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From: Christoph Hellwig <hch@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	fengguang.wu@intel.com, mel@csn.ul.ie, npiggin@suse.de,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: what is the point of nr_pages information for the flusher thread?
Date: Wed, 7 Jul 2010 19:43:16 -0400	[thread overview]
Message-ID: <20100707234316.GA21990@infradead.org> (raw)
In-Reply-To: <20100707163710.a46173b2.akpm@linux-foundation.org>

On Wed, Jul 07, 2010 at 04:37:10PM -0700, Andrew Morton wrote:
> On Wed, 7 Jul 2010 19:16:11 -0400
> Christoph Hellwig <hch@infradead.org> wrote:
> 
> > Currently there's three possible values we pass into the flusher thread
> > for the nr_pages arguments:
> 
> I assume you're referring to wakeup_flusher_threads().

In that context I refer to everything using the per-bdi flusher thread.
That includes wakeup_flusher_threads() and the functions I've mentioned
below.

> There's also free_more_memory() and do_try_to_free_pages().

Indeed.  So we still have some special cases that want a specific
number to be written back globally.

> wakeup_flusher_threads() apepars to have been borked.  It passes
> nr_pages() into *each* bdi hence can write back far more than it was
> asked to.

> > But seriously, how is the _global_ number of dirty and unstable pages
> > a good indicator for the amount of writeback per-bdi or superblock
> > anyway?
> 
> It isn't.  This appears to have been an attempt to transport the
> wakeup_pdflush() functionality into the new wakeup_flusher_threads()
> regime.  Badly.

Unfortunately we don't just use it for wakeup_flusher_threads() but
also for various bits of per-bdi and per-sb writeback.


WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	fengguang.wu@intel.com, mel@csn.ul.ie, npiggin@suse.de,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: what is the point of nr_pages information for the flusher thread?
Date: Wed, 7 Jul 2010 19:43:16 -0400	[thread overview]
Message-ID: <20100707234316.GA21990@infradead.org> (raw)
In-Reply-To: <20100707163710.a46173b2.akpm@linux-foundation.org>

On Wed, Jul 07, 2010 at 04:37:10PM -0700, Andrew Morton wrote:
> On Wed, 7 Jul 2010 19:16:11 -0400
> Christoph Hellwig <hch@infradead.org> wrote:
> 
> > Currently there's three possible values we pass into the flusher thread
> > for the nr_pages arguments:
> 
> I assume you're referring to wakeup_flusher_threads().

In that context I refer to everything using the per-bdi flusher thread.
That includes wakeup_flusher_threads() and the functions I've mentioned
below.

> There's also free_more_memory() and do_try_to_free_pages().

Indeed.  So we still have some special cases that want a specific
number to be written back globally.

> wakeup_flusher_threads() apepars to have been borked.  It passes
> nr_pages() into *each* bdi hence can write back far more than it was
> asked to.

> > But seriously, how is the _global_ number of dirty and unstable pages
> > a good indicator for the amount of writeback per-bdi or superblock
> > anyway?
> 
> It isn't.  This appears to have been an attempt to transport the
> wakeup_pdflush() functionality into the new wakeup_flusher_threads()
> regime.  Badly.

Unfortunately we don't just use it for wakeup_flusher_threads() but
also for various bits of per-bdi and per-sb writeback.

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  reply	other threads:[~2010-07-07 23:43 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-07-07 23:16 what is the point of nr_pages information for the flusher thread? Christoph Hellwig
2010-07-07 23:16 ` Christoph Hellwig
2010-07-07 23:37 ` Andrew Morton
2010-07-07 23:37   ` Andrew Morton
2010-07-07 23:43   ` Christoph Hellwig [this message]
2010-07-07 23:43     ` Christoph Hellwig
2010-07-07 23:55     ` Andrew Morton
2010-07-10 14:58 ` Wu Fengguang

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