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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: Thu, 29 Sep 2022 19:14:23 +0300	[thread overview]
Message-ID: <1b7feff8-48a4-6cd2-5a44-28a499630132@grimberg.me> (raw)
In-Reply-To: <YzWzvOKgoAqltAA0@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.
> 
> Instead of duplicating the accounting, could you just have the stats file report
> the sum of its hidden devices?

Interesting...

How do you suggest we do that? .collect_stats() callout in fops?

  reply	other threads:[~2022-09-29 16:14 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 [this message]
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
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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