> > Do you see my old patch? The patch want't incomplet but it's not bad for showing an idea. > > http://marc.info/?l=linux-mm&m=129187231129887&w=4 > > The idea is to keep a page at leat for direct reclaimed process. > > Could it mitigate your problem or could you enhacne the idea? > > I think it's very simple and fair solution. > > No it's not helping my problem, nr_alloc_fail and CAL are still high: > > root@fat /home/wfg# ./test-dd-sparse.sh > start time: 246 > total time: 531 > nr_alloc_fail 14097 > allocstall 1578332 > LOC: 542698 538947 536986 567118 552114 539605 541201 537623 Local timer interrupts > RES: 3368 1908 1474 1476 2809 1602 1500 1509 Rescheduling interrupts > CAL: 223844 224198 224268 224436 223952 224056 223700 223743 Function call interrupts > TLB: 381 27 22 19 96 404 111 67 TLB shootdowns > > root@fat /home/wfg# getdelays -dip `pidof dd` > print delayacct stats ON > printing IO accounting > PID 5202 > > > CPU count real total virtual total delay total > 1132 3635447328 3627947550 276722091605 > IO count delay total delay average > 2 187809974 62ms > SWAP count delay total delay average > 0 0 0ms > RECLAIM count delay total delay average > 1334 35304580824 26ms > dd: read=278528, write=0, cancelled_write=0 > > I guess your patch is mainly fixing the high order allocations while > my workload is mainly order 0 readahead page allocations. There are > 1000 forks, however the "start time: 246" seems to indicate that the > order-1 reclaim latency is not improved. > > I'll try modifying your patch and see how it works out. The obvious > change is to apply it to the order-0 case. Hope this won't create much > more isolated pages. I tried the below modified patch, removing the high order test and the drain_all_pages() call. The results are not idea either: root@fat /home/wfg# ./test-dd-sparse.sh start time: 246 total time: 526 nr_alloc_fail 15582 allocstall 1583727 LOC: 532518 528880 528184 533426 532765 530526 531177 528757 Local timer interrupts RES: 2350 1929 1538 1430 3359 1547 1422 1502 Rescheduling interrupts CAL: 200017 200384 200336 199763 200369 199776 199504 199407 Function call interrupts TLB: 285 19 24 10 121 306 113 69 TLB shootdowns CPU count real total virtual total delay total 1154 3767427264 3742671454 273770720370 IO count delay total delay average 1 279795961 279ms SWAP count delay total delay average 0 0 0ms RECLAIM count delay total delay average 1385 27228068276 19ms dd: read=12288, write=0, cancelled_write=0 Thanks, Fengguang --- Subject: Keep freed pages in direct reclaim Date: Thu, 9 Dec 2010 14:01:32 +0900 From: Minchan Kim <minchan.kim@xxxxxxxxx> direct reclaimed process often sleep and race with other processes. Although direct reclaim proceess requires high order pags(order > 0) and reclaims page successfully, other processes which require order-0 page could steal the high order page for direct reclaimed process. After all, direct reclaimed process try it again and it still has a possibility of above scenario. It can make bad effects following as 1. direct reclaimed process latency is big 2. eviction working set page due to lumpy reclaim 3. continue to wake up kswapd This patch solves it. Fengguang: fix [ 1514.892933] BUG: unable to handle kernel [ 1514.892958] ---[ end trace be7cb17861e1d25b ]--- [ 1514.893589] NULL pointer dereference at (null) [ 1514.893968] IP: [<ffffffff81101b2e>] shrink_page_list+0x3dc/0x501 Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- fs/buffer.c | 2 +- include/linux/swap.h | 4 +++- mm/page_alloc.c | 25 +++++++++++++++++++++---- mm/vmscan.c | 23 +++++++++++++++++++---- 4 files changed, 44 insertions(+), 10 deletions(-) --- linux-next.orig/fs/buffer.c 2011-05-02 17:18:01.000000000 +0800 +++ linux-next/fs/buffer.c 2011-05-02 18:30:17.000000000 +0800 @@ -289,7 +289,7 @@ static void free_more_memory(void) &zone); if (zone) try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, - GFP_NOFS, NULL); + GFP_NOFS, NULL, NULL); } } --- linux-next.orig/include/linux/swap.h 2011-05-02 17:18:01.000000000 +0800 +++ linux-next/include/linux/swap.h 