Re: [squid-users] Squid versus Microsoft ISA

On Fri, 5 Dec 2003, Henrik Nordstrom wrote:

> On Fri, 5 Dec 2003, Raphael Maseko wrote:
>
> > Have you been able to determine that Squid is actually making use of both
> > processors? Do you have other applications running on the same box?
>
> The main Squid process is a single process and can use at most one CPU.
> This is by design of Squid. Some CPU may be used by the diskd/aufs I/O
> slaves but not very much and it is doubtful this outweigths the general
> performance penalty of enabling SMP support in the kernel.

The only time that I've seen an SMP performance penalty is when you have
more than 5 or 6 processors. Up through 4 procesors there is a 1:1
performance improvement. This is what has been experienced with BSD/OS. A
few other operating systems that we've tried didn't fair as well.

There is, however, a 10 to 15 percent performance impact on Intel's current
Pentium4 and Xeon processors if you leave their hardware threading feature
enabled. Disable the feature in the BIOS and life improves.

While Squid, itself, will not benefit from multiple processors; the system
will. Most of the systems on which I have Squid running are located at the
organisation's security perimeter. The systems can be regarded as custom
firewalls as they are used to offload services that have high impact on the
performance of a general purpose firewall, e.g. DNS services, mail relaying,
and retrieval of web content.

At one site have two SMP systems. Each system has dual 550 MHz Pentium III
Xeon processors. Squid is running on each system and is only used to
retrieve Internet content for internal users. The systems are crudely load
balanced using a URL hashing algorithm. Since the systems were last booted
a year and a half ago, each system has been delivering between 2.5 and 4
terabytes of web content each month to internal clients. The average is
slightly over 3 terabytes. (This is a government facility with essentially
no activity outside of business hours (0700-1600) during the week and
absolutely no activity on holidays and weekends.)

The mail traffic is between 500 and 1000 messages per hour. I don't have
any good metrics on the average size of the messages. Unlike web activity,
this occurs 24 hours a day.

I think this might be an example of where SMP will be helpful.

Merton Campbell Crockett


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