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. [ 1065.604404] kworker/-5766 0d..2 1071625990us : stack_trace_call: Depth Size Location (51 entries) [ 1065.604404] ----- ---- -------- [ 1065.604404] kworker/-5766 0d..2 1071625991us : stack_trace_call: 0) 7696 16 lookup_address+0x28/0x30 [ 1065.604404] kworker/-5766 0d..2 1071625991us : stack_trace_call: 1) 7680 16 _lookup_address_cpa.isra.3+0x3b/0x40 [ 1065.604404] kworker/-5766 0d..2 1071625991us : stack_trace_call: 2) 7664 24 __change_page_attr_set_clr+0xe0/0xb50 [ 1065.604404] kworker/-5766 0d..2 1071625991us : stack_trace_call: 3) 7640 392 kernel_map_pages+0x6c/0x120 [ 1065.604404] kworker/-5766 0d..2 1071625992us : stack_trace_call: 4) 7248 256 get_page_from_freelist+0x489/0x920 [ 1065.604404] kworker/-5766 0d..2 1071625992us : stack_trace_call: 5) 6992 352 __alloc_pages_nodemask+0x5e1/0xb20 [ 1065.604404] kworker/-5766 0d..2 1071625992us : stack_trace_call: 6) 6640 8 alloc_pages_current+0x10f/0x1f0 [ 1065.604404] kworker/-5766 0d..2 1071625992us : stack_trace_call: 7) 6632 168 new_slab+0x2c5/0x370 [ 1065.604404] kworker/-5766 0d..2 1071625992us : stack_trace_call: 8) 6464 8 __slab_alloc+0x3a9/0x501 [ 1065.604404] kworker/-5766 0d..2 1071625993us : stack_trace_call: 9) 6456 80 __kmalloc+0x1cb/0x200 [ 1065.604404] kworker/-5766 0d..2 1071625993us : stack_trace_call: 10) 6376 376 vring_add_indirect+0x36/0x200 [ 1065.604404] kworker/-5766 0d..2 1071625993us : stack_trace_call: 11) 6000 144 virtqueue_add_sgs+0x2e2/0x320 [ 1065.604404] kworker/-5766 0d..2 1071625993us : stack_trace_call: 12) 5856 288 __virtblk_add_req+0xda/0x1b0 [ 1065.604404] kworker/-5766 0d..2 1071625993us : stack_trace_call: 13) 5568 96 virtio_queue_rq+0xd3/0x1d0 [ 1065.604404] kworker/-5766 0d..2 1071625994us : stack_trace_call: 14) 5472 128 __blk_mq_run_hw_queue+0x1ef/0x440 [ 1065.604404] kworker/-5766 0d..2 1071625994us : stack_trace_call: 15) 5344 16 blk_mq_run_hw_queue+0x35/0x40 [ 1065.604404] kworker/-5766 0d..2 1071625994us : stack_trace_call: 16) 5328 96 blk_mq_insert_requests+0xdb/0x160 [ 1065.604404] kworker/-5766 0d..2 1071625994us : stack_trace_call: 17) 5232 112 blk_mq_flush_plug_list+0x12b/0x140 [ 1065.604404] kworker/-5766 0d..2 1071625994us : stack_trace_call: 18) 5120 112 blk_flush_plug_list+0xc7/0x220 [ 1065.604404] kworker/-5766 0d..2 1071625995us : stack_trace_call: 19) 5008 64 io_schedule_timeout+0x88/0x100 [ 1065.604404] kworker/-5766 0d..2 1071625995us : stack_trace_call: 20) 4944 128 mempool_alloc+0x145/0x170 [ 1065.604404] kworker/-5766 0d..2 1071625995us : stack_trace_call: 21) 4816 96 bio_alloc_bioset+0x10b/0x1d0 [ 1065.604404] kworker/-5766 0d..2 1071625995us : stack_trace_call: 22) 4720 48 get_swap_bio+0x30/0x90 [ 1065.604404] kworker/-5766 0d..2 1071625995us : stack_trace_call: 23) 4672 160 __swap_writepage+0x150/0x230 [ 1065.604404] kworker/-5766 0d..2 1071625996us : stack_trace_call: 24) 4512 32 swap_writepage+0x42/0x90 [ 1065.604404] kworker/-5766 0d..2 1071625996us : stack_trace_call: 25) 4480 320 shrink_page_list+0x676/0xa80 [ 1065.604404] kworker/-5766 