linux-ext4 - Re: [PATCH 1/2] jbd2: Avoid pointless scanning of checkpoint lists

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Message-ID: <20140918044744.GE24887@thunk.org>
Date:	Thu, 18 Sep 2014 00:47:44 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org,
	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
Subject: Re: [PATCH 1/2] jbd2: Avoid pointless scanning of checkpoint lists

On Wed, Sep 17, 2014 at 11:31:29AM +0200, Jan Kara wrote:
> Yuanhan has reported that when he is running fsync(2) heavy workload
> creating new files over ramdisk, significant amount of time is spent in
> __jbd2_journal_clean_checkpoint_list() trying to clean old transactions
> (but they cannot be cleaned up because flusher hasn't yet checkpointed
> those buffers). The workload can be generated by:
>   fs_mark -d /fs/ram0/1 -D 2 -N 2560 -n 1000000 -L 1 -S 1 -s 4096
> 
> Reduce the amount of scanning by stopping to scan the transaction list
> once we find a transaction that cannot be checkpointed. Note that this
> way of cleaning is still enough to keep freeing space in the journal
> after fully checkpointed transactions.
> 
> Reported-and-tested-by: Yuanhan Liu <yuanhan.liu@...ux.intel.com>
> Signed-off-by: Jan Kara <jack@...e.cz>

Applied, thanks.

					- Ted
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