From: Michal Hocko <mhocko@kernel.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
ying.huang@intel.com, s.priebe@profihost.ag,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
alex.williamson@redhat.com, lkp@01.org, kirill@shutemov.name,
Andrew Morton <akpm@linux-foundation.org>,
zi.yan@cs.rutgers.edu
Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression
Date: Wed, 5 Dec 2018 12:43:53 +0100 [thread overview]
Message-ID: <20181205114353.GH1286@dhcp22.suse.cz> (raw)
In-Reply-To: <20181205104343.GZ23260@techsingularity.net>
On Wed 05-12-18 10:43:43, Mel Gorman wrote:
> On Wed, Dec 05, 2018 at 10:08:56AM +0100, Michal Hocko wrote:
> > On Tue 04-12-18 16:47:23, David Rientjes wrote:
> > > On Tue, 4 Dec 2018, Mel Gorman wrote:
> > >
> > > > What should also be kept in mind is that we should avoid conflating
> > > > locality preferences with THP preferences which is separate from THP
> > > > allocation latencies. The whole __GFP_THISNODE approach is pushing too
> > > > hard on locality versus huge pages when MADV_HUGEPAGE or always-defrag
> > > > are used which is very unfortunate given that MADV_HUGEPAGE in itself says
> > > > nothing about locality -- that is the business of other madvise flags or
> > > > a specific policy.
> > >
> > > We currently lack those other madvise modes or mempolicies: mbind() is not
> > > a viable alternative because we do not want to oom kill when local memory
> > > is depleted, we want to fallback to remote memory.
> >
> > Yes, there was a clear agreement that there is no suitable mempolicy
> > right now and there were proposals to introduce MPOL_NODE_RECLAIM to
> > introduce that behavior. This would be an improvement regardless of THP
> > because global node-reclaim policy was simply a disaster we had to turn
> > off by default and the global semantic was a reason people just gave up
> > using it completely.
> >
>
> The alternative is to define a clear semantic for THP allocation
> requests that are considered "light" regardless of whether that needs a
> GFP flag or not. A sensible default might be
>
> o Allocate THP local if the amount of work is light or non-existant.
> o Allocate THP remote if one is freely available with no additional work
> (maybe kick remote kcompactd)
> o Allocate base page local if the amount of work is light or non-existant
> o Allocate base page remote if the amount of work is light or non-existant
> o Do heavy work in zonelist order until a base page is allocated somewhere
I am not sure about the ordering without a deeper consideration but I
thin THP should reflect the approach we have for base bages.
> It's not something could be clearly expressed with either NORETRY or
> THISNODE but longer-term might be saner than chopping and changing on
> which flags are more important and which workload is most relevant. That
> runs the risk of a revert-loop where each person targetting one workload
> reverts one patch to insert another until someone throws up their hands
> in frustration and just carries patches out-of-tree long-term.
Fully agreed!
> I'm not going to prototype something along these lines for now as
> fundamentally a better compaction could cut out part of the root cause
> of pain.
Yes there is some ground work to be done first.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-12-05 11:43 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 6:25 [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression kernel test robot
2018-11-27 17:08 ` Linus Torvalds
2018-11-27 18:17 ` Michal Hocko
2018-11-27 18:21 ` Michal Hocko
2018-11-27 19:05 ` Vlastimil Babka
2018-11-27 19:16 ` Vlastimil Babka
2018-11-27 20:57 ` Andrea Arcangeli
2018-11-27 22:50 ` Linus Torvalds
2018-11-28 6:30 ` Michal Hocko
2018-11-28 3:20 ` Huang, Ying
2018-11-28 16:48 ` Linus Torvalds
2018-11-28 18:39 ` Andrea Arcangeli
2018-11-28 23:10 ` David Rientjes
2018-12-03 18:01 ` Linus Torvalds
2018-12-03 18:14 ` Michal Hocko
2018-12-03 18:19 ` Linus Torvalds
2018-12-03 18:30 ` Michal Hocko
2018-12-03 18:45 ` Linus Torvalds
2018-12-03 18:59 ` Michal Hocko
2018-12-03 19:23 ` Andrea Arcangeli
2018-12-03 20:26 ` David Rientjes
2018-12-03 19:28 ` Linus Torvalds
2018-12-03 20:12 ` Andrea Arcangeli
2018-12-03 20:36 ` David Rientjes
2018-12-03 22:04 ` Linus Torvalds
2018-12-03 22:27 ` Linus Torvalds
2018-12-03 22:57 ` David Rientjes
2018-12-04 9:22 ` Vlastimil Babka
2018-12-04 10:45 ` Mel Gorman
2018-12-05 0:47 ` David Rientjes
2018-12-05 9:08 ` Michal Hocko
2018-12-05 10:43 ` Mel Gorman
2018-12-05 11:43 ` Michal Hocko [this message]
2018-12-05 10:06 ` Mel Gorman
2018-12-05 20:40 ` Andrea Arcangeli
2018-12-05 21:59 ` David Rientjes
2018-12-06 0:00 ` Andrea Arcangeli
2018-12-05 22:03 ` Linus Torvalds
2018-12-05 22:12 ` David Rientjes
2018-12-05 23:36 ` Andrea Arcangeli
2018-12-05 23:51 ` Linus Torvalds
2018-12-06 0:58 ` Linus Torvalds
2018-12-06 9:14 ` MADV_HUGEPAGE vs. NUMA semantic (was: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression) Michal Hocko
2018-12-06 23:49 ` David Rientjes
2018-12-07 7:34 ` Michal Hocko
2018-12-07 4:31 ` Linus Torvalds
2018-12-07 7:49 ` Michal Hocko
2018-12-07 9:06 ` Vlastimil Babka
2018-12-07 23:15 ` David Rientjes
2018-12-06 23:43 ` [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression David Rientjes
2018-12-07 4:01 ` Linus Torvalds
2018-12-10 0:29 ` David Rientjes
2018-12-10 4:49 ` Andrea Arcangeli
2018-12-12 0:37 ` David Rientjes
2018-12-12 9:50 ` Michal Hocko
2018-12-12 17:00 ` Andrea Arcangeli
2018-12-14 11:32 ` Michal Hocko
2018-12-12 10:14 ` Vlastimil Babka
2018-12-14 21:04 ` David Rientjes
2018-12-14 21:33 ` Vlastimil Babka
2018-12-21 22:18 ` David Rientjes
2018-12-22 12:08 ` Mel Gorman
2018-12-14 23:11 ` Mel Gorman
2018-12-21 22:15 ` David Rientjes
2018-12-12 10:44 ` Andrea Arcangeli
2019-04-15 11:48 ` Michal Hocko
2018-12-06 0:18 ` David Rientjes
2018-12-06 0:54 ` Andrea Arcangeli
2018-12-06 9:23 ` Vlastimil Babka
2018-12-03 20:39 ` David Rientjes
2018-12-03 21:25 ` Michal Hocko
2018-12-03 21:53 ` David Rientjes
2018-12-04 8:48 ` Michal Hocko
2018-12-05 0:07 ` David Rientjes
2018-12-05 10:18 ` Michal Hocko
2018-12-05 19:16 ` David Rientjes
2018-11-27 7:23 kernel test robot
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