linux-kernel - Re: [PATCH RESEND v2 5/5] sbitmap: correct wake_batch recalculation to avoid potential IO hung

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Message-ID: <20230116095444.z77f6lvvxeys7zdi@quack3>
Date:   Mon, 16 Jan 2023 10:54:44 +0100
From:   Jan Kara <jack@...e.cz>
To:     Kemeng Shi <shikemeng@...weicloud.com>
Cc:     Yu Kuai <yukuai1@...weicloud.com>, Jan Kara <jack@...e.cz>,
        Ming Lei <ming.lei@...hat.com>,
        "yukuai (C)" <yukuai3@...wei.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        kbusch@...nel.org, Laibin Qiu <qiulaibin@...wei.com>
Subject: Re: [PATCH RESEND v2 5/5] sbitmap: correct wake_batch recalculation
 to avoid potential IO hung

On Mon 16-01-23 10:15:08, Kemeng Shi wrote:
> 
> 
> on 1/3/2023 10:12 AM, Kemeng Shi wrote:
> > Friendly ping...
> > 
> > on 12/26/2022 4:57 PM, Yu Kuai wrote:
> >> 在 2022/12/26 15:50, Yu Kuai 写道:
> >>
> >>>> why using
> >>>> wake batch of 4 is safe for cards with say 32 tags in case active_users is
> >>>> currently 32. Because I don't see why that is correct either.
> >>>>
> >>
> >> I see, you guys are worried that during the period that some hctx
> >> complete all it's not idle yet. It's right waiter might wait for
> >> other hctx to become idle to be awaken in this case. However, I'm
> >> not sure which way is better.
> >>
> >> Ming, do you have any idea?
> >>
> >> Thanks,
> >> Kuai
> >>
> > 
> Hi Jan. The magic batch 4 seems just for performance initially while
> lacks of full consideration. And there is no better solution provided
> in futher. Do you have any suggestion that I can do to make more
> progress.

Yeah, since there was not any good reasoning behind the magic batch of size
4, feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

to this patch.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR