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

[Takuya tseng]

Hi Chuck,
Thanks a lot for your help. I'll try FreeBSD 5.4 version. BTW, do you know 
where is single Giant kernel lock ? Cause that I'm a newbie about hacking 
FreeBSD kernel. So could you please advise me it ?
 Thanks,
 Takuya Tseng

 On 9/16/05, Chuck Swiger <address@hidden> wrote: 
> 
> [ 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
>