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From: brookxu <brookxu.cn@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [PATCH v2] blk-throtl: optimize IOPS throttle for large IO scenarios
Date: Mon, 2 Aug 2021 09:30:29 +0800	[thread overview]
Message-ID: <c40d1fbf-30de-2325-a662-8fd08aa1b774@gmail.com> (raw)
In-Reply-To: <YQQjpQEBbdAgMUM7@mtj.duckdns.org>



Tejun Heo wrote on 2021/7/31 12:07 上午:
> On Fri, Jul 30, 2021 at 10:09:34AM +0800, brookxu wrote:
>>>> @@ -877,10 +900,19 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
>>>>  	else
>>>>  		tg->bytes_disp[rw] = 0;
>>>>  
>>>> -	if (tg->io_disp[rw] >= io_trim)
>>>> +	if (tg_io_disp(tg, rw) >= io_trim) {
>>>
>>> Instead of checking this in multiple places, would it be simpler to transfer
>>> the atomic counters to the existing counters whenever we enter blk-throtl
>>> and leave the rest of the code as-is?
>>
>> If we do this, we need to do similar processing on the bio submission path and the bio
>> resubmission path in pending_timer. It seems that the code is more complicated?
> 
> Yeah, basically whenever we enter blk-throtl. Factored to a function,
> calling it on entry should be fairly clean, right? I wonder whether it'd be
> better to consolidate all atomic counter handling in a single location and
> all it does is transferring whatever's accumulated to the usual counters.
> Also, when you're reading & resetting the atomic counters, can you use a
> pattern like the following?
> 
>   main_counter += atomic_xchg(counter, 0);
> 
> Right now, there's a race window between reading and resetting.

Yeah, thanks for your suggestion, I will submit the next version later.

> Thanks.
> 

      reply	other threads:[~2021-08-02  1:31 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28  9:01 brookxu
2021-07-29 17:11 ` Tejun Heo
2021-07-30  2:09   ` brookxu
2021-07-30 16:07     ` Tejun Heo
2021-08-02  1:30       ` brookxu [this message]

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