linux-ext4 - Re: [PATCH 2/2] percpu_counter: Put a reasonable upper bound on percpu_counter

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Message-ID: <20110829132734.GB12187@thunk.org>
Date:	Mon, 29 Aug 2011 09:27:34 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Anton Blanchard <anton@...ba.org>
Cc:	adilger.kernel@...ger.ca, eric.dumazet@...il.com, tj@...nel.org,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] percpu_counter: Put a reasonable upper bound on
 percpu_counter_batch

On Fri, Aug 26, 2011 at 07:48:52AM -0400, Theodore Tso wrote:
> 
> I understand why we would want to reduce this number.   Unfortunately, the
> question is what do we do if all 1024 threads try to do buffered writes into
> the file system at the same instant, when we have less than 4 megabytes
> of space left?

Oops, sorry, that should be 4 GB of space left (i.e., what do we do if
all 1024 cpu's all try write 1024 4k blocks all at the same time).
Imagine an simulation application where all threads finish at more or
less the same time and then try to write out their data files at the
same time....

							- Ted
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