Re: [PATCH 1/4] block: add scalable completion tracking of requests

From: Jens Axboe
Date: Wed Nov 02 2016 - 10:55:41 EST

On 11/02/2016 08:52 AM, Christoph Hellwig wrote:
On Tue, Nov 01, 2016 at 03:05:22PM -0600, Jens Axboe wrote:
For legacy block, we simply track them in the request queue. For
blk-mq, we track them on a per-sw queue basis, which we can then
sum up through the hardware queues and finally to a per device

what is the use case for the legacy request tracking?

Buffered writeback code uses the same base. Additionally, it could
replace some user space tracking for latency outliers that people are
currently running.

Jens Axboe