From: Chong Yuan <chong.yuan@memblaze.com>
Date: Wed, 15 Apr 2015 17:39:29 +0000 (-0600)
Subject: blk-mq: reduce unnecessary software queue looping
X-Git-Tag: omap-for-v4.2/o2_dc~109^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=889fa31f00b2;p=pandora-kernel.git

blk-mq: reduce unnecessary software queue looping

In flush_busy_ctxs() and blk_mq_hctx_has_pending(), regardless of how many
ctxs assigned to one hctx, they will all loop hctx->ctx_map.map_size
times. Here hctx->ctx_map.map_size is a const ALIGN(nr_cpu_ids, 8) / 8.
Especially, flush_busy_ctxs() is in hot code path. And it's unnecessary.
Change ->map_size to contain the actually mapped software queues, so we
only loop for as many iterations as we have to.

And remove cpumask setting and nr_ctx count in blk_mq_init_cpu_queues()
since they are all re-done in blk_mq_map_swqueue().
blk_mq_map_swqueue().

Signed-off-by: Chong Yuan <chong.yuan@memblaze.com>
Reviewed-by: Wenbo Wang <wenbo.wang@memblaze.com>

Updated by me for formatting and commenting.

Signed-off-by: Jens Axboe <axboe@fb.com>
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