[dm-devel] [PATCH 2/7] dm: add reserved_rq_based_ios module parameter
Mike Snitzer
snitzer at redhat.com
Thu Sep 12 23:15:31 UTC 2013
On Thu, Sep 12 2013 at 6:45pm -0400,
Mikulas Patocka <mpatocka at redhat.com> wrote:
> I think this is too complicated.
>
> dm-bufio uses similar approach like this patch - but in dm-bufio the code
> path is performance critical, we don't want to recalculate memory size
> with each i/o request.
>
> Here it is not performance critical, so I'd drop the mutex, drop the
> latch, drop the function __reserved_request_based_ios_refresh and add only
> these lines:
>
> pool_size = ACCESS_ONCE(reserved_rq_based_ios);
> if (!pool_size) pool_size = RESERVED_REQUEST_BASED_IOS;
Could be I'm missing something but isn't the locking about correctness
rather than performance?
Also, using the latch enables the dm_get_reserved_rq_based_ios()
interface that is used in patch 5.
Mike
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