0d..2 1071625996us : stack_trace_call: 26) 4160 208 shrink_inactive_list+0x262/0x4e0 [ 1065.604404] kworker/-5766 0d..2 1071625996us : stack_trace_call: 27) 3952 304 shrink_lruvec+0x3e1/0x6a0 [ 1065.604404] kworker/-5766 0d..2 1071625996us : stack_trace_call: 28) 3648 80 shrink_zone+0x3f/0x110 [ 1065.604404] kworker/-5766 0d..2 1071625997us : stack_trace_call: 29) 3568 128 do_try_to_free_pages+0x156/0x4c0 [ 1065.604404] kworker/-5766 0d..2 1071625997us : stack_trace_call: 30) 3440 208 try_to_free_pages+0xf7/0x1e0 [ 1065.604404] kworker/-5766 0d..2 1071625997us : stack_trace_call: 31) 3232 352 __alloc_pages_nodemask+0x783/0xb20 [ 1065.604404] kworker/-5766 0d..2 1071625997us : stack_trace_call: 32) 2880 8 alloc_pages_current+0x10f/0x1f0 [ 1065.604404] kworker/-5766 0d..2 1071625997us : stack_trace_call: 33) 2872 200 __page_cache_alloc+0x13f/0x160 [ 1065.604404] kworker/-5766 0d..2 1071625998us : stack_trace_call: 34) 2672 80 find_or_create_page+0x4c/0xb0 [ 1065.604404] kworker/-5766 0d..2 1071625998us : stack_trace_call: 35) 2592 80 ext4_mb_load_buddy+0x1e9/0x370 [ 1065.604404] kworker/-5766 0d..2 1071625998us : stack_trace_call: 36) 2512 176 ext4_mb_regular_allocator+0x1b7/0x460 [ 1065.604404] kworker/-5766 0d..2 1071625998us : stack_trace_call: 37) 2336 128 ext4_mb_new_blocks+0x458/0x5f0 [ 1065.604404] kworker/-5766 0d..2 1071625998us : stack_trace_call: 38) 2208 256 ext4_ext_map_blocks+0x70b/0x1010 [ 1065.604404] kworker/-5766 0d..2 1071625999us : stack_trace_call: 39) 1952 160 ext4_map_blocks+0x325/0x530 [ 1065.604404] kworker/-5766 0d..2 1071625999us : stack_trace_call: 40) 1792 384 ext4_writepages+0x6d1/0xce0 [ 1065.604404] kworker/-5766 0d..2 1071625999us : stack_trace_call: 41) 1408 16 do_writepages+0x23/0x40 [ 1065.604404] kworker/-5766 0d..2 1071625999us : stack_trace_call: 42) 1392 96 __writeback_single_inode+0x45/0x2e0 [ 1065.604404] kworker/-5766 0d..2 1071625999us : stack_trace_call: 43) 1296 176 writeback_sb_inodes+0x2ad/0x500 [ 1065.604404] kworker/-5766 0d..2 1071626000us : stack_trace_call: 44) 1120 80 __writeback_inodes_wb+0x9e/0xd0 [ 1065.604404] kworker/-5766 0d..2 1071626000us : stack_trace_call: 45) 1040 160 wb_writeback+0x29b/0x350 [ 1065.604404] kworker/-5766 0d..2 1071626000us : stack_trace_call: 46) 880 208 bdi_writeback_workfn+0x11c/0x480 [ 1065.604404] kworker/-5766 0d..2 1071626000us : stack_trace_call: 47) 672 144 process_one_work+0x1d2/0x570 [ 1065.604404] kworker/-5766 0d..2 1071626000us : stack_trace_call: 48) 528 112 worker_thread+0x116/0x370 [ 1065.604404] kworker/-5766 0d..2 1071626001us : stack_trace_call: 49) 416 240 kthread+0xf3/0x110 [ 1065.604404] kworker/-5766 0d..2 1071626001us : stack_trace_call: 50) 176 176 ret_from_fork+0x7c/0xb0 Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- arch/x86/include/asm/page_64_types.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 8de6d9cf3b95..678205195ae1 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)) -- 1.9.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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