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  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 11 Aug 2014 14:05:18 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
cc:	Li Zefan <lizefan@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH -mm] slab: fix cpuset check in fallback_alloc

On Mon, 11 Aug 2014, Vladimir Davydov wrote:

> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1963,7 +1963,7 @@ zonelist_scan:
> >  
> >  	/*
> >  	 * Scan zonelist, looking for a zone with enough free.
> > -	 * See also __cpuset_node_allowed_softwall() comment in kernel/cpuset.c.
> > +	 * See __cpuset_node_allowed() comment in kernel/cpuset.c.
> >  	 */
> >  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> >  						high_zoneidx, nodemask) {
> > @@ -1974,7 +1974,7 @@ zonelist_scan:
> >  				continue;
> >  		if (cpusets_enabled() &&
> >  			(alloc_flags & ALLOC_CPUSET) &&
> > -			!cpuset_zone_allowed_softwall(zone, gfp_mask))
> > +			!cpuset_zone_allowed(zone, gfp_mask))
> >  				continue;
> 
> So, this is get_page_from_freelist. It's called from
> __alloc_pages_nodemask with alloc_flags always having ALLOC_CPUSET bit
> set and from __alloc_pages_slowpath with alloc_flags having ALLOC_CPUSET
> bit set only for __GFP_WAIT allocations. That said, w/o your patch we
> try to respect cpusets for all allocations, including atomic, and only
> ignore cpusets if tight on memory (freelist's empty) for !__GFP_WAIT
> allocations, while with your patch we always ignore cpusets for
> !__GFP_WAIT allocations. Not sure if it really matters though, because
> usually one uses cpuset.mems in conjunction with cpuset.cpus and it
> won't make any difference then. It also doesn't conflict with any cpuset
> documentation.
> 

Yeah, that's why I'm asking Li, the cpuset maintainer, if we can do this.  
The only thing that we get by falling back to the page allocator slowpath 
is that kswapd gets woken up before the allocation is attempted without 
ALLOC_CPUSET.  It seems pointless to wakeup kswapd when the allocation can 
succeed on any node.  Even with the patch, if the allocation fails because 
all nodes are below their min watermark, then we still fallback to the 
slowpath and wake up kswapd but there's nothing much else we can do 
because it's !__GFP_WAIT.
--
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/

Powered by blists - more mailing lists