From: Shaohua Li Date: Thu, 3 Dec 2009 11:58:05 +0000 (+0100) Subject: cfq-iosched: no dispatch limit for single queue X-Git-Tag: v2.6.33-rc1~379^2~39 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=474b18ccc264c472abeec50f48469b6477202699;p=pandora-kernel.git cfq-iosched: no dispatch limit for single queue Since commit 2f5cb7381b737e24c8046fd4aeab571fb71315f5, each queue can send up to 4 * 4 requests if only one queue exists. I wonder why we have such limit. Device supports tag can send more requests. For example, AHCI can send 31 requests. Test (direct aio randread) shows the limits reduce about 4% disk thoughput. On the other hand, since we send one request one time, if other queue pop when current is sending more than cfq_quantum requests, current queue will stop send requests soon after one request, so sounds there is no big latency. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- Reading git-diff-tree failed