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

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Message-ID: <b088d7e7-bda9-186d-9334-12f16aa92463@kernel.dk>
Date:   Sat, 14 Oct 2017 14:19:34 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Damian Tometzki <damian.tometzki@...oud.com>,
        Yafang Shao <laoar.shao@...il.com>
Cc:     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 10/14/2017 11:59 AM, Damian Tometzki wrote:
> 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);

It's right, the nr_pages argument was killed.

-- 
Jens Axboe