kernel-packages team mailing list archive

[Launchpad Bug Tracker <1538040@xxxxxxxxxxxxxxxxxx>]

You have been subscribed to a public bug:

I have a brand new laptop (Asus N551VW, i7-6700HQ, 16 Gb ram) on which i
installed Ubuntu 14.04 64bit and a new Samsung SSD 850 PRO 512Gb (latest
firmware). I installed the default MySql 5.6.27 on the machine but I
noticed a very VERY slow performance of the database (just creating a db
and executing some migrations without any data takes around 33 seconds
while on lower-hardware co-workers notebooks it takes like 3 seconds).
Every sql statement seems to spend most time in "system lock" state, as
i could see with a SHOW PROCESSLIST.

I thought it to be an hard drive issue, but executing the hard drive
benchmark in Ubuntu gives 500 Mb/s read and 350 Mb/s write speed, which
looks mostly normal.

I also tried updating to the new 4.2 kernel, but the issue still there.
To make an experiment, i cloned the ssd on a normal hard drive, switched
it in and connected the SSD externally with an usb box. I moved mysql
data directory to the external disk, and retried the db creation: it
took only 2.5 seconds.

Just out of curiosity i tried the same operation on an internal non-ssd
disk: when the hd is plugged inside the laptop with sata, the database
creation takes more than 2 minutes, while with the data dir on external
usb (with the same physical disk) it took less than 10 seconds.

To make it short, after some research, adding barrier=0 to the mount
options of the root drive with no other modification caused the same
script to take 1.5 seconds instead of 33, with a 22x increase in
performance.

I have opened his bug on askubuntu (http://askubuntu.com/questions/725182/ssd-extremely-slow-when-connected-with-internal-sata-ok-with-external-usb ) and it was suggested that this coud be an issue of the controller firmware/driver.
The problem is present both in trusty's default kernel (3.19.0-47.53) and in the 4.2 (4.2.0-25.30).

Let me know if you need more informations!

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-4.2.0-25-generic 4.2.0-25.30~14.04.1
ProcVersionSignature: Ubuntu 4.2.0-25.30~14.04.1-generic 4.2.6
Uname: Linux 4.2.0-25-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
Date: Tue Jan 26 09:25:04 2016
InstallationDate: Installed on 2016-01-06 (19 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-lts-wily
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: linux (Ubuntu)
     Importance: Low
         Status: Incomplete


** Tags: amd64 apport-bug ext4 sata trusty
-- 
Internal Hard drive extremely slow unless using barrier=0 on ext4
https://bugs.launchpad.net/bugs/1538040
You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu.