linux-ext4 - Re: [PATCH] jbd2: use rhashtable for revoke records during replay

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Message-ID: <bf2vn7ggijrmjixtspmp6u3fgjzzlgjfnyra32hnggulpuncbb@4lqbgrk3rgup>
Date: Thu, 16 Jan 2025 18:59:13 +0100
From: Jan Kara <jack@...e.cz>
To: Alexey Zhuravlev <azhuravlev@....com>
Cc: Li Dongyang <dongyangli@....com>, linux-ext4@...r.kernel.org, 
	Andreas Dilger <adilger@...ger.ca>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] jbd2: use rhashtable for revoke records during replay

On Mon 13-01-25 18:31:07, Alexey Zhuravlev wrote:
> Hi,
> 
> I benchmarked rhashtable based patch vs Jan's patch:
> 
> records		vanilla	rhashtable	JK patch
> 2.5M records	102s	29s		25s
> 5.0M records	317s	28s		30s
> 6.0M records	--	35s		44s
> 
> the tests were done using 4.18 kernel (I guess this doesn't matter much
> in this context), using an SSD.  time to mount after a crash (simulated
> with read-only device mapper) was measured.  unfortunately I wasn't able
> to reproduce with more records as my test node has just 32GB RAM,

Thanks for performing the tests! So I guess the dynamic sizing of revoke
table before replay is indeed good enough. Let me do a proper patch
submission.

								Honza

> 
> 
> thanks, Alex
> 
> 
> On Mon, 4 Nov 2024 20:05:50 +1100
> Li Dongyang <dongyangli@....com> wrote:
> 
> > Resizable hashtable should improve journal replay time when
> > we have million of revoke records.
> > Notice that rhashtable is used during replay only,
> > as removal with list_del() is less expensive and it's still used
> > during regular processing.
> > 
> > before:
> > 1048576 records - 95 seconds
> > 2097152 records - 580 seconds
> > 
> > after:
> > 1048576 records - 2 seconds
> > 2097152 records - 3 seconds
> > 4194304 records - 7 seconds
> > 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR