linux-kernel - Re: [PATCH] f2fs: do decrease_sleep_time() if any of the victims have been selected

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Date:   Sun, 11 Dec 2022 20:30:12 +0800
From:   Yuwei Guan <ssawgyw@...il.com>
To:     Chao Yu <chao@...nel.org>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Yuwei.Guan@...krlife.com
Subject: Re: [PATCH] f2fs: do decrease_sleep_time() if any of the victims have
 been selected



在 2022/12/11 10:52, Chao Yu 写道:
> On 2022/12/9 19:28, Yuwei Guan wrote:
>> In non-foreground gc mode, if no victim is selected, the gc process
>> will wait for no_gc_sleep_time before waking up again. In this
>> subsequent time, even though a victim will be selected, the gc process
>> still waits for no_gc_sleep_time before waking up. The configuration
>> of wait_ms is not reasonable.
>>
>> After any of the victims have been selected, we need to do
>> decrease_sleep_time() to reduce wait_ms.
>>
>> If it is GC_URGENT_HIGH or GC_URGENT_MID gc mode,
>> wait_ms will keep urgent_sleep_time after executing 
>> decrease_sleep_time().
>>
>> In decrease_sleep_time() wait_time will be reduced to max_sleep_time
>> from no_gc_sleep_time, if *wait is no_gc_sleep_time. And then it goes
>> down in the next step.
>>
>> Signed-off-by: Yuwei Guan <Yuwei.Guan@...krlife.com>
>> ---
>>   fs/f2fs/gc.c | 2 ++
>>   fs/f2fs/gc.h | 7 ++++++-
>>   2 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index f0c6506d8975..c023ffeb9268 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -141,6 +141,8 @@ static int gc_thread_func(void *data)
>>               /* don't bother wait_ms by foreground gc */
>>               if (!foreground)
>>                   wait_ms = gc_th->no_gc_sleep_time;
>> +        } else {
>> +            decrease_sleep_time(gc_th, &wait_ms);
> 
> Once BGGC selects valid victim, it will go faster and fater?
> > How about:
> 
>      } else {
>          /* reset wait_ms to default sleep time */
>          if (wait_ms == gc_th->no_gc_sleep_time)
>              wait_ms = gc_th->min_sleep_time;
>      }
Indeed. it will go faster and fater, until wait_ms reduces to 
min_sleep_time. But your suggestion seems more reasonable, I will send 
it in v2 patch.
> 
> Thanks,
> 
>>           }
>>           if (foreground)
>> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
>> index 19b956c2d697..6402584dcd72 100644
>> --- a/fs/f2fs/gc.h
>> +++ b/fs/f2fs/gc.h
>> @@ -150,8 +150,13 @@ static inline void decrease_sleep_time(struct 
>> f2fs_gc_kthread *gc_th,
>>   {
>>       unsigned int min_time = gc_th->min_sleep_time;
>> -    if (*wait == gc_th->no_gc_sleep_time)
>> +    if (*wait == gc_th->urgent_sleep_time)
>> +        return;
>> +
>> +    if (*wait == gc_th->no_gc_sleep_time) {
>>           *wait = gc_th->max_sleep_time;
>> +        return;
>> +    }
>>       if ((long long)*wait - (long long)min_time < (long long)min_time)
>>           *wait = min_time;