On Thu, Jan 27, 2011 at 01:40:58PM +0000, Mel Gorman wrote: > On Wed, Jan 26, 2011 at 05:42:37PM +0000, Mel Gorman wrote: > > On Wed, Jan 26, 2011 at 04:36:55PM +0000, Mel Gorman wrote: > > > > But the wmarks don't > > > > seem the real offender, maybe it's something related to the tiny pci32 > > > > zone that materialize on 4g systems that relocate some little memory > > > > over 4g to make space for the pci32 mmio. I didn't yet finish to debug > > > > it. > > > > > > > > > > This has to be it. What I think is happening is that we're in balance_pgdat(), > > > the "Normal" zone is never hitting the watermark and we constantly call > > > "goto loop_again" trying to "rebalance" all zones. > > > > > > > Confirmed. > > <SNIP> > > How about the following? Functionally it would work but I am concerned > that the logic in balance_pgdat() and kswapd() is getting out of hand > having being adjusted to work with a number of corner cases already. In > the next cycle, it could do with a "do-over" attempt to make it easier > to follow. That number 8 is the problem, I don't think anybody was ever supposed to free 8*highwmark pages. kswapd must work in the hysteresis range low->high area and then sleep wait low to hit again before it gets wakenup. Not sure how that number 8 ever come up... but to be it looks like the real offender and I wouldn't work around it. totally untested... I will test.... ==== Subject: vmscan: kswapd must not free more than high_wmark pages From: Andrea Arcangeli <aarcange@xxxxxxxxxx> When the min_free_kbytes is set with `hugeadm --set-recommended-min_free_kbytes" or with THP enabled (which runs the equivalent of "hugeadm --set-recommended-min_free_kbytes" to activate anti-frag at full effectiveness automatically at boot) the high wmark of some zone is as high as ~88M. 88M free on a 4G system isn't horrible, but 88M*8 = 704M free on a 4G system is definitely unbearable. This only tends to be visible on 4G systems with tiny over-4g zone where kswapd insists to reach the high wmark on the over-4g zone but doing so it shrunk up to 704M from the normal zone by mistake. Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> --- diff --git a/mm/vmscan.c b/mm/vmscan.c index f5d90de..9e3c78e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2407,7 +2407,7 @@ loop_again: * zone has way too many pages free already. */ if (!zone_watermark_ok_safe(zone, order, - 8*high_wmark_pages(zone), end_zone, 0)) + high_wmark_pages(zone), end_zone, 0)) shrink_zone(priority, zone, &sc); reclaim_state->reclaimed_slab = 0; nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>