From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Christoph Lameter <clameter@engr.sgi.com>
Cc: Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>,
Hugh Dickins <hugh@veritas.com>,
Nick Piggin <piggin@cyberone.com.au>,
linux-mm@kvack.org
Subject: Re: pagefault scalability patches
Date: Mon, 22 Aug 2005 12:13:43 +1000 [thread overview]
Message-ID: <1124676823.5159.12.camel@gaston> (raw)
In-Reply-To: <Pine.LNX.4.62.0508171550001.19273@schroedinger.engr.sgi.com>
On Wed, 2005-08-17 at 15:51 -0700, Christoph Lameter wrote:
> On Wed, 17 Aug 2005, Linus Torvalds wrote:
>
> > HOWEVER, the fact that it makes the mm counters be atomic just makes it
> > pointless. It may help scalability, but it loses the attribute that I
> > considered a big win above - it no longer helps the non-contended case (at
> > least on x86, a uncontended spinlock is about as expensive as a atomic
> > op).
>
> We are trading 2x (spinlock(page_table_lock),
> spin_unlock(page_table_lock)) against one atomic inc.
At least on ppc, unlock isn't atomic
> > I thought Christoph (Nick?) had a patch to make the counters be
> > per-thread, and then just folded back into the mm-struct every once in a
> > while?
>
> Yes I do but I did want want to risk that can of worms becoming entwined
> with the page fault scalability patches.
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next prev parent reply other threads:[~2005-08-22 2:13 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-17 22:17 pagefault scalability patches Andrew Morton
2005-08-17 22:19 ` Christoph Lameter
2005-08-17 22:36 ` Linus Torvalds
2005-08-17 22:51 ` Christoph Lameter
2005-08-17 23:01 ` Linus Torvalds
2005-08-17 23:12 ` Christoph Lameter
2005-08-17 23:23 ` Linus Torvalds
2005-08-17 23:31 ` Christoph Lameter
2005-08-17 23:30 ` Andrew Morton
2005-08-17 23:33 ` Christoph Lameter
2005-08-17 23:44 ` Andrew Morton
2005-08-17 23:52 ` Peter Chubb
2005-08-17 23:58 ` Christoph Lameter
2005-08-18 0:47 ` Andrew Morton
2005-08-18 16:09 ` Christoph Lameter
2005-08-22 2:13 ` Benjamin Herrenschmidt [this message]
2005-08-18 0:43 ` Andrew Morton
2005-08-18 16:04 ` Christoph Lameter
2005-08-18 20:16 ` Hugh Dickins
2005-08-19 1:22 ` [PATCH] use mm_counter macros for nr_pte since its also under ptl Christoph Lameter
2005-08-19 3:17 ` Andrew Morton
2005-08-19 3:51 ` Christoph Lameter
2005-08-19 1:33 ` pagefault scalability patches Christoph Lameter
2005-08-19 3:53 ` [RFC] Concept for delayed counter updates in mm_struct Christoph Lameter
2005-08-19 4:29 ` Andrew Morton
2005-08-19 4:34 ` Andi Kleen
2005-08-19 4:49 ` Linus Torvalds
2005-08-19 16:06 ` Christoph Lameter
2005-08-20 7:33 ` [PATCH] mm_struct counter deltas in task_struct Christoph Lameter
2005-08-20 7:35 ` [PATCH] Use deltas to replace atomic inc Christoph Lameter
2005-08-20 7:58 ` Andrew Morton
2005-08-22 3:32 ` Christoph Lameter
2005-08-22 3:48 ` Linus Torvalds
2005-08-22 4:06 ` Christoph Lameter
2005-08-22 4:18 ` Linus Torvalds
2005-08-22 13:23 ` Christoph Lameter
2005-08-22 14:22 ` Hugh Dickins
2005-08-22 15:24 ` Christoph Lameter
2005-08-22 15:43 ` Andi Kleen
2005-08-22 16:24 ` Christoph Lameter
2005-08-22 20:30 ` [PATCH] mm_struct counter deltas V2 Christoph Lameter
2005-08-22 20:31 ` [PATCH] Use deltas to replace atomic inc V2 Christoph Lameter
2005-08-22 2:09 ` pagefault scalability patches Benjamin Herrenschmidt
2005-08-18 2:00 ` Nick Piggin
2005-08-18 8:38 ` Nick Piggin
2005-08-18 16:17 ` Christoph Lameter
2005-08-22 2:04 ` Benjamin Herrenschmidt
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