From: Michal Hocko <mhocko@suse.com>
To: Feng Tang <feng.tang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>, Tejun Heo <tj@kernel.org>,
Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] mm/page_alloc: detect allocation forbidden by cpuset and bail out early
Date: Fri, 24 Sep 2021 09:17:49 +0200 [thread overview]
Message-ID: <YU17nUx+yE8ie38s@dhcp22.suse.cz> (raw)
In-Reply-To: <20210924061054.GA72911@shbuild999.sh.intel.com>
On Fri 24-09-21 14:10:54, Feng Tang wrote:
> Hi Michal,
>
> On Tue, Sep 14, 2021 at 10:50:42AM +0200, Michal Hocko wrote:
> > On Tue 14-09-21 11:40:28, Feng Tang wrote:
> [SPIN]
> > > The OOM killer cannot help to resolve the situation as there is no
> > > usable memory for the request in the cpuset scope. The only reasonable
> > > measure to take is to fail the allocation right away and have the caller
> > > to deal with it.
> > >
> > > So add a check for cases like this in the slowpath of allocation, and
> > > bail out early returning NULL for the allocation.
> > >
> > > As page allocation is one of the hottest path in kernel, this check
> > > will hurt all users with sane cpuset configuration, add a static branch
> > > check and detect the abnormal config in cpuset memory binding setup so
> > > that the extra check in page allocation is not paid by everyone.
> > >
> > > [thanks to Micho Hocko and David Rientjes for suggesting not handle
> > > it inside OOM code, adding cpuset check, refining comments]
> > >
> > > Suggested-by: Michal Hocko <mhocko@suse.com>
> > > Signed-off-by: Feng Tang <feng.tang@intel.com>
> >
> > Acked-by: Michal Hocko <mhocko@suse.com>
>
> Thank you!
>
> > Minor nit below
> > [...]
> > > +/* Whether the 'nodes' are all movable nodes */
> > > +static inline bool movable_only_nodes(nodemask_t *nodes)
> > > +{
> > > + struct zonelist *zonelist;
> > > + struct zoneref *z;
> > > +
> > > + if (nodes_empty(*nodes))
> > > + return false;
> > > +
> > > + zonelist =
> > > + &NODE_DATA(first_node(*nodes))->node_zonelists[ZONELIST_FALLBACK];
> > > + z = first_zones_zonelist(zonelist, ZONE_NORMAL, nodes);
> > > + return (!z->zone) ? true : false;
> >
> > This would read easier to me
> > /*
> > * We can chose arbitrary node from the nodemask to get a
> > * zonelist as they are interlinked. We just need to find
> > * at least one zone that can satisfy kernel allocations.
> > */
> > node = NODE_DATA(first_node(*nodes));
> > zonelist = node_zonelist(node, GFP_KERNEL);
> > z = first_zones_zonelist(zonelist, ZONE_NORMAL, nodes);
>
> When working on the v4 patch, I see some compile warning
> that 'node_zonelist()' and 'GFP_KERNEL' are either implicit
> or undeclared, as they are from "gfp.h".
>
> So we may need to move this function to gfp.h or keep the
> current code with slight modification?
>
> nid = first_node(*nodes);
> zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
> z = first_zones_zonelist(zonelist, ZONE_NORMAL, nodes);
> return (!z->zone) ? true : false;
I would put it into gfp.h but I can see how this might be not really
loved there. Both ways work with me.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-09-24 7:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-14 3:40 [PATCH v3] mm/page_alloc: detect allocation forbidden by cpuset and bail out early Feng Tang
2021-09-14 8:01 ` Vlastimil Babka
2021-09-14 8:17 ` Michal Hocko
2021-09-14 8:50 ` Michal Hocko
2021-09-24 6:10 ` Feng Tang
2021-09-24 7:17 ` Michal Hocko [this message]
2021-09-15 0:30 ` David Rientjes
2021-09-15 5:32 ` Feng Tang
2021-09-15 11:30 ` Michal Hocko
2021-09-16 8:11 ` Feng Tang
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