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From: Bart Van Assche <bvanassche@acm.org>
To: Damien Le Moal <Damien.LeMoal@wdc.com>, Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>, Jaegeuk Kim <jaegeuk@kernel.org>,
	Niklas Cassel <Niklas.Cassel@wdc.com>,
	Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 3/4] block/mq-deadline: Stop using per-CPU counters
Date: Fri, 24 Sep 2021 19:59:22 -0700	[thread overview]
Message-ID: <81cd7cea-6060-4500-8af3-cd324aef61de@acm.org> (raw)
In-Reply-To: <DM6PR04MB7081B7096944F8115A8BE2B6E7A49@DM6PR04MB7081.namprd04.prod.outlook.com>

On 9/24/21 03:58, Damien Le Moal wrote:
> On 2021/09/24 8:27, Bart Van Assche wrote:
>> -/* I/O statistics for all I/O priorities (enum dd_prio). */
>> -struct io_stats {
>> -	struct io_stats_per_prio stats[DD_PRIO_COUNT];
>> +	uint32_t inserted;
>> +	uint32_t merged;
>> +	uint32_t dispatched;
>> +	atomic_t completed;
> 
> Why not use 64-bits types (regular unsigned long long and atomic64_t) ?

Even 64-bit counters can overflow. Using 32-bit counters makes it easier to
trigger an overflow of these counters.

Thanks,

Bart.

  reply	other threads:[~2021-09-25  2:59 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-23 23:23 [PATCH 0/4] Restore I/O priority support in the mq-deadline scheduler Bart Van Assche
2021-09-23 23:26 ` [PATCH 1/4] block/mq-deadline: Improve request accounting further Bart Van Assche
2021-09-23 23:26   ` [PATCH 2/4] block/mq-deadline: Add an invariant check Bart Van Assche
2021-09-24 10:54     ` Damien Le Moal
2021-09-27 15:53     ` Niklas Cassel
2021-09-23 23:26   ` [PATCH 3/4] block/mq-deadline: Stop using per-CPU counters Bart Van Assche
2021-09-24 10:58     ` Damien Le Moal
2021-09-25  2:59       ` Bart Van Assche [this message]
2021-09-27  0:19         ` Damien Le Moal
2021-09-27  2:38           ` Bart Van Assche
2021-09-27  3:41             ` Damien Le Moal
2021-09-27 15:53     ` Niklas Cassel
2021-09-23 23:26   ` [PATCH 4/4] block/mq-deadline: Prioritize high-priority requests Bart Van Assche
2021-09-24 11:08     ` Damien Le Moal
2021-09-27 20:03       ` Bart Van Assche
2021-09-24 10:54   ` [PATCH 1/4] block/mq-deadline: Improve request accounting further Damien Le Moal
2021-09-27 15:53   ` Niklas Cassel

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