Re: [PATCH] Block: initialize bio_cnt_ret_time for the first time

Jens Axboe
2018-06-29T20:26:07Z

On 6/29/18 2:23 PM, Liu Bo wrote:
> On Fri, Jun 29, 2018 at 02:00:01PM -0600, Jens Axboe wrote:
>> On 6/20/18 9:07 PM, Liu Bo wrote:
>>> When a new tg is created, tg->bio_cnt_ret_time is 0, so if the first
>>> IO going thru this tg turns out to be a bad one, we fail to record it
>>> in tg->bad_bio_cnt as
>>>
>>> if (jiffies > bio_cnt_ret_time) {
>>> tg->bad_bio_cnt /= 2;
>>> }
>>
>> Shouldn't we rather ensure that ->bio_cnt_ret_time is initialized to
>> jiffies?
>>
>
> Indeed, it's what the patch does, i.e. initialize tg->bio_cnt_reset_time to
> jiffies on the first use.

You do it on the first use, on the hot path, presumable. My suggestion
was to do it when tg is instantiated instead. From a quick look, that
would appear to be in throtl_pd_alloc().

--
Jens Axboe