Re: wrong in_flight diskstat in

From: Martin Devera
Date: Tue May 23 2006 - 05:30:37 EST

Jens Axboe wrote:
On Tue, May 23 2006, Martin Devera wrote:

I see weird output from /sys/block/sd{a,b}/stat on our AMD64-X2 smp machine with HT1000 (Broadcom) SATA with 2 WD 250GB HDDs in MD raid1. AS scheduler was used, change to noop didn't change anything. It is vanilla and here are absolute values in hex and one second differences below:

132CDF 56D62 61753C0 6966BC 165A8EB 5FF5B6C 3B32D6C0 1110594C FFCA89A4 FEE85878 49FF74E4
132CDF 56D62 61753C0 6966BC 165A8EF 5FF5B6C 3B32D6E0 111059D0 FFCA89A1 FEE85C60 79291244
0: 0
1: 0
2: 0
3: 0
4: 4
5: 0
6: 32
7: 132
8: -3
9: 1000
10: 791256416

As you can see in_flight is constantly negative and it is DECREASING slowly all the time.
I can't find any reason for it :-\

Are you using io barriers?

[PATCH] blk: fix gendisk->in_flight accounting during barrier sequence

I don't think so, I just used
mount / -o remount,barrier=0
to make it sure and it keeps decrementing. I'll however apply the patch (and others up to at night (I'm not allowed to restart the machine just now).
thanks, Martin
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