Messages in this thread Patch in this message | | | Date | Sat, 14 Nov 2009 03:00:57 +0900 (JST) | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 5/5] vmscan: Take order into consideration when deciding if kswapd is in trouble |
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> This makes a lot of sense. Tests look good and I added stats to make sure > the logic was triggering. On X86, kswapd avoided a congestion_wait 11723 > times and X86-64 avoided it 5084 times. I think we should hold onto the > stats temporarily until all these bugs are ironed out. > > Would you like to sign off the following? > > If you are ok to sign off, this patch should replace my patch 5 in > the series.
I'm sorry, I found my bug. Please see below.
> > ==== CUT HERE ==== > > vmscan: Stop kswapd waiting on congestion when the min watermark is not being met > > If reclaim fails to make sufficient progress, the priority is raised. > Once the priority is higher, kswapd starts waiting on congestion. However, > if the zone is below the min watermark then kswapd needs to continue working > without delay as there is a danger of an increased rate of GFP_ATOMIC > allocation failure. > > This patch changes the conditions under which kswapd waits on > congestion by only going to sleep if the min watermarks are being met. > > [mel@csn.ul.ie: Add stats to track how relevant the logic is] > Needs-signed-off-by-original-author > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > index 9716003..7d66695 100644 > --- a/include/linux/vmstat.h > +++ b/include/linux/vmstat.h > @@ -41,6 +41,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, > #endif > PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL, > KSWAPD_PREMATURE_FAST, KSWAPD_PREMATURE_SLOW, > + KSWAPD_NO_CONGESTION_WAIT, > PAGEOUTRUN, ALLOCSTALL, PGROTATED, > #ifdef CONFIG_HUGETLB_PAGE > HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL, > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ffa1766..70967e1 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1966,6 +1966,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order) > * free_pages == high_wmark_pages(zone). > */ > int temp_priority[MAX_NR_ZONES]; > + int has_under_min_watermark_zone = 0;
This is wrong declaration place. It must change to
for (priority = DEF_PRIORITY; priority >= 0; priority--) { int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ unsigned long lru_pages = 0; + int has_under_min_watermark_zone = 0;
because, has_under_min_watermark_zone should be initialized every priority.
> loop_again: > total_scanned = 0; > @@ -2085,6 +2086,15 @@ loop_again: > if (total_scanned > SWAP_CLUSTER_MAX * 2 && > total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) > sc.may_writepage = 1; > + > + /* > + * We are still under min water mark. it mean we have > + * GFP_ATOMIC allocation failure risk. Hurry up! > + */ > + if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), > + end_zone, 0)) > + has_under_min_watermark_zone = 1; > + > } > if (all_zones_ok) > break; /* kswapd: all done */ > @@ -2092,8 +2102,13 @@ loop_again: > * OK, kswapd is getting into trouble. Take a nap, then take > * another pass across the zones. > */ > - if (total_scanned && priority < DEF_PRIORITY - 2) > - congestion_wait(BLK_RW_ASYNC, HZ/10); > + if (total_scanned && (priority < DEF_PRIORITY - 2)) { > +
This blank line is unnecesary.
> + if (!has_under_min_watermark_zone)
Probably "if (has_under_min_watermark_zone)" is correct.
> + count_vm_event(KSWAPD_NO_CONGESTION_WAIT); > + else > + congestion_wait(BLK_RW_ASYNC, HZ/10); > + }
Otherthing looks pretty good to me. please feel free to add my s-o-b or reviewed-by.
Thanks.
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