linux-ext4 - Re: [PATCH] jbd2: Avoid long replay times due to high number or revoke blocks

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Message-ID: <tu5tqgicy4agkzg6uhfw3bawtp472ldmvqa4otgtn2ntetrjo7@q7eb3l5nwlyr>
Date: Fri, 17 Jan 2025 12:11:27 +0100
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...wei.com>
Cc: Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org, 
	Andreas Dilger <adilger@...ger.ca>, Alexey Zhuravlev <azhuravlev@....com>, Ted Tso <tytso@....edu>
Subject: Re: [PATCH] jbd2: Avoid long replay times due to high number or
 revoke blocks

On Fri 17-01-25 10:58:42, Zhang Yi wrote:
> On 2025/1/17 2:02, Jan Kara wrote:
> > Some users are reporting journal replay takes a long time when there is
> > excessive number of revoke blocks in the journal. Reported times are
> > like:
> > 
> > 1048576 records - 95 seconds
> > 2097152 records - 580 seconds
> > 
> > The problem is that hash chains in the revoke table gets excessively
> > long in these cases. Fix the problem by sizing the revoke table
> > appropriately before the revoke pass.
> > 
> > Thanks to Alexey Zhuravlev <azhuravlev@....com> for benchmarking the patch with
> > large numbers of revoke blocks [1].
> > 
> > [1] https://lore.kernel.org/all/20250113183107.7bfef7b6@x390.bzzz77.ru
> > 
> > Signed-off-by: Jan Kara <jack@...e.cz>
> 
> Hi, Jan,
> 
> This overall patch looks good to me; however, it appears to be not
> based on the latested version of the upstream kernel, and I have one
> minor suggestion below.

OK, will do.

> > @@ -874,14 +905,16 @@ static int do_one_pass(journal_t *journal,
> >  				need_check_commit_time = true;
> >  			}
> >  
> > -			/* If we aren't in the REVOKE pass, then we can
> > -			 * just skip over this block. */
> > -			if (pass != PASS_REVOKE) {
> > +			/*
> > +			 * If we aren't in the SCAN or REVOKE pass, then we can
> > +			 * just skip over this block.
> > +			 */
> > +			if (pass != PASS_REVOKE && pass != PASS_SCAN) {
> >  				brelse(bh);
> >  				continue;
> >  			}
> 
> How about move this code snippets to the beginning of the
> JBD2_REVOKE_BLOCK branch case?

I guess a good idea after the change. Thanks!

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