From: Andrea Arcangeli <aarcange@redhat.com>
To: Nai Xia <nai.xia@gmail.com>
Cc: Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
Pawel Sikora <pluto@agmk.net>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, jpiszcz@lucidpixels.com, arekm@pld-linux.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mremap: skip page table lookup for non-faulted anonymous VMAs
Date: Mon, 7 Nov 2011 16:32:20 +0100 [thread overview]
Message-ID: <20111107153220.GD3249@redhat.com> (raw)
In-Reply-To: <201111071221.35403.nai.xia@gmail.com>
On Mon, Nov 07, 2011 at 12:21:35PM +0800, Nai Xia wrote:
> If an anonymous vma has not yet been faulted, move_page_tables() in move_vma()
> is not necessary for it.
I actually thought of adding that (in fact fork has it and it's more
likely to be beneficial for fork than for mremap I suspect), but this
adds a branch to the fast path for a case that shouldn't normally
materialize. So I don't think it's worth adding it as I expect it to
add overhead in average.
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com>
To: Nai Xia <nai.xia@gmail.com>
Cc: Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
Pawel Sikora <pluto@agmk.net>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, jpiszcz@lucidpixels.com, arekm@pld-linux.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mremap: skip page table lookup for non-faulted anonymous VMAs
Date: Mon, 7 Nov 2011 16:32:20 +0100 [thread overview]
Message-ID: <20111107153220.GD3249@redhat.com> (raw)
In-Reply-To: <201111071221.35403.nai.xia@gmail.com>
On Mon, Nov 07, 2011 at 12:21:35PM +0800, Nai Xia wrote:
> If an anonymous vma has not yet been faulted, move_page_tables() in move_vma()
> is not necessary for it.
I actually thought of adding that (in fact fork has it and it's more
likely to be beneficial for fork than for mremap I suspect), but this
adds a branch to the fast path for a case that shouldn't normally
materialize. So I don't think it's worth adding it as I expect it to
add overhead in average.
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next prev parent reply other threads:[~2011-11-07 15:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-07 4:21 [PATCH] mremap: skip page table lookup for non-faulted anonymous VMAs Nai Xia
2011-11-07 4:21 ` Nai Xia
2011-11-07 15:32 ` Andrea Arcangeli [this message]
2011-11-07 15:32 ` Andrea Arcangeli
2011-11-07 16:13 ` Nai Xia
2011-11-07 16:13 ` Nai Xia
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