From: Sagi Grimberg <sagi@grimberg.me>
To: Keith Busch <kbusch@kernel.org>
Cc: Max Gurtovoy <mgurtovoy@nvidia.com>,
linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH rfc] nvme: support io stats on the mpath device
Date: Mon, 3 Oct 2022 11:02:30 +0300 [thread overview]
Message-ID: <cef09c04-17d6-c588-be9f-b33e36dfce1a@grimberg.me> (raw)
In-Reply-To: <YzcINzNpZ+4zkupd@kbusch-mbp.dhcp.thefacebook.com>
>>>>> 3. Do you have some performance numbers (we're touching the fast path
>>>>> here) ?
>>>>
>>>> This is pretty light-weight, accounting is per-cpu and only wrapped by
>>>> preemption disable. This is a very small price to pay for what we gain.
>>>
>>> It does add up, though, and some environments disable stats to skip the
>>> overhead. At a minimum, you need to add a check for blk_queue_io_stat() before
>>> assuming you need to account for stats.
>>
>> But QUEUE_FLAG_IO_STAT is set by nvme-mpath itself?
>> You mean disable IO stats in runtime?
>
> Yes, the user can disable it at any time. That actually makes things a bit
> tricky since it can be enabled at the start of an IO and disabled by the time
> it completes.
That is what blk_do_io_stat is for, we can definitely export that.
next prev parent reply other threads:[~2022-10-03 8:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 19:55 [PATCH rfc 0/1] nvme-mpath: Add IO stats support Sagi Grimberg
2022-09-28 19:55 ` [PATCH rfc] nvme: support io stats on the mpath device Sagi Grimberg
2022-09-29 9:42 ` Max Gurtovoy
2022-09-29 9:59 ` Sagi Grimberg
2022-09-29 10:25 ` Max Gurtovoy
2022-09-29 15:03 ` Keith Busch
2022-09-29 16:14 ` Sagi Grimberg
2022-09-30 15:21 ` Keith Busch
2022-10-03 8:09 ` Sagi Grimberg
2022-10-25 15:30 ` Christoph Hellwig
2022-10-25 15:58 ` Sagi Grimberg
2022-10-30 16:22 ` Christoph Hellwig
2022-09-29 16:32 ` Sagi Grimberg
2022-09-30 15:16 ` Keith Busch
2022-10-03 8:02 ` Sagi Grimberg [this message]
2022-10-03 9:32 ` Sagi Grimberg
2022-09-29 15:05 ` Jens Axboe
2022-09-29 16:25 ` Sagi Grimberg
2022-09-30 0:08 ` Jens Axboe
2022-10-03 8:35 ` Sagi Grimberg
2022-09-29 10:04 ` Sagi Grimberg
2022-09-29 15:07 ` Jens Axboe
2022-10-03 8:38 ` Sagi Grimberg
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