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

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Message-ID: <x49lgu9s451.fsf@segfault.boston.devel.redhat.com>
Date:   Tue, 17 Jan 2017 17:39:06 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, 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

Jens Axboe <axboe@...nel.dk> writes:

> 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.

I had also considered bio_endio_notrace().

> - 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.

Hmm, okay.  I'll take a crack at that.

Thanks!
Jeff