RAID-0 read perf. decrease after 2.4.20
On Monday 08 December 2003 13:47, Marcelo Tosatti wrote:
Hi Marcelo,
Quoted 2 lines
2.4.20-aa included rmap and some VM modifications most notably "
drop_behind()" logic which I believe should be the reason for the
huge
Quoted 1 line
read speedups. Can you please try it? Against 2.4.23.
Just some feedback:
echo 511 > /proc/sys/vm/max-readahead
brings back the read performance of my 30 disks on 4 controller
LVM/RAID0.
Cheers
Martin
=====
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de www: http://www.knobisoft.de
Quoted 7 lines · Martin Knoblauch
On Monday 08 December 2003 13:47, Marcelo Tosatti wrote:
Hi Marcelo,
Quoted 2 lines
2.4.20-aa included rmap and some VM modifications most notably "
drop_behind()" logic which I believe should be the reason for thehuge
Quoted 8 lines
Quoted 1 line
read speedups. Can you please try it? Against 2.4.23.
Just some feedback:
echo 511 >
/proc/sys/vm/max-readaheadbrings back the read performance of my 30 disks on 4 controller
LVM/RAID0.
Great.
Quoted 14 lines · --- Marcelo Tosatti
Quoted 6 lines · Martin Knoblauch
On Monday 08 December 2003 13:47, Marcelo Tosatti wrote:
Hi Marcelo,
Quoted 2 lines
2.4.20-aa included rmap and some VM modifications most notably "
drop_behind()" logic which I believe should be the reason forthe
Quoted 3 lines
huge
Quoted 1 line
read speedups. Can you please try it? Against 2.4.23.
Quoted 9 lines
Quoted 6 lines
Just some feedback:
echo 511 >
/proc/sys/vm/max-readaheadbrings back the read performance of my 30 disks on 4 controller
LVM/RAID0.Great.
Indeed :-) Just to clarify - the modification of max-readahead was
sufficient to "fix" the observed read performance degradation. I did not apply (or reverse) anything on top of 2.4.22.
Actually 255 would have been sufficient, 511 proved to be a small bit
better :-))
Martin
=====
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de www: http://www.knobisoft.de
Hello again!
Finally had time to test this on IDE, "better late than even later"...
Quoted 10 lines · Martin Knoblauch
Quoted 9 lines
Quoted 6 lines
Just some feedback:
echo 511 >
/proc/sys/vm/max-readaheadbrings back the read performance of my 30 disks on 4 controller
LVM/RAID0.Great.
Quoted 6 lines
Indeed :-) Just to clarify - the modification of max-readahead was
sufficient to "fix" the observed read performance degradation. I did not apply (or reverse) anything on top of 2.4.22.Actually 255 would have been sufficient, 511 proved to be a small bit
better :-))
The "max-readahead" does not seem to affect IDE-RAID, at least not with the 2.4.27-pre6 I just compiled on two machines. So the problem still exists, read speed on 2.4.20-ac2 is almost twice as fast as on later kernels :-/
Have a nice summer,
Mikael J.
http://www.helsinki.fi/~mpjohans/
Quoted 9 lines · Marcelo Tosatti
Quoted 6 lines · Martin Knoblauch
Just some feedback:
echo 511 >
/proc/sys/vm/max-readaheadbrings back the read performance of my 30 disks on 4 controller
LVM/RAID0.Great.
Maybe a new default is in order?
Quoted 4 lines · Mike Fedyk
Quoted 3 lines · Marcelo Tosatti
Quoted 2 lines · Martin Knoblauch
Just some feedback:
Quoted 8 lines
Quoted 6 lines
Quoted 4 lines
echo 511 >
/proc/sys/vm/max-readaheadbrings back the read performance of my 30 disks on 4 controller
LVM/RAID0.Great.
Maybe a new default is in order?
I believe the defaults have been changed because they harm smaller workloads.