From: Christopher Lameter <cl@linux.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Henry Willard <henry.willard@oracle.com>,
akpm@linux-foundation.org, kstewart@linuxfoundation.org,
zi.yan@cs.rutgers.edu, pombredanne@nexb.com, aarcange@redhat.com,
gregkh@linuxfoundation.org, aneesh.kumar@linux.vnet.ibm.com,
kirill.shutemov@linux.intel.com, jglisse@redhat.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: numa: Do not trap faults on shared data section pages.
Date: Wed, 17 Jan 2018 12:23:04 -0600 (CST) [thread overview]
Message-ID: <alpine.DEB.2.20.1801171219270.23209@nuc-kabylake> (raw)
In-Reply-To: <20180116212614.gudglzw7kwzd3get@suse.de>
On Tue, 16 Jan 2018, Mel Gorman wrote:
> My main source of discomfort is the fact that this is permanent as two
> processes perfectly isolated but with a suitably shared COW mapping
> will never migrate the data. A potential improvement to get the reported
> bandwidth up in the test program would be to skip the rest of the VMA if
> page_mapcount != 1 in a COW mapping as it would be reasonable to assume
> the remaining pages in the VMA are also affected and the scan is wasteful.
> There are counter-examples to this but I suspect that the full VMA being
> shared is the common case. Whether you do that or not;
Same concern here. Typically CAP_SYS_NICE will bypass the check that the
page is only mapped to a single process and the check looks exactly like
the ones for manual migration. Using CAP_SYS_NICE would be surprising
here since autonuma is not triggered by the currently running process.
Can we configure this somehow via sysfs?
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next prev parent reply other threads:[~2018-01-17 18:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-16 19:28 [PATCH] mm: numa: numa balancing performance problem Henry Willard
2018-01-16 19:28 ` [PATCH] mm: numa: Do not trap faults on shared data section pages Henry Willard
2018-01-16 21:26 ` Mel Gorman
2018-01-17 0:45 ` Henry Willard
2018-01-17 18:23 ` Christopher Lameter [this message]
2018-01-19 1:06 ` Henry Willard
2018-01-20 2:12 ` Christopher Lameter
2018-01-23 0:41 ` Henry Willard
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