Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261597AbUCNTtP (ORCPT ); Sun, 14 Mar 2004 14:49:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261821AbUCNTtP (ORCPT ); Sun, 14 Mar 2004 14:49:15 -0500 Received: from hera.kernel.org ([63.209.29.2]:57251 "EHLO hera.kernel.org") by vger.kernel.org with ESMTP id S261597AbUCNTtJ (ORCPT ); Sun, 14 Mar 2004 14:49:09 -0500 Date: Sun, 14 Mar 2004 16:47:39 -0300 (BRT) From: Marcelo Tosatti X-X-Sender: marcelo@dmt.cyclades To: j-nomura@ce.jp.nec.com cc: linux-kernel@vger.kernel.org, , , , Subject: Re: [2.4] heavy-load under swap space shortage In-Reply-To: <20040310.195707.521627048.nomura@linux.bs1.fc.nec.co.jp> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6038 Lines: 163 Hi kernel colleagues, At first I was skeptic to the inclusion of this patch in v2.4 (due to the freeze), but after thinking a bit more about I have a few points in favour of this modification (read Nomura's message below and the patch to know what I'm talking about): - It is off by default - It is very simple (non intrusive), it just changes the point in which anonymous pages are inserted into the LRU. - When turned on, I dont see it being a reason for introducing new bugs. What you think of this? On Wed, 10 Mar 2004 j-nomura@ce.jp.nec.com wrote: > 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. --- 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, - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/