Messages in this thread Patch in this message | | | Date | Wed, 10 Mar 2004 19:57:07 +0900 (JST) | Subject | Re: [2.4] heavy-load under swap space shortage | From | j-nomura@ce ... |
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After discussion with Hugh and recommendation from Andrea, it turns out that Andrea's 05_vm_22_vm-anon-lru-3 in 2.4.23aa2 solves the problem. ftp://ftp.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.23aa2/05_vm_22_vm-anon-lru-3
The patch adds a sysctl which accelerate the performance on huge memory machine. It doesn't affect anything if turned off.
Marcelo, could you apply this to 2.4.26-pre? (I attached the slightly modified patch in which the feature is turned off by default and which is cleanly applied to bk tree.)
My test case was: - there is a process with large anonymous mapping - there are large amount of page caches and active I/O processes - there are not much of file mappings
So the problem happens in this way: - shrink_cache tries scanning inactive list in which most of pages are anonymous mapped - it soon fall into swap_out because of too many anonymous pages - when no free swap space, it hardly frees anything - it retries again but soon calls swap_out again and again
Without the patch, snapshot of readprofile looks like: 3590781 total 3289271 swap_out 212029 smp_call_function 22598 shrink_cache 21833 lru_cache_add 7787 get_user_pages
Most of the time was spent in swap_out. (contention on pagetable_lock)
After applying the patch, the snapshot is like: 17420 total 3929 copy_page 3677 statm_pgd_range 1317 try_to_free_buffers 1312 __copy_user 593 scsi_make_request
Best regards. -- NOMURA, Jun'ichi <j-nomura@ce.jp.nec.com> --- linux/include/linux/swap.h 2004/02/19 04:12:39 1.1.1.26 +++ linux/include/linux/swap.h 2004/03/10 10:09:11 @@ -116,7 +116,7 @@ extern void swap_setup(void); extern wait_queue_head_t kswapd_wait; extern int FASTCALL(try_to_free_pages_zone(zone_t *, unsigned int)); extern int FASTCALL(try_to_free_pages(unsigned int)); -extern int vm_vfs_scan_ratio, vm_cache_scan_ratio, vm_lru_balance_ratio, vm_passes, vm_gfp_debug, vm_mapped_ratio; +extern int vm_vfs_scan_ratio, vm_cache_scan_ratio, vm_lru_balance_ratio, vm_passes, vm_gfp_debug, vm_mapped_ratio, vm_anon_lru; /* linux/mm/page_io.c */ extern void rw_swap_page(int, struct page *); --- linux/include/linux/sysctl.h 2004/02/19 04:12:39 1.1.1.23 +++ linux/include/linux/sysctl.h 2004/03/10 10:09:11 @@ -156,6 +156,7 @@ enum VM_MAPPED_RATIO=20, /* amount of unfreeable pages that triggers swapout */ VM_LAPTOP_MODE=21, /* kernel in laptop flush mode */ VM_BLOCK_DUMP=22, /* dump fs activity to log */ + VM_ANON_LRU=23, /* immediatly insert anon pages in the vm page lru */ }; --- linux/kernel/sysctl.c 2003/12/02 04:48:47 1.1.1.22 +++ linux/kernel/sysctl.c 2004/03/10 10:09:12 @@ -287,6 +287,8 @@ static ctl_table vm_table[] = { &vm_cache_scan_ratio, sizeof(int), 0644, NULL, &proc_dointvec}, {VM_MAPPED_RATIO, "vm_mapped_ratio", &vm_mapped_ratio, sizeof(int), 0644, NULL, &proc_dointvec}, + {VM_ANON_LRU, "vm_anon_lru", + &vm_anon_lru, sizeof(int), 0644, NULL, &proc_dointvec}, {VM_LRU_BALANCE_RATIO, "vm_lru_balance_ratio", &vm_lru_balance_ratio, sizeof(int), 0644, NULL, &proc_dointvec}, {VM_PASSES, "vm_passes", --- linux/mm/memory.c 2003/12/02 04:48:47 1.1.1.31 +++ linux/mm/memory.c 2004/03/10 10:09:12 @@ -984,7 +984,8 @@ static int do_wp_page(struct mm_struct * if (PageReserved(old_page)) ++mm->rss; break_cow(vma, new_page, address, page_table); - lru_cache_add(new_page); + if (vm_anon_lru) + lru_cache_add(new_page); /* Free the old page.. */ new_page = old_page; @@ -1215,7 +1216,8 @@ static int do_anonymous_page(struct mm_s mm->rss++; flush_page_to_ram(page); entry = pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot))); - lru_cache_add(page); + if (vm_anon_lru) + lru_cache_add(page); mark_page_accessed(page); } @@ -1270,7 +1272,8 @@ static int do_no_page(struct mm_struct * } copy_user_highpage(page, new_page, address); page_cache_release(new_page); - lru_cache_add(page); + if (vm_anon_lru) + lru_cache_add(page); new_page = page; } --- linux/mm/vmscan.c 2004/02/19 04:12:33 1.1.1.32 +++ linux/mm/vmscan.c 2004/03/10 10:09:13 @@ -65,6 +65,27 @@ int vm_lru_balance_ratio = 2; int vm_vfs_scan_ratio = 6; /* + * "vm_anon_lru" select if to immdiatly insert anon pages in the + * lru. Immediatly means as soon as they're allocated during the + * page faults. + * + * If this is set to 0, they're inserted only after the first + * swapout. + * + * Having anon pages immediatly inserted in the lru allows the + * VM to know better when it's worthwhile to start swapping + * anonymous ram, it will start to swap earlier and it should + * swap smoother and faster, but it will decrease scalability + * on the >16-ways of an order of magnitude. Big SMP/NUMA + * definitely can't take an hit on a global spinlock at + * every anon page allocation. So this is off by default. + * + * Low ram machines that swaps all the time want to turn + * this on (i.e. set to 1). + */ +int vm_anon_lru = 1; + +/* * The swap-out function returns 1 if it successfully * scanned all the pages it was asked to (`count'). * It returns zero if it couldn't do anything, | |