linux-kernel - Re: [PATCH] async: Don't call async_synchronize_full_special() while holding sb

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Message-ID: <4966D652.4070105@linux.intel.com>
Date:	Thu, 08 Jan 2009 20:45:06 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Grissiom <chaos.proton@...il.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] async: Don't call async_synchronize_full_special()	while
 holding sb_lock

Dave Chinner wrote:

> 
> So, given the potential impact of this change, what testing have
> you done in terms of:
> 
> 	- performance impact

I tested this on my machines and it gave a real performance improvement (11 to 8 seconds for a full kernel tree unlink, and cutting out
latency for normal applications)
> 	- sync() safety
that was exactly the synchronization point that's discussed here.

> 	- removing a million files and queuing all of the
> 	  deletes in the async queues....

the async code throttles at 32k outstanding.
Yes 32K is arbitrary, but if you delete  a million files fast, all but the first few thousand are
synchronous.

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