High write latency on Intel Pro 1500 SSD

[SDoni]

Hello!

I recently upgraded my laptop with a brand new Intel Pro 1500 SSD (180 GB). While trying out various measurements using Linux tools - I'm a performance addict - I discovered something interesting.

I've recorded some IO operations (mostly write sync) with latency of about 170 ms ! I couldn't believe it: an SSD 1 OOM slower than an HDD?

Workload: normal working sessions, no stress at all. OS is Ubuntu 14.04 (trim enabled by default via a crontab weekly job), application running were Chromium browser and a Win 7 KVM VM with MS office open. Filling status:

$ df -h

Filesystem Size Used Avail Use% Mounted on

/dev/sda5 101G 71G 25G 74% /

none 4,0K 0 4,0K 0% /sys/fs/cgroup

udev 3,8G 4,0K 3,8G 1% /dev

tmpfs 768M 1,3M 767M 1% /run

none 5,0M 0 5,0M 0% /run/lock

none 3,8G 38M 3,8G 1% /run/shm

none 100M 68K 100M 1% /run/user

/dev/sda2 57G 33G 24G 58% /media/ste/Windows7_OS

Here is an example of the latency data, which I recorded and confirmed with multiple tools: Brendan Gregg ftrace scripts (https://github.com/brendangregg/perf-tools brendangregg/perf-tools · GitHub), blktrace/blkparse/btt, iostat -x 1.

Example:

sudo ./iolatency:

>=(ms) .. <(ms) : I/O |Distribution |

0 -> 1 : 0 | |

1 -> 2 : 0 | |

2 -> 4 : 0 | |

4 -> 8 : 1 |# |

8 -> 16 : 1 |# |

16 -> 32 : 0 | |

32 -> 64 : 0 | |

64 -> 128 : 0 | |

128 -> 256 : 32 |# |

sudo ./iosnoop:

Tracing block I/O. Ctrl-C to end.

COMM PID TYPE DEV BLOCK BYTES LATms

jbd2/sda5-166 166 WS 8,0 227094344 53248 177.84

0 WS 8,0 227094448 4096 2.02

kworker/u16:0 20402 W 8,0 178377528 4096 175.48

kworker/u16:0 20402 W 8,0 178377472 4096 175.46

kworker/u16:0 20402 W 8,0 230578432 4096 175.46

kworker/u16:0 20402 W 8,0 178377696 4096 175.50

kworker/u16:0 20402 W 8,0 230431976 4096 176.35

kworker/u16:0 20402 W 8,0 230409184 4096 176.36

kworker/u16:0 20402 W 8,0 121944064 4096 178.21

kworker/u16:0 20402 WM 8,0 121944088 4096 178.24

kworker/u16:0 20402 WM 8,0 121944112 4096 178.24

kworker/u16:0 20402 WM 8,0 159693064 4096 178.79

kworker/u16:0 20402 WM 8,0 205830272 4096 178.81

kworker/u16:0 20402 WM 8,0 226801776 4096 179.03

kworker/u16:0 20402 WM 8,0 285522744 4096 179.04

kworker/u16:0 20402 WM 8,0 289716352 4096 179.30

kworker/u16:0 20402 WM 8,0 289716480 4096 179.32

kworker/u16:0 20402 WM 8,0 289717120 4096 179.56

kworker/u16:0 20402 WM 8,0 289782040 4096 179.58

kworker/u16:0 20402 WM 8,0 302301320 4096 179.59

kworker/u16:0 20402 WM 8,0 306493488 4096 179.59

I have tried the same measurements on a older and cheaper SSD (with the same OS and applications) and did not see such latency peaks.

Am I missing something? What could be the cause of this?

Thank you!

[SDoni]

Hello Joe,

Any update on this one?

[Jose_H_Intel1]

What results do you get with no programs running, including the Windows* 7 VM?

[SDoni]

Hello Joe,

Same results even with no VM,

[Jose_H_Intel1]

Please allow us more time to investigate.

[SDoni]

Hi Joe,

Any news on this one?