[ kvm-Bugs-2723366 ] ltp diotest running time is 2.54 times than before

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Bugs item #2723366, was opened at 2009-03-31 07:00
Message generated for change (Comment added) made by jiajun
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=893831&aid=2723366&group_id=180599

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Category: qemu
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Jiajun Xu (jiajun)
Assigned to: Nobody/Anonymous (nobody)
Summary: ltp diotest running time is 2.54 times than before

Initial Comment:
Running LTP diotest in guest costs about 2m22s in latest commit which it needs 0m56s in older commit.

New kvm kernel commit:a317a1e496b22d1520218ecf16a02498b99645e2 
kvm user-space commit: df0e52a8d988d55dd42f8d46faffa9faa41892c9
ltp diotest running time: 5 rounds of diotest average time: 2m22s

Old kvm kernel commit:e74bb3fa8e55284dc6fdd68aa9da833ce07a4295
kvm user-space commit: 4c1083fd610fba4eedb45553c0a579b7b6593f1a
ltp diotest running time: 5 rounds of diotest average time: 0m56s

Reproduce steps:
(1)qemu-system-x86_64  -m 512 -smp 4  -net nic,macaddr=00:16:3e:12:0d:3c,model=rtl8139 -net tap,script=/etc/kvm/qemu-ifup -hda /share/xvs/var/ia32e_rhel4u1.img
(2)Get LTP package from sourceforge and install it in guest
(3)Run diotest for 5 times.
while [ $i -lt 5 ]
do
    time /ltp-full-20070930/runltp -l /tmp/ltp_dio.log -f dio -p -q >>
/root/ltp.log
    ((i++))
done

Notes:
The data is running with ltp-full-20070930, and we also tried latest ltp package ltp-full-20090228, which can get similar data.


----------------------------------------------------------------------

>Comment By: Jiajun Xu (jiajun)
Date: 2009-10-18 22:55

Message:
I checked with kvm: f3ed8d80..., qemu-kvm: 3c62010..., is still takes more
than 2 minutes to finish diotest with "cache=writethrough".

----------------------------------------------------------------------

Comment By: Marcelo Tosatti (mtosatti)
Date: 2009-10-17 18:10

Message:
Jiajun,

This was probably caused by the default caching mode change to writeback.

Can you verify if "cache=writethrough" option takes performance back to
0m56s range 
as before?


----------------------------------------------------------------------

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