Messages in this thread | | | Subject | Re: Fwd: Re: Performance figure for sx8 driver | From | Kallol Biswas <> | Date | 12 Jun 2005 10:43:17 -0700 |
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I have been investigating what the cause of performance loss could be.
I have noticed several things:
0) Setting to CARM_MAX_Q to 30 hangs. So we have been testing only with CARM_MAX_Q == 1. The firmware has not been updated yet.
1) If we keep on increasing number of SATA disks, hdparm does not get multiplied total read performance (hdparm -t ....).
With a Maxtor 60 GB disk with 8MB cache we get 50Mb/sec. If we put two disks we get 35 on each. Total 70MB/sec. If we put more then total does not get above 70MB/sec.
It looks like that a part of the driver serializes the commands. We have a 32 processor MIPS based system.
2) It looks like that there is while(1) loop under spinlock in isr stack. If we start queuing many commands then it may take a while for this loop to break. Though I am not quite familiar with the driver yet.
If we set CARM_MAX_Q to 30 then the request/response queue length should also be increased right?
3) Next I will put PCI-X analyzer and figure out the root cause of performance loss. May be need to get hold of the technical manual.
Kallol
On Sun, 2005-06-12 at 09:30, Mark Lord wrote: > kallol@nucleodyne.com wrote: > > > > > > Hello Jeff, > > How did you verify that performance improved making the > > changes those > > you suggested? > > > > hdparm does not show it. > > My hdparm tool performs a single I/O at a time, > disregarding any kernel read-ahead that may be added on. > > As such, it won't often show the effects of queued commands > as well as some other test might. > > Cheers > - > To unsubscribe from this list: send the line "unsubscribe linux-ide" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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