linux-kernel - Re: [patch] block: add blktrace C events for bio-based drivers

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Date:   Tue, 17 Jan 2017 14:07:32 -0800
From:   Jens Axboe <axboe@...nel.dk>
To:     Jeff Moyer <jmoyer@...hat.com>, linux-block@...r.kernel.org
Cc:     agk@...hat.com, snitzer@...hat.com, dm-devel@...hat.com,
        shli@...nel.org, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, hch@....de
Subject: Re: [patch] block: add blktrace C events for bio-based drivers

On 01/17/2017 01:57 PM, Jeff Moyer wrote:
> Only a few bio-based drivers actually generate blktrace completion
> (C) events.  Instead of changing all bio-based drivers to call
> trace_block_bio_complete, move the tracing to bio_complete, and remove
> the explicit tracing from the few drivers that actually do it.  After
> this patch, there is exactly one caller of trace_block_bio_complete
> and one caller of trace_block_rq_complete.  More importantly, all
> bio-based drivers now generate C events, which is useful for
> performance analysis.

I like the change, hate the naming. I'd prefer one of two things:

- Add bio_endio_complete() instead. That name sucks too, the
  important part is flipping the __name() to have a trace
  version instead.

- Mark the bio as trace completed, and keep the naming. Since
  it's only off the completion path, that can be just marking
  the bi_flags non-atomically.

I probably prefer the latter.

-- 
Jens Axboe