to debugging (CONFIG_DEBUG_PAGEALLOC is what causes that kernel_map_pages() frame, for example). But we're clearly getting too close. The VM code also seems to have excessive stack frames partly for the same compiler reason, triggered by excessive inlining and lots of function arguments. We need to improve on our stack use, but in the meantime let's do this simple stack increase too. Unlike most earlier reports, there is nothing simple that stands out as being really horribly wrong here, apart from the fact that the stack frames are just bigger than they should need to be. - Linus ] Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Peter Anvin <hpa@zytor.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Jones <davej@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michael S Tsirkin <mst@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: PJ Waskiewicz <pjwaskiewicz@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/include/asm/page_64_types.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 8de6d9cf3b9..678205195ae 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -1,7 +1,7 @@
#ifndef _ASM_X86_PAGE_64_DEFS_H
#define _ASM_X86_PAGE_64_DEFS_H
-#define THREAD_SIZE_ORDER 1
+#define THREAD_SIZE_ORDER 2
#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
#define CURRENT_MASK (~(THREAD_SIZE - 1))