[Stgt-devel] ibmvio is slow

[Bastian Blank]

Hi folks

I tried the ibmvio target on a busy vioserver on a power5 machine. It
works fine, I got no problem. It provides services to 7 initiators with
at least 2 luns each.

But it is slow. I can write at most 15MiB/s to the disks, regardless of
the count of the initiators and disks.

I used strace and saw the following:

| mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_SHARED, 14, 0xc6185) = 0xf7e28000 <0.000026>
| write(8, "\0", 1)                       = 1 <0.002088>
| munmap(0xf7f5e000, 12288)               = 0 <0.000022>
| mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_SHARED, 14, 0xc61a5) = 0xf7e08000 <0.000025>
| write(8, "\0", 1)                       = 1 <0.002060>
| munmap(0xf7fde000, 4096)                = 0 <0.000022>
| mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_SHARED, 14, 0xc61c5) = 0xf7de8000 <0.000023>
| write(8, "\0", 1)                       = 1 <0.002130>
| munmap(0xf7f12000, 73728)               = 0 <0.000031>

Each request produces a mmap, a write and a unmap. The time needed for the
write, which seems to be a request available flag, needs 2ms, which means at
most 50 requests/s.

Bastian

-- 
Bones: "The man's DEAD, Jim!"