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

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Message-ID: <20170628165316.nozfbdvmpflqwt3f@kernel.org>
Date:   Wed, 28 Jun 2017 09:53:16 -0700
From:   Shaohua Li <shli@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        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 Wed, Jun 28, 2017 at 10:43:48AM -0600, Jens Axboe wrote:
> 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?

What's the best practice to do this without building errors? Ask Tejun
to merge the first 7 patches first?

Thanks,
Shaohua