lkml.org 
[lkml]   [2012]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Why blktrace didn't trace requests merge?
On 2012-09-17 19:55, Tejun Heo wrote:
> (cc'ing Jens)
>
> On Mon, Sep 17, 2012 at 09:22:28AM -0400, Steven Rostedt wrote:
>> On Mon, 2012-09-17 at 19:33 +0800, Jianpeng Ma wrote:
>>> Hi all:
>>> I used blktrace to trace some io.But i can't find requests merge. I searched the code and did't not find.
>>> Why?
>>>
>>
>> No idea. I don't use blktrace much, but I Cc'd those that understand it
>> better than I.

Works for me:

[...]


8,0 0 26 0.009147735 664 A WS 315226143 + 8 <- (8,7) 19406344
8,0 0 27 0.009148677 664 Q WS 315226143 + 8 [btrfs-submit-1]
8,0 0 28 0.009152967 664 G WS 315226143 + 8 [btrfs-submit-1]
8,0 0 29 0.009154242 664 P N [btrfs-submit-1]
8,0 0 30 0.009155538 664 A WS 315226151 + 8 <- (8,7) 19406352
8,0 0 31 0.009155743 664 Q WS 315226151 + 8 [btrfs-submit-1]
8,0 0 32 0.009157086 664 M WS 315226151 + 8 [btrfs-submit-1]
8,0 0 33 0.009158716 664 I WS 315226143 + 16 [btrfs-submit-1]

That's from a quick trace of /dev/sda. I started blktrace, then did:

$ dd if=/dev/zero of=foo bs=4k count=128 && sync

to ensure that I knew merges would be happening. Output stats at the end:

Total (sda):
Reads Queued: 7, 44KiB Writes Queued: 447, 7692KiB
Read Dispatches: 7, 44KiB Write Dispatches: 416, 7692KiB
Reads Requeued: 0 Writes Requeued: 0
Reads Completed: 7, 44KiB Writes Completed: 435, 5864KiB
Read Merges: 0, 0KiB Write Merges: 23, 428KiB
IO unplugs: 78 Timer unplugs: 0

--
Jens Axboe



\
 
 \ /
  Last update: 2012-09-17 21:01    [W:0.105 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site