[Stgt-devel] ibmvio is slow

[Ming Zhang]

On Tue, 2007-08-14 at 20:36 +0200, Bastian Blank wrote:
> On Tue, Jun 19, 2007 at 07:18:38PM +0200, Bastian Blank wrote:
> > But it is slow. I can write at most 15MiB/s to the disks, regardless of
> > the count of the initiators and disks.
> 
> I did another round of tests with 2.6.22 and a corresponsing patchset
> and an uptodate tgtd with disabled controller lun (it breaks my setup
> which needs the boot disk on lun 0).
> 
> Writing on an exported device shows weird behaviour. iostat shows many
> write _and_ read requests, even if the initiator only emits write
> requests:

what kind of write io u did? make a fs and run bonnie?

try simple dd on a raw device (no fs) and see the performance. if write
result is much better and u do not see read in iostat, u meet an align
issue simply like what we had in IET list.


> 
> | Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
> | sdb            3733.90  4177.60 525.80 72.70 34138.40 34002.40   113.85    19.94   33.32   1.38  82.76
> 
> If the initiator emits read requests, it is okay:
> 
> | Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
> | sdb           13798.50     0.40 1955.31  0.20 126057.72     4.81    64.47     1.18    0.60   0.43  83.21
> 
> There is only lvm between it. This looks like some sort of read-ahead
> for the data, which should not happen for write requests. I tried to dig
> a little bit in the block code but was not able to found the cause.
> 
> Bonnie shows the following:
> | Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
> |                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> | Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> | test.track.rz.un 2G           21914  10 15207   4           59795   6 305.8   0
> 
> Bastian
> 
-- 
Ming Zhang


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