linux-kernel - Re: [PATCH v2] fs/ext4: increase parallelism in updating ext4 orphan list

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Message-ID: <20140415172522.GA13276@quack.suse.cz>
Date:	Tue, 15 Apr 2014 19:25:22 +0200
From:	Jan Kara <jack@...e.cz>
To:	Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@...com>
Cc:	Jan Kara <jack@...e.cz>, T Makphaibulchoke <tmac@...com>,
	tytso@....edu, adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	aswin@...com
Subject: Re: [PATCH v2] fs/ext4: increase parallelism in updating ext4 orphan
 list

On Tue 15-04-14 10:27:46, Thavatchai Makphaibulchoke wrote:
> On 04/14/2014 11:40 AM, Jan Kara wrote:
> >   Thanks for trying that out! Can you please send me a patch you have been
> > testing? Because it doesn't quite make sense to me why using i_mutex should
> > be worse than using hashed locks...
> >
> 
> Thanks again for the comments.
> 
> Since i_mutex is also used for serialization in other operations on an
> inode, in the case that the i_mutex is not held  using it for
> serialization could cause contention with other operations on the inode.
> As the number shows substantial instances of orphan add or delete calls
> without holding the i_mutex, I presume the performance degradation is due
> to the contention.
  I have checked the source and I didn't find many places where i_mutex was
not held. But maybe I'm wrong. That's why I wanted to see the patch where
you are using i_mutex instead of hashed mutexes and which didn't perform
good enough.

> As for the patch, could you please let me know if you need the patch
> using i_mutex or the patch I'm planning to submit.  If it's the latter,
> I'm thinking of go ahead and resubmit it.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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