From: Andrew Morton <akpm@osdl.org>
To: Paul Mackerras <paulus@samba.org>
Cc: clameter@sgi.com, linux-ia64@vger.kernel.org, torvalds@osdl.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: Prezeroing V2 [0/3]: Why and When it works
Date: Thu, 23 Dec 2004 13:37:45 -0800 [thread overview]
Message-ID: <20041223133745.1d95bb08.akpm@osdl.org> (raw)
In-Reply-To: <16843.13418.630413.64809@cargo.ozlabs.ibm.com>
Paul Mackerras <paulus@samba.org> wrote:
>
> Christoph Lameter writes:
>
> > The most expensive operation in the page fault handler is (apart of SMP
> > locking overhead) the zeroing of the page.
>
> Re-reading this I see that you mean the zeroing of the page that is
> mapped into the process address space, not the page table pages. So
> ignore my previous reply.
>
> Do you have any statistics on how often a page fault needs to supply a
> page of zeroes versus supplying a copy of an existing page, for real
> applications?
When the workload is a gcc run, the pagefault handler dominates the system
time. That's the page zeroing.
> In any case, unless you have magic page-zeroing hardware, I am still
> inclined to think that zeroing the page at the time of the fault is
> the most efficient, since that means the page will be hot in the cache
> for the process to use. If you zero it earlier using CPU stores, it
> can only cause more overall memory traffic, as far as I can see.
x86's movnta instructions provide a way of initialising memory without
trashing the caches and it has pretty good bandwidth, I believe. We should
wire that up to these patches and see if it speeds things up.
> I did some measurements once on my G5 powermac (running a ppc64 linux
> kernel) of how long clear_page takes, and it only takes 96ns for a 4kB
> page.
40GB/s. Is that straight into L1 or does the measurement include writeback?
next prev parent reply other threads:[~2004-12-23 21:33 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <B8E391BBE9FE384DAA4C5C003888BE6F02900FBD@scsmsx401.amr.corp.intel.com>
[not found] ` <41C20E3E.3070209@yahoo.com.au>
2004-12-21 19:55 ` Increase page fault rate by prezeroing V1 [0/3]: Overview Christoph Lameter
2004-12-21 19:56 ` Increase page fault rate by prezeroing V1 [1/3]: Introduce __GFP_ZERO Christoph Lameter
2004-12-21 19:57 ` Increase page fault rate by prezeroing V1 [2/3]: zeroing and scrubd Christoph Lameter
2005-01-01 2:22 ` Nick Piggin
2005-01-01 2:55 ` pmarques
2004-12-21 19:57 ` Increase page fault rate by prezeroing V1 [3/3]: Altix SN2 BTE Zeroing Christoph Lameter
2004-12-22 12:46 ` Robin Holt
2004-12-22 19:56 ` Christoph Lameter
2004-12-23 19:29 ` Prezeroing V2 [0/3]: Why and When it works Christoph Lameter
2004-12-23 19:33 ` Prezeroing V2 [1/4]: __GFP_ZERO / clear_page() removal Christoph Lameter
2004-12-23 19:33 ` Prezeroing V2 [2/4]: add second parameter to clear_page() for all arches Christoph Lameter
2004-12-24 8:33 ` Pavel Machek
2004-12-24 16:18 ` Christoph Lameter
2004-12-24 16:27 ` Pavel Machek
2004-12-24 17:02 ` David S. Miller
2004-12-24 17:05 ` David S. Miller
2004-12-27 22:48 ` David S. Miller
2005-01-03 17:52 ` Christoph Lameter
2005-01-01 10:24 ` Geert Uytterhoeven
2005-01-04 23:12 ` Prezeroing V3 [0/4]: Discussion and i386 performance tests Christoph Lameter
2005-01-04 23:13 ` Prezeroing V3 [1/4]: Allow request for zeroed memory Christoph Lameter
2005-01-04 23:45 ` Dave Hansen
2005-01-05 1:16 ` Christoph Lameter
2005-01-05 1:26 ` Linus Torvalds
2005-01-05 23:11 ` Christoph Lameter
2005-01-05 0:34 ` Linus Torvalds
2005-01-05 0:47 ` Andrew Morton
