linux-ext4 - Re: [PATCH] jbd2: Increase maximum transaction size

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Message-ID: <163ae0a0-f0c7-de10-0810-50b60c00651e@huawei.com>
Date: Tue, 2 Jul 2024 16:48:12 +0800
From: Zhang Yi <yi.zhang@...wei.com>
To: Jan Kara <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, Ted Tso <tytso@....edu>
Subject: Re: [PATCH] jbd2: Increase maximum transaction size

On 2024/7/1 21:28, Jan Kara wrote:
> Originally, we were quite conservative in limiting maximum transaction
> size to a quarter of the journal because we were not accounting
> transaction descriptor and revoke blocks. These days we do properly
> account them and reserve space for them from the total transaction
> credits. Thus there's no need to be so conservative and we can increase
> the maximum transaction size to one third of the journal (even half
> should work fine in principle but the performance will likely suffer in
> that case). This also fixes failures to grow filesystems with tiny
> journals.
> 

This looks straightforward and reasonable to me. I've done some metadata
intensive performance tests with fs_mark, no obvious degradation and
fluctuation has been found.

Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

Thanks,
Yi.

> Link: CA+hUFcuGs04JHZ_WzA1zGN57+ehL2qmHOt5a7RMpo+rv6Vyxtw@...l.gmail.com
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  include/linux/jbd2.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index ab04c1c27fae..7273ef1732bf 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1662,7 +1662,7 @@ int jbd2_fc_release_bufs(journal_t *journal);
>  
>  static inline int jbd2_journal_get_max_txn_bufs(journal_t *journal)
>  {
> -	return (journal->j_total_len - journal->j_fc_wbufsize) / 4;
> +	return (journal->j_total_len - journal->j_fc_wbufsize) / 3;
>  }
>  
>  /*
>