Re: Help!!

On Wed, 5 Jul 2000, David Luyer wrote:

> > On Mon, 3 Jul 2000, jubaco30 wrote:
> > > I need to know urgently(An Administrative Decision) if squid takes
> > > advantage of SMP (Redhat 6.2 with 2 processors). The main questions is
> > > if the granularity of locks in I/O lead to similar performance(with
> > > smp, without smp)?.
> >
> > It is my understanding that Squid is implemented as a single process with
> > its own internal state machine/executive to manage its activity.
>
> Under Linux it multi-threads if you enable ASYNCIO, which means it scales
> much better over multiple separate disks (without RAID).
>
> > Under BSD/OS 4.x, Squid's apparent performce improved dramatically on
> > multi-processor systems. The observed performance improvement on the dual-
> > and quad-processor systems that we have is more a function of how well the
> > OS manages its resources and activities in an SMP environment.
>
> Under BSD/OS you're likely to not be using ASYNCIO, so you have limited
> gain from SMP for Squid, but there is still some gain there.
>
> > While we do have a few Linux systems, we tend to use BSD/OS where the
> > leather meets the road. This is probably more a function of two decades of
> > experience with the Berkeley Software Distribution from CSRG and BSDi.
>
> Well we use it too (as a result of policy, not of choice) but the number
> of bugs and lack of development tools is just damn annoying to people
> who are used to something as robust and well supported for development as
> Linux. Fortunately Squid doesn't hit many of the bugs (but OTOH it doesn't
> do ASYNCIO under BSD/OS which is a bit of a performance pain, but can be
> countered by just buying faster boxes than you would need to with Linux).

I gather from your comments that ASYNCIO is similar in nature to the BSD/OS
file system's "soft update" feature. As I recall from a colleague's tests,
the performance improvement from using "soft updates" eliminated the need
to add a second processor to systems we were designing for our customers.

Interestingly BSDi doesn't tout this feature all that much. I guess it
doesn't have the sex-appeal of the SMP cachet.

Merton Campbell Crockett
Received on Wed Jul 05 2000 - 07:54:48 MDT