linux-kernel - Re: [PATCH V4 00/12] blktrace: output cgroup info

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Message-ID: <f458724a-464b-6039-4893-a2584540044d@kernel.dk>
Date:   Wed, 28 Jun 2017 10:43:48 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Shaohua Li <shli@...nel.org>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org
Cc:     tj@...nel.org, gregkh@...uxfoundation.org, hch@....de,
        rostedt@...dmis.org, lizefan@...wei.com, Kernel-team@...com,
        Shaohua Li <shli@...com>
Subject: Re: [PATCH V4 00/12] blktrace: output cgroup info

On 06/28/2017 10:29 AM, Shaohua Li wrote:
> From: Shaohua Li <shli@...com>
> 
> Hi,
> 
> Currently blktrace isn't cgroup aware. blktrace prints out task name of current
> context, but the task of current context isn't always in the cgroup where the
> BIO comes from. We can't use task name to find out IO cgroup. For example,
> Writeback BIOs always comes from flusher thread but the BIOs are for different
> blk cgroups. Request could be requeued and dispatched from completely different
> tasks. MD/DM are another examples. This brings challenges if we want to use
> blktrace for performance tunning with cgroup enabled.
> 
> This patchset try to fix the gap. We print out cgroup fhandle info in blktrace.
> Userspace can use open_by_handle_at() syscall to find the cgroup by fhandle. Or
> userspace can use name_to_handle_at() syscall to find fhandle for a cgroup and
> use a BPF program to filter out blktrace for a specific cgroup.
> 
> The first 6 patches adds export operation handlers for kernfs, so userspace can
> use open_by_handle_at/name_to_handle_at to a kernfs file. Later patches make
> blktrace output cgroup info.

Series looks fine to me. I don't know how you want to split or funnel it,
since it touches multiple different parts. Would it make sense to split this
series into two - one for the kernfs changes, and then a subsequent block
series that depend on that?

-- 
Jens Axboe