linux-kernel - Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20100910115503.C95E.A69D9226@jp.fujitsu.com>
Date:	Fri, 10 Sep 2010 11:56:59 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com, Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails

> On Thu, Sep 09, 2010 at 09:32:52AM -0500, Christoph Lameter wrote:
> > On Thu, 9 Sep 2010, Mel Gorman wrote:
> > 
> > > > This will have the effect of never sending IPIs for slab allocations since
> > > > they do not do allocations for orders > PAGE_ALLOC_COSTLY_ORDER.
> > > >
> > >
> > > The question is how severe is that? There is somewhat of an expectation
> > > that the lower orders free naturally so it the IPI justified? That said,
> > > our historical behaviour would have looked like
> > >
> > > if (!page && !drained && order) {
> > > 	drain_all_pages();
> > > 	draiained = true;
> > > 	goto retry;
> > > }
> > >
> > > Play it safe for now and go with that?
> > 
> > I am fine with no IPIs for order <= COSTLY. Just be aware that this is
> > a change that may have some side effects.
> 
> I made the choice consciously. I felt that if slab or slub were depending on
> IPIs to make successful allocations in low-memory conditions that it would
> experience varying stalls on bigger machines due to increased interrupts that
> might be difficult to diagnose while not necessarily improving allocation
> success rates. I also considered that if the machine is under pressure then
> slab and slub may also be releasing pages of the same order and effectively
> recycling their pages without depending on IPIs.

+1.

In these days, average numbers of CPUs are increasing. So we need to be afraid
IPI storm than past.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/