* Matthew Dillon <[EMAIL PROTECTED]> [000110 16:04] wrote:
> :Recently I was tasked to find a way to scale up our MYSQL server, running
> :MYSQL3.22.15 on FreeBSD3.3. I've been testing a hardware RAID solution,
> :and found that with 6 disks in a RAID5 configuration, the system was only
> :perhaps 30% faster than when running on a single disk. [The 6 disks in the
> :RAID5 are the same model as the single-disk test I was comparing against.]
> :
> :Experimentation determined that pthreads was the problem. FreeBSD's
> :implementation of pthreads using a select() loop, and select() always says
> :that disk I/O is ready to proceed, and disk I/O never return EWOULDBLOCK.
> :Essentially, pthreads was serializing the MYSQL read() requests, and if the
> :dataset exceeds memory size, performance becomes entirely seek bound.
> :
> :I've implemented a rough fix, which is to rfork() processes which I label
> :...
> :Thanks,
> :scott
>
> A better solution may be to shift to FreeBSD4.0 (when it's released -
> wait for it to become good and stable), and then use the native
> linuxthreads port (/usr/ports/devel/linuxthreads) for FreeBSD.
>
> The linuxthreads port is at least four times faster and, since it uses
> rfork(), will be I/O optimal. However, since only FreeBSD-4.x implements
> rfork(...RF_MEM) you can only use it with FreeBSD-4.x (or am I wrong
> there?).
I'm pretty sure RF_MEM doesn't work in 3.x with SMP, under UP it should
work fine.
-Alfred
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