From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Christoph Lameter <clameter@sgi.com>
Cc: akpm@osdl.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-mm@kvack.org, Nikita Danilov <nikita@clusterfs.com>,
Andi Kleen <ak@suse.de>
Subject: Re: [RFC 0/8] Use ZVCs for accurate writeback ratio determination
Date: Fri, 26 Jan 2007 23:22:05 +1100 [thread overview]
Message-ID: <45B9F26D.5090107@yahoo.com.au> (raw)
In-Reply-To: <20070126054153.10564.43218.sendpatchset@schroedinger.engr.sgi.com>
Christoph Lameter wrote:
> The determination of the dirty ratio to determine writeback behavior
> is currently based on the number of total pages on the system.
>
> However, not all pages in the system may be dirtied. Thus the ratio
> is always too low and can never reach 100%. The ratio may be
> particularly skewed if large hugepage allocations, slab allocations
> or device driver buffers make large sections of memory not available
> anymore. In that case we may get into a situation in which f.e. the
> background writeback ratio of 40% cannot be reached anymore which
> leads to undesired writeback behavior.
>
> This patchset fixes that issue by determining the ratio based
> on the actual pages that may potentially be dirty. These are
> the pages on the active and the inactive list plus free pages.
So you no longer account for reclaimable slab allocations, which
would be a significant change on some workloads. Any reason for
that?
--
SUSE Labs, Novell Inc.
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next prev parent reply other threads:[~2007-01-26 12:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-26 5:41 Christoph Lameter
2007-01-26 5:41 ` [RFC 1/8] Use ZVC for inactive and active counts Christoph Lameter
2007-01-26 5:42 ` [RFC 2/8] Use ZVC for free_pages Christoph Lameter
2007-01-26 5:42 ` [RFC 3/8] Reorder ZVCs according to cacheline Christoph Lameter
2007-01-26 5:42 ` [RFC 4/8] Drop free_pages() Christoph Lameter
2007-01-26 5:42 ` [RFC 5/8] Drop nr_free_pages_pgdat() Christoph Lameter
2007-01-26 5:42 ` [RFC 6/8] Drop __get_zone_counts() Christoph Lameter
2007-01-26 5:42 ` [RFC 7/8] Drop get_zone_counts() Christoph Lameter
2007-01-26 5:42 ` [RFC 8/8] Fix writeback calculation Christoph Lameter
2007-01-26 12:22 ` Nick Piggin [this message]
2007-01-26 15:49 ` [RFC 0/8] Use ZVCs for accurate writeback ratio determination Christoph Lameter
2007-01-29 2:40 ` Nick Piggin
2007-01-29 16:56 ` Christoph Lameter
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