From: Andi Kleen <andi@firstfloor.org>
To: Shaohua Li <shaohua.li@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
lkml <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH]mmap: not merge cloned VMA
Date: Mon, 28 Mar 2011 09:57:06 -0700 [thread overview]
Message-ID: <m2k4fj18v1.fsf@firstfloor.org> (raw)
In-Reply-To: <1301277534.3981.26.camel@sli10-conroe> (Shaohua Li's message of "Mon, 28 Mar 2011 09:58:54 +0800")
Shaohua Li <shaohua.li@intel.com> writes:
> Avoid merging a VMA with another VMA which is cloned from parent process. The
> cloned VMA shares lock with parent process's VMA. If we do the merge, more vma
> area (even the new range is only for current process) uses perent process's
> anon_vma lock, so introduces scalability issues.
> find_mergeable_anon_vma already considers this.
In theory this could prevent quite some VMA merging, but I guess the
tradeoff is worth it and that should be unlikely to hit anyways.
> static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
> - struct anon_vma *anon_vma2)
> + struct anon_vma *anon_vma2,
> + struct vm_area_struct *vma)
> {
> - return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
> + if ((!anon_vma1 || !anon_vma2) && (!vma ||
> + list_is_singular(&vma->anon_vma_chain)))
> + return 1;
I think this if () needs a comment.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Shaohua Li <shaohua.li@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
lkml <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH]mmap: not merge cloned VMA
Date: Mon, 28 Mar 2011 09:57:06 -0700 [thread overview]
Message-ID: <m2k4fj18v1.fsf@firstfloor.org> (raw)
In-Reply-To: <1301277534.3981.26.camel@sli10-conroe> (Shaohua Li's message of "Mon, 28 Mar 2011 09:58:54 +0800")
Shaohua Li <shaohua.li@intel.com> writes:
> Avoid merging a VMA with another VMA which is cloned from parent process. The
> cloned VMA shares lock with parent process's VMA. If we do the merge, more vma
> area (even the new range is only for current process) uses perent process's
> anon_vma lock, so introduces scalability issues.
> find_mergeable_anon_vma already considers this.
In theory this could prevent quite some VMA merging, but I guess the
tradeoff is worth it and that should be unlikely to hit anyways.
> static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
> - struct anon_vma *anon_vma2)
> + struct anon_vma *anon_vma2,
> + struct vm_area_struct *vma)
> {
> - return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2);
> + if ((!anon_vma1 || !anon_vma2) && (!vma ||
> + list_is_singular(&vma->anon_vma_chain)))
> + return 1;
I think this if () needs a comment.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
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next prev parent reply other threads:[~2011-03-28 16:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-28 1:58 [PATCH]mmap: not merge cloned VMA Shaohua Li
2011-03-28 1:58 ` Shaohua Li
2011-03-28 16:57 ` Andi Kleen [this message]
2011-03-28 16:57 ` Andi Kleen
2011-03-29 0:53 ` Shaohua Li
2011-03-29 0:53 ` Shaohua Li
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