linux-ext4 - Re: jbd2: don't wake kjournald unnecessarily

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Message-ID: <CA+icZUVR-GG0UYcq=tciCYun+Ayn9YTQAMvcHRu3J1yDDYSsHA@mail.gmail.com>
Date:	Wed, 30 Jan 2013 11:29:02 +0100
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Jan Kara <jack@...e.cz>
Cc:	"Theodore Ts'o" <tytso@....edu>, Eric Sandeen <sandeen@...hat.com>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	mszeredi@...e.cz
Subject: Re: jbd2: don't wake kjournald unnecessarily

On Wed, Jan 30, 2013 at 11:07 AM, Jan Kara <jack@...e.cz> wrote:
> On Wed 30-01-13 00:26:58, Ted Tso wrote:
>> On Wed, Jan 23, 2013 at 08:29:11PM +0100, Jan Kara wrote:
>> > > old JBD: AIM7 jobs/min 97624.39;  got 78193 jbd wakeups
>> > > new JBD: AIM7 jobs/min 85929.43;  got 6306999 jbd wakeups, 6264684 extra wakeups
>> >   Yeah, that's a lot. My guess would be *a lot* of processes are hanging in
>> > start_this_handle() and waiting for transaction commit. Each of them calls
>> > __log_start_commit() and things add up. Thanks for getting these numbers.
>>
>> Yeah, wow.  That would imply that there are a huge number of processes
>> that get hung up in start_this_handle(), and they are waking up the
>> journal before the kjournald has a chance to set T_LOCKED (since then
>> they would get blocked earlier in start_this_handle).
>>
>> Given that, I wonder if the following change would actually help or
>> hurt things.  Eric, would you be willing to ask your perf team to try
>> testing out these patches?
>   Umm, I don't see anything. Forgot to attach them?
>

Here I catched the two patches:

http://patchwork.ozlabs.org/patch/216768/
http://patchwork.ozlabs.org/patch/216767/

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