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From: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
To: Yang Shi <shy828301@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Zi Yan <ziy@nvidia.com>, Michal Hocko <mhocko@suse.com>,
	Huang Ying <ying.huang@intel.com>,
	Hugh Dickins <hughd@google.com>,
	hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	linux-s390@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexander Gordeev <agordeev@linux.ibm.com>
Subject: Re: [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA hinting fault
Date: Tue, 6 Apr 2021 14:02:51 +0200	[thread overview]
Message-ID: <20210406140251.2779c400@thinkpad> (raw)
In-Reply-To: <CAHbLzkquYxq_eXoVhUCib9qu_aMS9U2XXjb5pop9JtJ8uco_vg@mail.gmail.com>

On Thu, 1 Apr 2021 13:10:49 -0700
Yang Shi <shy828301@gmail.com> wrote:

[...]
> > >
> > > Yes, it could be. The old behavior of migration was to return -ENOMEM
> > > if THP migration is not supported then split THP. That behavior was
> > > not very friendly to some usecases, for example, memory policy and
> > > migration lieu of reclaim (the upcoming). But I don't mean we restore
> > > the old behavior. We could split THP if it returns -ENOSYS and the
> > > page is THP.
> >
> > OK, as long as we don't get any broken PMD migration entries established
> > for s390, some extra THP splitting would be acceptable I guess.
> 
> There will be no migration PMD installed. The current behavior is a
> no-op if THP migration is not supported.

Ok, just for completeness, since Mel also replied that the split
was not done on other architectures "because the loss from splitting
exceeded the gain of improved locality":

I did not mean to request extra splitting functionality for s390,
simply skipping / ignoring large PMDs would also be fine for s390,
no need to add extra complexity.

  reply	other threads:[~2021-04-06 12:03 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-29 18:33 [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA hinting fault Yang Shi
2021-03-29 18:33 ` [PATCH 1/6] mm: memory: add orig_pmd to struct vm_fault Yang Shi
2021-03-29 18:33 ` [PATCH 2/6] mm: memory: make numa_migrate_prep() non-static Yang Shi
2021-03-29 18:33 ` [PATCH 3/6] mm: migrate: teach migrate_misplaced_page() about THP Yang Shi
2021-03-30  0:21   ` Huang, Ying
2021-03-30  0:21     ` Huang, Ying
2021-03-30 16:57     ` Yang Shi
2021-03-30 16:57       ` Yang Shi
2021-03-29 18:33 ` [PATCH 4/6] mm: thp: refactor NUMA fault handling Yang Shi
2021-03-30  0:41   ` Huang, Ying
2021-03-30  0:41     ` Huang, Ying
2021-03-30 17:02     ` Yang Shi
2021-03-30 17:02       ` Yang Shi
2021-04-01  2:34   ` kernel test robot
2021-03-29 18:33 ` [PATCH 5/6] mm: migrate: don't split THP for misplaced NUMA page Yang Shi
2021-03-30 14:42   ` Gerald Schaefer
2021-03-30 16:53     ` Yang Shi
2021-03-30 16:53       ` Yang Shi
2021-03-29 18:33 ` [PATCH 6/6] mm: migrate: remove redundant page count check for THP Yang Shi
2021-03-30 14:42 ` [RFC PATCH 0/6] mm: thp: use generic THP migration for NUMA hinting fault Gerald Schaefer
2021-03-30 16:51   ` Yang Shi
2021-03-30 16:51     ` Yang Shi
2021-03-31 11:47     ` Gerald Schaefer
2021-04-01 20:10       ` Yang Shi
2021-04-01 20:10         ` Yang Shi
2021-04-06 12:02         ` Gerald Schaefer [this message]
2021-04-06 16:42           ` Yang Shi
2021-04-06 16:42             ` Yang Shi
2021-04-07  8:32             ` Mel Gorman
2021-04-07 16:04               ` Yang Shi
2021-04-07 16:04                 ` Yang Shi
2021-03-31 13:20   ` Mel Gorman
2021-04-01 20:12     ` Yang Shi
2021-04-01 20:12       ` Yang Shi

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