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From: Adrian Hunter <adrian.hunter@intel.com>
To: Andreas Dilger <adilger.kernel@dilger.ca>,
	"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
	Theodore Ts'o <tytso@mit.edu>
Subject: jbd2_clear_buffer_revoked_flags() takes a long time
Date: Wed, 10 Oct 2018 16:43:27 +0300	[thread overview]
Message-ID: <d2e1ec1a-0d7d-1acb-6887-c55ac30e4a3a@intel.com> (raw)

Hi

I have a case on a v4.14 kernel where the EXT4 journal commit disables
preemption for 30ms due to jbd2_clear_buffer_revoked_flags().  That in turn
disables preemption on other CPUs as they come to spin waiting for the same
lock.  The side-effect of that is that it periodically blocks high priority
tasks from running.

I see jbd2_clear_buffer_revoked_flags() iterating 32768 times calling
__find_get_block().

Is there any way to make jbd2_clear_buffer_revoked_flags() take less time,
or move its work out from under write_lock(&journal->j_state_lock)?

Or do you have any other suggestions?

Regards
Adrian

             reply	other threads:[~2018-10-10 21:07 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-10 13:43 Adrian Hunter [this message]
2018-10-10 17:49 ` jbd2_clear_buffer_revoked_flags() takes a long time Theodore Y. Ts'o
2018-10-11 11:12   ` Jan Kara
2018-10-11 12:38     ` Adrian Hunter
2018-10-16  8:49       ` Adrian Hunter
2018-10-16  9:50         ` Jan Kara

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