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From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.com>,
	David Hildenbrand <david@redhat.com>,
	Oscar Salvador <osalvador@suse.de>,
	Dan Williams <dan.j.williams@intel.com>,
	Sasha Levin <sashal@kernel.org>,
	Tyler Hicks <tyhicks@linux.microsoft.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	mike.kravetz@oracle.com, Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Mel Gorman <mgorman@suse.de>,
	Matthew Wilcox <willy@infradead.org>,
	David Rientjes <rientjes@google.com>,
	John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 6/6] mm/gup: migrate pinned pages out of movable zone
Date: Fri, 4 Dec 2020 11:24:56 -0500	[thread overview]
Message-ID: <CA+CK2bA18wXtETPpz4eeX02oagg1fyW=yNuN4UZVpBW0V4A1CQ@mail.gmail.com> (raw)
In-Reply-To: <20201203193607.GV5487@ziepe.ca>

On Thu, Dec 3, 2020 at 2:36 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Thu, Dec 03, 2020 at 02:15:36PM -0500, Pavel Tatashin wrote:
>
> > I studied some more, and I think this is not a race:
> > list_add_tail(&head->lru, &cma_page_list) is called only when
> > isolate_lru_page(head) succeeds.
> > isolate_lru_page(head) succeeds only when PageLRU(head) is true.
> > However, in this function we also clear LRU flag before returning
> > success.
> > This means, that if we race with another thread, the other thread
> > won't get to unprotected list_add_tail(&head->lru, &cma_page_list)
> > until head is is back on LRU list.
>
> Oh interesting, I totally didn't see how that LRU stuff is
> working. So.. this creates a ridiculously expensive spin lock? Not
> broken, but yikes :|

Not really a spin lock, the second thread won't be able to isolate
this page, and will skip migration of this page.

