On Wed, Feb 26, 2014 at 03:13:33PM -0500, Johannes Weiner wrote: > On Wed, Feb 26, 2014 at 12:12:06PM -0500, Johannes Weiner wrote: > > On Wed, Feb 26, 2014 at 09:54:22AM +0000, Mel Gorman wrote: > > > How about special casing the (alloc_flags & ALLOC_WMARK_LOW) check in > > > get_page_from_freelist to also ignore GFP_THISNODE? The NR_ALLOC_BATCH > > > will go further negative if there are storms of GFP_THISNODE allocations > > > forcing other allocations into the slow path doing multiple calls to > > > prepare_slowpath but it would be closer to current behaviour and avoid > > > weirdness with kswapd. > > > > I think the result would be much uglier. The allocations wouldn't > > participate in the fairness protocol, and they'd create work for > > kswapd without waking it up, diminishing the latency reduction for > > which we have kswapd in the first place. > > > > If kswapd wakeups should be too aggressive, I'd rather we ratelimit > > them in some way rather than exempting random order-0 allocation types > > as a moderation measure. Exempting higher order wakeups, like THP > > does is one thing, but we want order-0 watermarks to be met at all > > times anyway, so it would make sense to me to nudge kswapd for every > > failing order-0 request. > > So I'd still like to fix this and wake kswapd even for GFP_THISNODE > allocations, but let's defer it for now in favor of a minimal bugfix > that can be ported to -stable. > > Would this be an acceptable replacement for 1/2? > > --- > > From: Johannes Weiner <[email protected]> > Subject: [patch 1/2] mm: page_alloc: exempt GFP_THISNODE allocations from zone > fairness > > Jan Stancek reports manual page migration encountering allocation > failures after some pages when there is still plenty of memory free, > and bisected the problem down to 81c0a2bb515f ("mm: page_alloc: fair > zone allocator policy"). > > The problem is that GFP_THISNODE obeys the zone fairness allocation > batches on one hand, but doesn't reset them and wake kswapd on the > other hand. After a few of those allocations, the batches are > exhausted and the allocations fail. > > Fixing this means either having GFP_THISNODE wake up kswapd, or > GFP_THISNODE not participating in zone fairness at all. The latter > seems safer as an acute bugfix, we can clean up later. > > Reported-by: Jan Stancek <[email protected]> > Signed-off-by: Johannes Weiner <[email protected]> > Cc: <[email protected]> # 3.12+
Acked-by: Mel Gorman <[email protected]> -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
