Re: It's about aic79xx on FreeBSD 4.11 SMP kernel, reduce disk speed rate.

[Chuck Swiger]

[ This question is far off-topic for bug-gnu-utils, Followup-To: set to 
<address@hidden>, which is much more appropriate list... ]

Takuya tseng wrote:
> Did anyone ever met after compile Adaptec U320 SCSI driver on FreeBSD 
> 4.11SMP mode that will occur SCSI disk reduce speed rate? Before we post
> this mail, we try to download aix79xx source code from Adaptec to replace
> it. But after our check that source code version seems not new than FreeBSD 
> 4.11built-in. Did anyone ever meet this circumstance?

FreeBSD 4.x uses a single Giant kernel lock when operating in SMP mode, which 
does cause additional locking overhead in the drivers and reduces the maximum 
concurrency compared to the fine-grained locking found in 5.x or later versions 
FreeBSD.  This should not affect the actual SCSI bus tranfer rates, or that of 
attached devices, but I suppose it might cause slightly slower observed disk 
performance compared to a single-processor kernel.

I would not expect this decrease to be significant, but you might want to try 
either FreeBSD 5.4 or the FreeBSD-6 betas instead.

--
-Chuck