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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Christoph Lameter <clameter@sgi.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Andrew Morton <akpm@osdl.org>,
	Nick Piggin <nickpiggin@yahoo.com.au>,
	Ingo Molnar <mingo@elte.hu>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 00/14] Concurrent Page Cache
Date: Mon, 29 Jan 2007 19:56:17 +0100	[thread overview]
Message-ID: <1170096978.10987.39.camel@lappy> (raw)
In-Reply-To: <Pine.LNX.4.64.0701291013530.29254@schroedinger.engr.sgi.com>

On Mon, 2007-01-29 at 10:15 -0800, Christoph Lameter wrote:
> On Mon, 29 Jan 2007, Peter Zijlstra wrote:
> 
> > Ladder locking would end up:
> > 
> > lock A0
> > lock B1
> > unlock A0 -> a new operation can start
> > lock C2
> > unlock B1
> > lock D5
> > unlock C2
> > ** we do stuff to D5
> > unlock D5
> > 
> 
> Instead of taking one lock we would need to take 4?

Yep.

> Wont doing so cause significant locking overhead?
> We probably would want to run some benchmarks. 

Right, I was hoping the extra locking overhead would be more than
compensated by the reduction in lock contention time. But testing is
indeed in order.

> Maybe disable the scheme for systems with a small number of 
> processors?

CONFIG_RADIX_TREE_CONCURRENT does exactly this.


      reply	other threads:[~2007-01-29 18:56 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-28 13:13 Peter Zijlstra
2007-01-28 13:13 ` [PATCH 01/14] radix-tree: use indirect bit Peter Zijlstra
2007-01-28 13:13 ` [PATCH 02/14] radix-tree: gang_lookup_slot Peter Zijlstra
2007-01-28 13:13 ` [PATCH 03/14] radix-tree: gang_lookup_tag_slot Peter Zijlstra
2007-01-28 13:13 ` [PATCH 04/14] mm: speculative get page Peter Zijlstra
2007-01-28 13:13 ` [PATCH 05/14] mm: lockless pagecache lookups Peter Zijlstra
2007-01-28 13:13 ` [PATCH 06/14] mm: fix speculative page get preemption bug Peter Zijlstra
2007-01-28 13:13 ` [PATCH 07/14] mm: speculative find_get_pages_tag Peter Zijlstra
2007-01-28 13:13 ` [PATCH 08/14] mm: remove find_tylock_page Peter Zijlstra
2007-01-28 13:13 ` [PATCH 09/14] mm: change tree_lock into a spinlock Peter Zijlstra
2007-01-28 13:13 ` [PATCH 10/14] radix-tree: concurrent write side support Peter Zijlstra
2007-01-28 13:13 ` [PATCH 11/14] atomic_ulong_t Peter Zijlstra
2007-01-29 17:11   ` Christoph Lameter
2007-01-28 13:13 ` [PATCH 12/14] mm/fs: abstract address_space::nrpages Peter Zijlstra
2007-01-28 13:13 ` [PATCH 13/14] mm: lock_page_ref Peter Zijlstra
2007-01-28 13:13 ` [PATCH 14/14] mm: concurrent pagecache write side Peter Zijlstra
2007-01-29 17:20 ` [PATCH 00/14] Concurrent Page Cache Christoph Lameter
2007-01-29 18:05   ` Peter Zijlstra
2007-01-29 18:15     ` Christoph Lameter
2007-01-29 18:56       ` Peter Zijlstra [this message]

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