Re: [RFC] add sysfs to dynamically control blk request tagmaintenance

[Arjan van de Ven]

On Fri, 2005-10-07 at 09:41 +0200, Jens Axboe wrote:
> Ok that makes more sense! But it's a little worrying that
> blk_queue_end_tag() would show up as hot in the profile, it is actually
> quite lean.

it probably just is the first one to touch the IO structures after the
completion, and thus gets the penalty for the cachemiss. Something has
to have that after io completion (the io started usually > 10 msec ago
after all, and usually on another cpu at that) and my experience is that
it's one of those jello elephants; you can only move it around but not
really avoid it.


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