>
> Jason

  reply	other threads:[~2020-12-04 16:26 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-02  5:23 [PATCH 0/6] prohibit pinning pages in ZONE_MOVABLE Pavel Tatashin
2020-12-02  5:23 ` [PATCH 1/6] mm/gup: perform check_dax_vmas only when FS_DAX is enabled Pavel Tatashin
2020-12-02 16:22   ` Ira Weiny
2020-12-02 18:15     ` Pavel Tatashin
2020-12-02 18:15       ` Pavel Tatashin
2020-12-02 16:29   ` Jason Gunthorpe
2020-12-02 18:16     ` Pavel Tatashin
2020-12-02 18:16       ` Pavel Tatashin
2020-12-03  7:59   ` John Hubbard
2020-12-03 14:52     ` Pavel Tatashin
2020-12-03 14:52       ` Pavel Tatashin
2020-12-02  5:23 ` [PATCH 2/6] mm/gup: don't pin migrated cma pages in movable zone Pavel Tatashin
2020-12-02 16:31   ` David Hildenbrand
2020-12-02 18:17     ` Pavel Tatashin
2020-12-02 18:17       ` Pavel Tatashin
2020-12-03  8:01   ` John Hubbard
2020-12-03  8:46   ` Michal Hocko
2020-12-03 14:58     ` Pavel Tatashin
2020-12-03 14:58       ` Pavel Tatashin
2020-12-02  5:23 ` [PATCH 3/6] mm/gup: make __gup_longterm_locked common Pavel Tatashin
2020-12-02 16:31   ` Ira Weiny
2020-12-02 16:33     ` Ira Weiny
2020-12-02 18:19       ` Pavel Tatashin
2020-12-02 18:19         ` Pavel Tatashin
2020-12-03  0:03         ` Pavel Tatashin
2020-12-03  0:03           ` Pavel Tatashin
2020-12-03  8:03   ` John Hubbard
2020-12-03 15:02     ` Pavel Tatashin
2020-12-03 15:02       ` Pavel Tatashin
2020-12-02  5:23 ` [PATCH 4/6] mm cma: rename PF_MEMALLOC_NOCMA to PF_MEMALLOC_NOMOVABLE Pavel Tatashin
2020-12-03  8:04   ` John Hubbard
2020-12-03 15:02     ` Pavel Tatashin
2020-12-03 15:02       ` Pavel Tatashin
2020-12-03  8:57   ` Michal Hocko
2020-12-03 15:02     ` Pavel Tatashin
2020-12-03 15:02       ` Pavel Tatashin
2020-12-02  5:23 ` [PATCH 5/6] mm: honor PF_MEMALLOC_NOMOVABLE for all allocations Pavel Tatashin
2020-12-03  8:17   ` John Hubbard
2020-12-03 15:06     ` Pavel Tatashin
2020-12-03 15:06       ` Pavel Tatashin
2020-12-03 16:51       ` John Hubbard
2020-12-03  9:17   ` Michal Hocko
2020-12-03 15:15     ` Pavel Tatashin
2020-12-03 15:15       ` Pavel Tatashin
2020-12-04  8:43       ` Michal Hocko
2020-12-04  8:54         ` Michal Hocko
2020-12-04 16:07           ` Pavel Tatashin
2020-12-04 16:07             ` Pavel Tatashin
2020-12-02  5:23 ` [PATCH 6/6] mm/gup: migrate pinned pages out of movable zone Pavel Tatashin
2020-12-02 16:35   ` Jason Gunthorpe
2020-12-03  0:19     ` Pavel Tatashin
2020-12-03  0:19       ` Pavel Tatashin
2020-12-03  1:08       ` Jason Gunthorpe
2020-12-03  1:34         ` Pavel Tatashin
2020-12-03  1:34           ` Pavel Tatashin
2020-12-03 14:17           ` Jason Gunthorpe
2020-12-03 16:40             ` Pavel Tatashin
2020-12-03 16:40               ` Pavel Tatashin
2020-12-03 16:59               ` Jason Gunthorpe
2020-12-03 17:14                 ` Pavel Tatashin
2020-12-03 17:14                   ` Pavel Tatashin
2020-12-03 19:15                   ` Pavel Tatashin
2020-12-03 19:15                     ` Pavel Tatashin
2020-12-03 19:36                     ` Jason Gunthorpe
2020-12-04 16:24                       ` Pavel Tatashin [this message]
2020-12-04 16:24                         ` Pavel Tatashin
2020-12-04 17:06                         ` Jason Gunthorpe
2020-12-04 20:05             ` Daniel Jordan
2020-12-04 20:16               ` Pavel Tatashin
2020-12-04 20:16                 ` Pavel Tatashin
2020-12-08  2:27                 ` Daniel Jordan
2020-12-04 20:52               ` Jason Gunthorpe
2020-12-08  2:48                 ` Daniel Jordan
2020-12-08 13:24                   ` Jason Gunthorpe
2020-12-03  8:22   ` John Hubbard
2020-12-03 15:55     ` Pavel Tatashin
2020-12-03 15:55       ` Pavel Tatashin
2020-12-04  4:13   ` Joonsoo Kim
2020-12-04 17:43     ` Pavel Tatashin
2020-12-04 17:43       ` Pavel Tatashin
2020-12-07  7:13       ` Joonsoo Kim
2020-12-04  4:02 ` [PATCH 0/6] prohibit pinning pages in ZONE_MOVABLE Joonsoo Kim
2020-12-04 15:55   ` Pavel Tatashin
2020-12-04 15:55     ` Pavel Tatashin
2020-12-04 16:10     ` Jason Gunthorpe
2020-12-04 17:50       ` Pavel Tatashin
2020-12-04 17:50         ` Pavel Tatashin
2020-12-04 18:01         ` David Hildenbrand
2020-12-04 18:10           ` Pavel Tatashin
2020-12-04 18:10             ` Pavel Tatashin
2020-12-07  7:12         ` Joonsoo Kim
2020-12-07 12:13           ` Michal Hocko

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