On 04/23/2014 01:11 AM, Dan Williams wrote:
On Mon, Apr 21, 2014 at 12:29 AM, Jet Chen <jet.chen(a)intel.com>
> HI Dan,
> we noticed the below changes on
> commit 8a4aeec8d2d6a3edeffbdfae451cdf05cbf0fefd ("libata/ahci: accommodate
> tag ordered controllers")
Hi, was this on simulated hardware or a real AHCI controller and disk?
Testing was on a physical machine with a real AHCI controller.
root@bay ~# lspci | grep AHCI
00:1f.2 SATA controller: Intel Corporation 82801IR/IO/IH (ICH9R/DO/DH) 6 port SATA
Controller [AHCI mode] (rev 02)
It does appear this test noticed increased throughput:
203893 ~ 0% +3.7% 211474 ~ 0% TOTAL iostat.sda.wkB/s
I wonder if ap->last_tag can be moved to a hotter cacheline, but if
throughput goes up I can imagine it throws off the cpu statistics
quite a bit.