Messages in this thread | | | Subject | Re: [PATCH -next 4/5] blk-iocost: bypass if only one cgroup issues io | From | Yu Kuai <> | Date | Wed, 12 Oct 2022 09:33:46 +0800 |
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Hi, Tejun!
在 2022/10/12 1:02, Tejun Heo 写道: > On Tue, Oct 11, 2022 at 04:35:46PM +0800, Yu Kuai wrote: >> From: Yu Kuai <yukuai3@huawei.com> >> >> In this special case, there is no need to throttle io. >> >> Signed-off-by: Yu Kuai <yukuai3@huawei.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?
Yes, you're right, this patch doesn't look good in this case.
The reason why I tried to do this is because during test, I found that io performance is affected when I only issue io from one cgroup(only happened in some environment with default configuration), and I found out that each io is throttled for some time before dispatching.
Perhaps a suitable configuration can avoid this problem.
Thanks, Kuai
> > Thanks. >
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