Messages in this thread | | | Date | Wed, 26 May 2004 09:41:04 -0300 | From | Marcelo Tosatti <> | Subject | Re: [2.4] heavy-load under swap space shortage |
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Andrea, Hugh, Jun'ichi,
I think we can merge this patch.
Its very safe - default behaviour unchanged.
Jun, are you willing to do another test for us if this gets merged in v2.4.27-pre4 ?
Maybe we should document the VM tunables somewhere outside source code (Documentation/) ?
On Wed, Mar 10, 2004 at 07:57:07PM +0900, 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. > -- > 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,
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