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Message-ID: <Y0WhpuqK/8CEZAGc@slm.duckdns.org>
Date: Tue, 11 Oct 2022 07:02:30 -1000
From: Tejun Heo <tj@...nel.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, yukuai3@...wei.com,
yi.zhang@...wei.com
Subject: Re: [PATCH -next 4/5] blk-iocost: bypass if only one cgroup issues io
On Tue, Oct 11, 2022 at 04:35:46PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
>
> In this special case, there is no need to throttle io.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
> block/blk-iocost.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-iocost.c b/block/blk-iocost.c
> index 5acc5f13bbd6..32e7e416d67c 100644
> --- a/block/blk-iocost.c
> +++ b/block/blk-iocost.c
> @@ -2564,8 +2564,13 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
> bool use_debt, ioc_locked;
> unsigned long flags;
>
> - /* bypass IOs if disabled, still initializing, or for root cgroup */
> - if (!ioc->enabled || !iocg || !iocg->level)
> + /*
> + * bypass IOs if disabled, still initializing, for root cgroup,
> + * or the cgroup is the only cgroup with io.
> + */
> + if (!ioc->enabled || !iocg || !iocg->level ||
> + (iocg->hweight_inuse == WEIGHT_ONE &&
> + atomic_read(&ioc->hweight_gen) == iocg->hweight_gen))
I'm not sure about this one. Bypassing here means that we lose track of how
much IO it's issuing which can affect future throttling decisions, right?
Thanks.
--
tejun
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