Red Hat Bugzilla – Bug 116992
fastest checksum algorithm not chosen for RAID 5
Last modified: 2007-11-30 17:10:37 EST
Description of problem:
raid5: measuring checksumming speed
8regs : 2212.000 MB/sec
8regs_prefetch: 2020.000 MB/sec
32regs : 1488.000 MB/sec
32regs_prefetch: 1388.000 MB/sec
pIII_sse : 1600.000 MB/sec
pII_mmx : 3964.000 MB/sec
p5_mmx : 5272.000 MB/sec
raid5: using function: pIII_sse (1600.000 MB/sec)
Version-Release number of selected component (if applicable):
(probably all kernels between them too, didn't install those)
always on my system (haven't tried on others)
Steps to Reproduce:
1. Boot with an affected kernel on a system with a Linux software
RAID 5 volume (duh!)
says it's using the pIII_sse function
It should use the p5_mmx function, which is listed as fastest
Of course, I'm trusting the kernel isn't lying. Also, could be
other factors that are leading it to choose the slower function...
if so, would be nice if it would say so.
For all I know, this could have affected older (FC1, RH9, ...)
release kernels too... my logs don't go back far enough for me to
Created attachment 98095 [details]
This isn't a bug. It's intended to work this way.
It chooses the SSE routine over the others if it can use it, because
it avoids trashing whats in the cache.