2005-01-05 1:15 ` Christoph Lameter
2005-01-08 21:12 ` Hugh Dickins
2005-01-08 21:56 ` David S. Miller
2005-01-21 20:09 ` alloc_zeroed_user_highpage to fix the clear_user_highpage issue Christoph Lameter
2005-02-09 9:58 ` [Patch] Fix oops in alloc_zeroed_user_highpage() when page is NULL Michael Ellerman
2005-02-10 0:38 ` Christoph Lameter
2005-01-21 20:12 ` Extend clear_page by an order parameter Christoph Lameter
2005-01-21 22:29 ` Paul Mackerras
2005-01-21 23:48 ` Christoph Lameter
2005-01-22 0:35 ` Paul Mackerras
2005-01-22 0:43 ` Andrew Morton
2005-01-22 1:08 ` Paul Mackerras
2005-01-22 1:20 ` Roman Zippel
2005-01-22 1:25 ` Paul Mackerras
2005-01-22 1:54 ` Christoph Lameter
2005-01-22 2:53 ` Paul Mackerras
2005-01-23 7:45 ` Andrew Morton
2005-01-24 16:37 ` Christoph Lameter
2005-01-24 20:23 ` David S. Miller
2005-01-24 20:33 ` Christoph Lameter
2005-01-21 20:15 ` A scrub daemon (prezeroing) Christoph Lameter
2005-01-10 17:16 ` Prezeroing V3 [1/4]: Allow request for zeroed memory Christoph Lameter
2005-01-10 18:13 ` Linus Torvalds
2005-01-10 20:17 ` Christoph Lameter
2005-01-10 23:53 ` Prezeroing V4 [0/4]: Overview Christoph Lameter
2005-01-10 23:54 ` Prezeroing V4 [1/4]: Arch specific page zeroing during page fault Christoph Lameter
2005-01-11 0:41 ` Chris Wright
2005-01-11 0:46 ` Christoph Lameter
2005-01-11 0:49 ` Chris Wright
2005-01-10 23:55 ` Prezeroing V4 [2/4]: Zeroing implementation Christoph Lameter
2005-01-10 23:55 ` Prezeroing V4 [3/4]: Altix SN2 BTE zero driver Christoph Lameter
2005-01-10 23:56 ` Prezeroing V4 [4/4]: Extend clear_page to take an order parameter Christoph Lameter
2005-01-04 23:14 ` Prezeroing V3 [2/4]: Extension of " Christoph Lameter
2005-01-05 23:25 ` Christoph Lameter
2005-01-06 13:52 ` Andi Kleen
2005-01-06 17:47 ` Christoph Lameter
2005-01-04 23:15 ` Prezeroing V3 [3/4]: Page zeroing through kscrubd Christoph Lameter
2005-01-04 23:16 ` Prezeroing V3 [4/4]: Driver for hardware zeroing on Altix Christoph Lameter
2005-01-05 2:16 ` Andi Kleen
2005-01-05 16:24 ` Christoph Lameter
2004-12-23 19:34 ` Prezeroing V2 [3/4]: Add support for ZEROED and NOT_ZEROED free maps Christoph Lameter
2004-12-23 19:35 ` Prezeroing V2 [4/4]: Hardware Zeroing through SGI BTE Christoph Lameter
2004-12-23 20:08 ` Prezeroing V2 [1/4]: __GFP_ZERO / clear_page() removal Brian Gerst
2004-12-24 16:24 ` Christoph Lameter
2004-12-23 19:49 ` Prezeroing V2 [0/3]: Why and When it works Arjan van de Ven
2004-12-23 20:57 ` Matt Mackall
2004-12-23 21:01 ` Paul Mackerras
2004-12-23 21:11 ` Paul Mackerras
2004-12-23 21:37 ` Andrew Morton [this message]
2004-12-23 23:00 ` Paul Mackerras
2004-12-23 21:48 ` Linus Torvalds
2004-12-23 22:34 ` Zwane Mwaikambo
2004-12-24 9:14 ` Arjan van de Ven
2004-12-24 18:21 ` Linus Torvalds
2004-12-24 18:57 ` Arjan van de Ven
2004-12-27 22:50 ` David S. Miller
2004-12-28 11:53 ` Marcelo Tosatti
2004-12-24 16:17 ` Christoph Lameter
2004-12-24 18:31 ` Increase page fault rate by prezeroing V1 [0/3]: Overview Andrea Arcangeli
2005-01-03 17:54 ` Christoph Lameter
[not found] <B8E391BBE9FE384DAA4C5C003888BE6F02900FBD@scsmsx401.amr.corp.intel.com.suse.lists.linux.kernel>
[not found] ` <41C20E3E.3070209@yahoo.com.au.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0412211154100.1313@schroedinger.engr.sgi.com.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.58.0412231119540.31791@schroedinger.engr.sgi.com.suse.lists.linux.kernel>
2004-12-23 20:27 ` Prezeroing V2 [0/3]: Why and When it works Andi Kleen
2004-12-23 21:02 ` Christoph Lameter
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