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 10:52:20 +0800
From:   Chao Yu <chao@...nel.org>
To:     Yuwei Guan <ssawgyw@...il.com>, 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

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;
	}

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;