From: Joe Thornber <ejt@redhat.com>
Date: Fri, 12 Sep 2014 10:34:01 +0000 (+0100)
Subject: dm thin: performance improvement to discard processing
X-Git-Tag: omap-for-v3.19/fixes-for-merge-window~22^2~38
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7a7e97ca580b944d2c89b59bc74a7b9ddd044705;p=pandora-kernel.git

dm thin: performance improvement to discard processing

When processing a discard bio, if the block is already quiesced do the
discard immediately rather than adding the mapping to a list for the
next iteration of the worker thread.

Discarding a fully provisioned 100G thin volume with 64k block size goes
from 860s to 95s with this change.

Clearly there's something wrong with the worker architecture, more
investigation needed.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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