linux-kernel - Re: [PATCH for linux-next] mm/page-writeback.c: make changes of dirty_writeback

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Date:   Sat, 14 Oct 2017 19:59:06 +0200
From:   Damian Tometzki <damian.tometzki@...oud.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     axboe@...nel.dk, akpm@...ux-foundation.org, jack@...e.cz,
        hannes@...xchg.org, vdavydov.dev@...il.com, jlayton@...hat.com,
        nborisov@...e.com, tytso@....edu, yamada.masahiro@...ionext.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH for linux-next] mm/page-writeback.c: make changes of
 dirty_writeback_centisecs take effect immediately

On Sat, 14. Oct 16:38, Yafang Shao wrote:
> This patch is the followup of the prvious patch:
> [writeback: schedule periodic writeback with sysctl].
> 
> There's another issue to fix.
> For example,
> - When the tunable was set to one hour and is reset to one second, the
>   new setting will not take effect for up to one hour.
> 
> Kicking the flusher threads immediately fixes it.
> 
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
>  mm/page-writeback.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 3969e69..768fe4e 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1978,7 +1978,16 @@ int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
>  	int ret;
>  
>  	ret = proc_dointvec(table, write, buffer, length, ppos);
> -	if (!ret && !old_interval && dirty_writeback_interval)
> +
> +	/*
> +	 * Writing 0 to dirty_writeback_interval will disable periodic writeback
> +	 * and a different non-zero value will wakeup the writeback threads.
> +	 * wb_wakeup_delayed() would be more appropriate, but it's a pain to
> +	 * iterate over all bdis and wbs.
> +	 * The reason we do this is to make the change take effect immediately.
> +	 */
> +	if (!ret && write && dirty_writeback_interval &&
> +		dirty_writeback_interval != old_interval)
>  		wakeup_flusher_threads(WB_REASON_PERIODIC);
Is that call right ? The call need two arguments ?
--> wakeup_flusher_threads(0,WB_REASON_PERIODIC);

best regards
Damian

>  
>  	return ret;
> -- 
> 1.8.3.1
> 
> --
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