From: David Rientjes <rientjes@google.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
mhocko@kernel.org, ying.huang@intel.com, s.priebe@profihost.ag,
mgorman@techsingularity.net,
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, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression
Date: Mon, 3 Dec 2018 12:36:09 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.21.1812031226510.192288@chino.kir.corp.google.com> (raw)
In-Reply-To: <20181203201214.GB3540@redhat.com>
On Mon, 3 Dec 2018, Andrea Arcangeli wrote:
> In my earlier review of David's patch, it looked runtime equivalent to
> the __GFP_COMPACT_ONLY solution. It has the only advantage of adding a
> new gfpflag until we're sure we need it but it's the worst solution
> available for the long term in my view. It'd be ok to apply it as
> stop-gap measure though.
>
> The "order == pageblock_order" hardcoding inside the allocator to
> workaround the __GFP_THISNODE flag passed from outside the allocator
> in the THP MADV_HUGEPAGE case, didn't look very attractive because
> it's not just THP allocating order >0 pages.
>
We have two different things to consider: NUMA locality and the order of
the allocation. THP is preferred locally and we know the order. For the
other high-order pages you're referring to, I don't know if they are using
__GFP_THISNODE or not (likely not). I see them as two separate issues.
For thp on all platforms I have measured it on specifically for this patch
(Broadwell, Haswell, Rome) there is a clear advantage to faulting local
pages of the native page size over remote hugepages. It also has the
added effect of allowing khugepaged to collapse it into a hugepage later
if fragmentation allows (the reason why khugepaged cares about NUMA
locality, the same reason I do). This is the rationale for __GFP_THISNODE
for thp allocations.
For order == pageblock_order (or more correctly order >= pageblock_order),
this is not based on NUMA whatsoever but is rather based on the
implementation of memory compaction. If it has already failed (or was
deferred for order-HPAGE_PMD_ORDER), reclaim cannot be shown to help if
memory compaction cannot utilize the freed memory in isolate_freepages(),
so that reclaim has been pointless. If compaction fails for other reasons
(any unmovable page preventing a pageblock from becoming free), *all*
reclaim activity has been pointless.
> It'd be nicer if whatever compaction latency optimization that applies
> to THP could also apply to all other allocation orders too and the
> hardcoding of the THP order prevents that.
>
> On the same lines if __GFP_THISNODE is so badly needed by
> MADV_HUGEPAGE, all other larger order allocations should also be able
> to take advantage of __GFP_THISNODE without ending in the same VM
> corner cases that required the "order == pageblock_order" hardcoding
> inside the allocator.
>
> If you prefer David's patch I would suggest pageblock_order to be
> replaced with HPAGE_PMD_ORDER so it's more likely to match the THP
> order in all archs.
>
That sounds fine and I will do that in my v2.
next prev parent reply other threads:[~2018-12-03 20:36 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 [this message]
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
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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