From: Paolo Valente <paolo.valente@linaro.org>
To: Mike Galbraith <efault@gmx.de>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
linux-block <linux-block@vger.kernel.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Oleksandr Natalenko <oleksandr@natalenko.name>
Subject: Re: bug in tag handling in blk-mq?
Date: Wed, 9 May 2018 07:06:31 +0200 [thread overview]
Message-ID: <511C7624-6089-44E2-840A-E2657141AD88@linaro.org> (raw)
In-Reply-To: <1525839089.15732.1.camel@gmx.de>
> Il giorno 09 mag 2018, alle ore 06:11, Mike Galbraith <efault@gmx.de> ha scritto:
>
> On Tue, 2018-05-08 at 19:09 -0600, Jens Axboe wrote:
>>
>> Alright, I managed to reproduce it. What I think is happening is that
>> BFQ is limiting the inflight case to something less than the wake
>> batch for sbitmap, which can lead to stalls. I don't have time to test
>> this tonight, but perhaps you can give it a go when you are back at it.
>> If not, I'll try tomorrow morning.
>>
>> If this is the issue, I can turn it into a real patch. This is just to
>> confirm that the issue goes away with the below.
>
> Confirmed. Impressive high speed bug stomping.
>
Great! It's a real relief that this ghost is gone.
Thank you both,
Paolo
>> diff --git a/lib/sbitmap.c b/lib/sbitmap.c
>> index e6a9c06ec70c..94ced15b6428 100644
>> --- a/lib/sbitmap.c
>> +++ b/lib/sbitmap.c
>> @@ -272,6 +272,7 @@ EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
>>
>> static unsigned int sbq_calc_wake_batch(unsigned int depth)
>> {
>> +#if 0
>> unsigned int wake_batch;
>>
>> /*
>> @@ -284,6 +285,9 @@ static unsigned int sbq_calc_wake_batch(unsigned int depth)
>> wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
>>
>> return wake_batch;
>> +#else
>> + return 1;
>> +#endif
>> }
>>
>> int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
>>
next prev parent reply other threads:[~2018-05-09 5:06 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-07 14:03 bug in tag handling in blk-mq? Paolo Valente
2018-05-07 16:39 ` Jens Axboe
2018-05-07 18:02 ` Paolo Valente
2018-05-08 4:51 ` Mike Galbraith
2018-05-08 8:37 ` Mike Galbraith
2018-05-08 14:55 ` Jens Axboe
2018-05-08 16:42 ` Mike Galbraith
2018-05-08 20:37 ` Jens Axboe
2018-05-08 21:19 ` Jens Axboe
2018-05-09 1:09 ` Jens Axboe
2018-05-09 4:11 ` Mike Galbraith
2018-05-09 5:06 ` Paolo Valente [this message]
2018-05-09 15:18 ` Jens Axboe
2018-05-09 16:57 ` Mike Galbraith
2018-05-09 17:01 ` Jens Axboe
2018-05-09 18:31 ` Mike Galbraith
2018-05-09 19:50 ` Jens Axboe
2018-05-10 4:38 ` Mike Galbraith
2018-05-09 5:09 ` Mike Galbraith
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