2011-05-02 18:30:17.000000000 +0800 @@ -249,8 +249,10 @@ static inline void lru_cache_add_file(st #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ /* linux/mm/vmscan.c */ +extern noinline_for_stack void free_page_list(struct list_head *free_pages); extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order, - gfp_t gfp_mask, nodemask_t *mask); + gfp_t gfp_mask, nodemask_t *mask, + struct list_head *freed_pages); extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem, gfp_t gfp_mask, bool noswap, unsigned int swappiness); --- linux-next.orig/mm/page_alloc.c 2011-05-02 17:18:01.000000000 +0800 +++ linux-next/mm/page_alloc.c 2011-05-02 18:31:30.000000000 +0800 @@ -1891,6 +1891,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m struct page *page = NULL; struct reclaim_state reclaim_state; bool drained = false; + LIST_HEAD(freed_pages); cond_resched(); @@ -1901,16 +1902,31 @@ __alloc_pages_direct_reclaim(gfp_t gfp_m reclaim_state.reclaimed_slab = 0; current->reclaim_state = &reclaim_state; - *did_some_progress = try_to_free_pages(zonelist, order, gfp_mask, nodemask); - + /* + * If request is high order, keep the pages which are reclaimed + * in own list for preventing the lose by other processes. + */ + *did_some_progress = try_to_free_pages(zonelist, order, gfp_mask, + nodemask, &freed_pages); current->reclaim_state = NULL; lockdep_clear_current_reclaim_state(); current->flags &= ~PF_MEMALLOC; + if (!list_empty(&freed_pages)) { + free_page_list(&freed_pages); + /* drain_all_pages(); */ + /* drained = true; */ + page = get_page_from_freelist(gfp_mask, nodemask, order, + zonelist, high_zoneidx, + alloc_flags, preferred_zone, + migratetype); + if (page) + goto out; + } cond_resched(); if (unlikely(!(*did_some_progress))) - return NULL; + goto out; retry: page = get_page_from_freelist(gfp_mask, nodemask, order, @@ -1927,7 +1943,8 @@ retry: drained = true; goto retry; } - +out: + VM_BUG_ON(!list_empty(&freed_pages)); return page; } --- linux-next.orig/mm/vmscan.c 2011-05-02 17:18:01.000000000 +0800 +++ linux-next/mm/vmscan.c 2011-05-02 18:30:17.000000000 +0800 @@ -112,6 +112,9 @@ struct scan_control { * are scanned. */ nodemask_t *nodemask; + + /* keep freed pages */ + struct list_head *freed_pages; }; #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) @@ -681,7 +684,7 @@ static enum page_references page_check_r return PAGEREF_RECLAIM; } -static noinline_for_stack void free_page_list(struct list_head *free_pages) +noinline_for_stack void free_page_list(struct list_head *free_pages) { struct pagevec freed_pvec; struct page *page, *tmp; @@ -712,6 +715,10 @@ static unsigned long shrink_page_list(st unsigned long nr_dirty = 0; unsigned long nr_congested = 0; unsigned long nr_reclaimed = 0; + struct list_head *free_list = &free_pages; + + if (sc->freed_pages) + free_list = sc->freed_pages; cond_resched(); @@ -904,7 +911,7 @@ free_it: * Is there need to periodically free_page_list? It would * appear not as the counts should be low */ - list_add(&page->lru, &free_pages); + list_add(&page->lru, free_list); continue; cull_mlocked: @@ -940,7 +947,13 @@ keep_lumpy: if (nr_dirty == nr_congested && nr_dirty != 0) zone_set_flag(zone, ZONE_CONGESTED); - free_page_list(&free_pages); + /* + * If reclaim is direct path and high order, caller should + * free reclaimed pages. It is for preventing reclaimed pages + * lose by other processes. + */ + if (!sc->freed_pages) + free_page_list(&free_pages); list_splice(&ret_pages, page_list); count_vm_events(PGACTIVATE, pgactivate); @@ -2118,7 +2131,8 @@ out: } unsigned long try_to_free_pages(struct zonelist *zonelist, int order, - gfp_t gfp_mask, nodemask_t *nodemask) + gfp_t gfp_mask, nodemask_t *nodemask, + struct list_head *freed_pages) { unsigned long nr_reclaimed; struct scan_control sc = { @@ -2131,6 +2145,7 @@ unsigned long try_to_free_pages(struct z .order = order, .mem_cgroup = NULL, .nodemask = nodemask, + .freed_pages = freed_pages, }; trace_mm_vmscan_direct_reclaim_begin(order, -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>