From: Andrew Morton <akpm@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, Andi Kleen <ak@linux.intel.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [PATCH v5 09/11] thp: lazy huge zero page allocation
Date: Wed, 12 Dec 2012 13:30:51 -0800 [thread overview]
Message-ID: <20121212133051.6dad3722.akpm@linux-foundation.org> (raw)
In-Reply-To: <20121115094155.GG9676@otc-wbsnb-06>
On Thu, 15 Nov 2012 11:41:55 +0200
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
> On Wed, Nov 14, 2012 at 03:37:09PM -0800, David Rientjes wrote:
> > On Wed, 7 Nov 2012, Kirill A. Shutemov wrote:
> >
> > > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> > >
> > > Instead of allocating huge zero page on hugepage_init() we can postpone it
> > > until first huge zero page map. It saves memory if THP is not in use.
> > >
> >
> > Is it worth the branch on every non-write pagefault after that? The
> > unlikely() is not going to help on x86. If thp is enabled in your
> > .config (which isn't the default), then I think it's better to just
> > allocate the zero huge page once and avoid any branches after that to
> > lazily allocate it. (Or do it only when thp is set to "madvise" or
> > "always" if booting with transparent_hugepage=never.)
>
> I can rewrite the check to static_key if you want. Would it be better?
The new test-n-branch only happens on the first read fault against a
thp huge page, yes? In which case it's a quite infrequent event and I
suspect this isn't worth bothering about.
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next prev parent reply other threads:[~2012-12-12 21:30 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-07 15:00 [PATCH v5 00/11] Introduce huge zero page Kirill A. Shutemov
2012-11-07 15:00 ` [PATCH v5 01/11] thp: huge zero page: basic preparation Kirill A. Shutemov
2012-11-14 22:09 ` David Rientjes
2012-11-07 15:00 ` [PATCH v5 02/11] thp: zap_huge_pmd(): zap huge zero pmd Kirill A. Shutemov
2012-11-14 22:18 ` David Rientjes
2012-11-07 15:00 ` [PATCH v5 03/11] thp: copy_huge_pmd(): copy huge zero page Kirill A. Shutemov
2012-11-14 22:33 ` David Rientjes
2012-11-15 8:01 ` Kirill A. Shutemov
2012-11-15 8:14 ` David Rientjes
2012-11-07 15:00 ` [PATCH v5 04/11] thp: do_huge_pmd_wp_page(): handle " Kirill A. Shutemov
2012-11-14 23:08 ` David Rientjes
2012-11-15 8:29 ` Kirill A. Shutemov
2012-11-07 15:00 ` [PATCH v5 05/11] thp: change_huge_pmd(): keep huge zero page write-protected Kirill A. Shutemov
2012-11-14 23:12 ` David Rientjes
2012-11-15 8:46 ` Kirill A. Shutemov
2012-11-15 21:47 ` David Rientjes
2012-11-16 18:13 ` Kirill A. Shutemov
2012-11-16 20:10 ` David Rientjes
2012-11-20 16:00 ` Kirill A. Shutemov
2012-12-03 9:53 ` Kirill A. Shutemov
2012-11-07 15:00 ` [PATCH v5 06/11] thp: change split_huge_page_pmd() interface Kirill A. Shutemov
2012-11-14 23:22 ` David Rientjes
2012-11-15 8:52 ` Kirill A. Shutemov
2012-11-07 15:00 ` [PATCH v5 07/11] thp: implement splitting pmd for huge zero page Kirill A. Shutemov
2012-11-14 23:28 ` David Rientjes
2012-11-15 9:24 ` Kirill A. Shutemov
2012-11-07 15:01 ` [PATCH v5 08/11] thp: setup huge zero page on non-write page fault Kirill A. Shutemov
2012-11-14 23:33 ` David Rientjes
2012-11-15 9:32 ` Kirill A. Shutemov
2012-11-15 21:52 ` David Rientjes
2012-11-16 18:20 ` Kirill A. Shutemov
2012-11-07 15:01 ` [PATCH v5 09/11] thp: lazy huge zero page allocation Kirill A. Shutemov
2012-11-14 23:37 ` David Rientjes
2012-11-15 9:41 ` Kirill A. Shutemov
2012-12-12 21:30 ` Andrew Morton [this message]
2012-12-12 21:48 ` H. Peter Anvin
2012-12-12 22:05 ` Kirill A. Shutemov
2012-11-07 15:01 ` [PATCH v5 10/11] thp: implement refcounting for huge zero page Kirill A. Shutemov
2012-11-14 23:40 ` David Rientjes
2012-11-15 9:50 ` Kirill A. Shutemov
2012-11-07 15:01 ` [PATCH v5 11/11] thp, vmstat: implement HZP_ALLOC and HZP_ALLOC_FAILED events Kirill A. Shutemov
2012-11-14 23:41 ` David Rientjes
2012-11-16 21:29 ` H. Peter Anvin
2012-11-14 21:33 ` [PATCH v5 00/11] Introduce huge zero page Andrew Morton
2012-11-14 23:20 ` Alan Cox
2012-11-14 23:32 ` Andrew Morton
2012-11-14 23:51 ` H. Peter Anvin
2012-11-15 0:29 ` David Rientjes
2012-11-15 7:29 ` Kirill A. Shutemov
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