From: Christoph Hellwig <hch@infradead.org>
To: Keith Busch <kbusch@kernel.org>
Cc: "Ewan D. Milne" <emilne@redhat.com>,
linux-nvme@lists.infradead.org, tsong@purestorage.com
Subject: Re: [PATCH 2/3] nvme: multipath: only update ctrl->nr_active when using queue-depth iopolicy
Date: Wed, 8 Nov 2023 00:09:33 -0800 [thread overview]
Message-ID: <ZUtCPeDYRaGszXnE@infradead.org> (raw)
In-Reply-To: <ZUqx7JoyPG1QxYeY@kbusch-mbp.dhcp.thefacebook.com>
On Tue, Nov 07, 2023 at 02:53:48PM -0700, Keith Busch wrote:
> On Tue, Nov 07, 2023 at 04:23:30PM -0500, Ewan D. Milne wrote:
> > The atomic updates of ctrl->nr_active are unnecessary when using
> > numa or round-robin iopolicy, so avoid that cost on a per-request basis.
> > Clear nr_active when changing iopolicy and do not decrement below zero.
> > (This handles changing the iopolicy while requests are in flight.)
>
> Oh, here's restricting it to that policy. Any reason not to fold it in
> the first one?
It should, and I agree with all the other comments.
But I'm also pretty deeply unhappy with the whole thing. This is a
controller-wise atomic taken for every I/O. How slow are the subsystems
people want to use it for? And is a global max active really the
right measure, or would e a per-cpu, or at least batched per-cpu as
used by the percpu counters by a better option?
next prev parent reply other threads:[~2023-11-08 8:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-07 21:23 [PATCH 1/3] nvme: multipath: Implemented new iopolicy "queue-depth" Ewan D. Milne
2023-11-07 21:23 ` [PATCH 2/3] nvme: multipath: only update ctrl->nr_active when using queue-depth iopolicy Ewan D. Milne
2023-11-07 21:42 ` Chaitanya Kulkarni
2023-11-07 21:53 ` Keith Busch
2023-11-07 22:03 ` Ewan Milne
2023-11-08 8:09 ` Christoph Hellwig [this message]
2023-11-08 16:58 ` John Meneghini
2023-11-08 18:38 ` Ewan Milne
2023-11-10 1:18 ` Uday Shankar
2023-11-13 21:16 ` Ewan Milne
2023-11-07 21:23 ` [PATCH 3/3] nvme: multipath: Invalidate current_path when changing iopolicy Ewan D. Milne
2023-11-08 8:10 ` Christoph Hellwig
2023-11-07 21:40 ` [PATCH 1/3] nvme: multipath: Implemented new iopolicy "queue-depth" Chaitanya Kulkarni
2023-11-07 21:46 ` Chaitanya Kulkarni
2023-11-07 21:56 ` Ewan Milne
2023-11-07 23:32 ` John Meneghini
2023-11-08 4:14 ` Chaitanya Kulkarni
2023-11-07 21:49 ` Keith Busch
2023-11-07 22:01 ` Ewan Milne
2023-11-07 22:14 ` Keith Busch
2024-05-09 20:29 ` [PATCH v2 0/3] nvme: queue-depth multipath iopolicy John Meneghini
2024-05-09 20:29 ` [PATCH v2 1/3] nvme: multipath: Implemented new iopolicy "queue-depth" John Meneghini
2024-05-09 20:29 ` [PATCH v2 2/3] nvme: multipath: only update ctrl->nr_active when using queue-depth iopolicy John Meneghini
2024-05-09 20:29 ` [PATCH v2 3/3] nvme: multipath: Invalidate current_path when changing iopolicy John Meneghini
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