From: Steven Davies <btrfs-list@steev.me.uk>
To: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 1/3] btrfs: add readmirror type framework
Date: Thu, 2 Jan 2020 19:32:44 +0000 [thread overview]
Message-ID: <4f4a1dab-fd9b-a5b6-2109-d82fc222d208@steev.me.uk> (raw)
In-Reply-To: <1577959968-19427-2-git-send-email-anand.jain@oracle.com>
On 02/01/2020 10:12, Anand Jain wrote:
> As of now we use %pid method to read stripped mirrored data. So
> application's process id determines the stripe id to be read. This type
> of read IO routing typically helps in a system with many small
> independent applications tying to read random data. On the other hand
> the %pid based read IO distribution policy is inefficient if there is a
> single application trying to read large data and the overall disk
> bandwidth remains under utilized.
>
> So this patch introduces a framework where we could add more readmirror
> policies, such as routing the IO based on device's wait-queue or manual
> when we have a read-preferred device or a policy based on the target
> storage caching.
I think the idea is good but that it would be cleaner if the tunable was
named read_policy rather than readmirror as it's more obvious that it
contains a policy tunable.
Do you envisage allowing more than one policy to be active for a
filesystem? If not, what about using the same structure as the CPU
frequency and block IO schedulers with the format
#cat /sys/block/sda/queue/scheduler
noop [deadline] cfq
Such that btrfs would (eventually) have something like
#cat /sys/fs/btrfs/UUID/read_policy
by_pid [user_defined_device] by_shortest_queue
And the policy would be changed by echo'ing the new policy name to the
read_policy kobject.
Steve
next prev parent reply other threads:[~2020-01-02 19:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-02 10:12 [PATCH v2 0/3] readmirror feature (sysfs and in-memory only approach) Anand Jain
2020-01-02 10:12 ` [PATCH v2 1/3] btrfs: add readmirror type framework Anand Jain
2020-01-02 16:24 ` Josef Bacik
2020-01-03 9:57 ` Anand Jain
2020-01-02 19:32 ` Steven Davies [this message]
2020-01-03 10:28 ` Anand Jain
2020-01-03 14:51 ` Steven Davies
2020-01-03 10:31 ` [PATCH v3 " Anand Jain
2020-01-02 10:12 ` [PATCH v2 2/3] btrfs: sysfs, add readmirror kobject Anand Jain
2020-01-02 10:12 ` [PATCH v2 3/3] btrfs: sysfs, create by_pid readmirror attribute Anand Jain
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