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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
	david@redhat.com, osalvador@suse.de, dan.j.williams@intel.com,
	sashal@kernel.org, tyhicks@linux.microsoft.com,
	iamjoonsoo.kim@lge.com, mike.kravetz@oracle.com,
	rostedt@goodmis.org, mingo@redhat.com, peterz@infradead.org,
	mgorman@suse.de, willy@infradead.org, rientjes@google.com,
	jhubbard@nvidia.com, linux-doc@vger.kernel.org,
	ira.weiny@intel.com, linux-kselftest@vger.kernel.org,
	jmorris@namei.org
Subject: Re: [PATCH v8 02/14] mm/gup: check every subpage of a compound page during isolation
Date: Wed, 3 Feb 2021 10:53:13 -0400	[thread overview]
Message-ID: <20210203145313.GQ4718@ziepe.ca> (raw)
In-Reply-To: <05a66361-214c-2afe-22e4-12862ea1e4e2@oracle.com>

On Wed, Feb 03, 2021 at 01:22:18PM +0000, Joao Martins wrote:

> With this, longterm gup will 'regress' for hugetlbfs e.g. from ~6k -> 32k usecs when
> pinning a 16G hugetlb file.

Yes, but correctness demands it.

The solution is to track these pages as we discover them so we know if
a PMD/PUD points and can directly skip the duplicated work

> Splitting can only occur on THP right? If so, perhaps we could
> retain the @step increment for compound pages but when
> !is_transparent_hugepage(head) or just PageHuge(head) like:

Honestly I'd rather see it fixed properly which will give even bigger
performance gains - avoiding the entire rescan of the page list will
be a win

Jason

  parent reply	other threads:[~2021-02-03 14:54 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-25 19:47 [PATCH v8 00/14] prohibit pinning pages in ZONE_MOVABLE Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 01/14] mm/gup: don't pin migrated cma pages in movable zone Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 02/14] mm/gup: check every subpage of a compound page during isolation Pavel Tatashin
2021-02-03 13:22   ` Joao Martins
2021-02-03 14:51     ` Pavel Tatashin
2021-02-03 15:32       ` Joao Martins
2021-02-03 16:46         ` Joao Martins
2021-02-03 14:53     ` Jason Gunthorpe [this message]
2021-02-03 16:13       ` Joao Martins
2021-02-03 18:00         ` Jason Gunthorpe
2021-01-25 19:47 ` [PATCH v8 03/14] mm/gup: return an error on migration failure Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 04/14] mm/gup: check for isolation errors Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 05/14] mm cma: rename PF_MEMALLOC_NOCMA to PF_MEMALLOC_PIN Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 06/14] mm: apply per-task gfp constraints in fast path Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 07/14] mm: honor PF_MEMALLOC_PIN for all movable pages Pavel Tatashin
     [not found]   ` <20210131130903.4875-1-lecopzer@gmail.com>
2021-01-31 16:03     ` Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 08/14] mm/gup: do not migrate zero page Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 09/14] mm/gup: migrate pinned pages out of movable zone Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 10/14] memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 11/14] mm/gup: change index type to long as it counts pages Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 12/14] mm/gup: longterm pin migration cleanup Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 13/14] selftests/vm: gup_test: fix test flag Pavel Tatashin
2021-01-25 19:47 ` [PATCH v8 14/14] selftests/vm: gup_test: test faulting in kernel, and verify pinnable pages Pavel Tatashin

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