lkml.org 
[lkml]   [2022]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH -next RFC v2 4/8] blk-mq: don't preempt tag under heavy load
From
Date
在 2022/04/08 22:24, Bart Van Assche 写道:
> On 4/8/22 00:39, Yu Kuai wrote:
>> The idle way to disable tag preemption is to track how many tags are
>
> idle -> ideal?
>
>> available, and wait directly in blk_mq_get_tag() if free tags are
>> very little. However, this is out of reality because fast path is
>> affected.
>>
>> As 'ws_active' is only updated in slow path, this patch disable tag
>> preemption if 'ws_active' is greater than 8, which means there are many
>> threads waiting for tags already.
>>
>> Once tag preemption is disabled, there is a situation that can cause
>> performance degration(or io hung in extreme scenarios): the waitqueue
>
> degration -> degradation?
>
>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>> index 2615bd58bad3..b49b20e11350 100644
>> --- a/block/blk-mq.h
>> +++ b/block/blk-mq.h
>> @@ -156,6 +156,7 @@ struct blk_mq_alloc_data {
>>       /* allocate multiple requests/tags in one go */
>>       unsigned int nr_tags;
>> +    bool preemption;
>>       struct request **cached_rq;
>
> Please change "preemption" into "preempt".

Thanks for your advice, will change that and previous spelling mistakes.

Kuai
>
> Thanks,
>
> Bart.
>
> .
>

\
 
 \ /
  Last update: 2022-04-09 04:38    [W:0.043 / U:0.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site