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Message-ID: <20130130052658.GE25006@thunk.org> Date: Wed, 30 Jan 2013 00:26:58 -0500 From: Theodore Ts'o <tytso@....edu> To: Jan Kara <jack@...e.cz> Cc: Eric Sandeen <sandeen@...hat.com>, Sedat Dilek <sedat.dilek@...il.com>, Ext4 Developers List <linux-ext4@...r.kernel.org>, mszeredi@...e.cz Subject: Re: jbd2: don't wake kjournald unnecessarily 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? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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