回复:Re: What to know detail about why Squid use single process.

Thanks, Joe pal!

I have two questions, what means "poll or /dev/poll and/or kqueues"
in your reply?

Another question, I do not understand the following that you mentioned,

/////////////////////////////////////////////////////////////////
Though it is likely
that part of the scalability problem with Oops is its reliance on the
BerkelyDB (or GigaBase) for it's storage backend.
/////////////////////////////////////////////////////////////////

Can you give me a simple explanation. :-)

Best regards,
George Ma

----- 原文 -----
From: Joe Cooper
To: maer727@sohu.com
Cc: squid-dev@squid-cache.org
Subject: Re: What to know detail about why Squid use single process.
Sent: Tue Apr 23 22:58:59 CST 2002

> Even though others have jumped in on this, I'll point out some
> documentation:
>
> The C10K Problem page operated by Dan Kegel has load of information on
> all major concurrency models in use today, including the still preferred
> state machine style model that is similar to what Squid uses:
>
> http://www.kegel.com/c10k.html
>
> It is pretty much a given that threads are a rather heavy way to achieve
> concurrency, and though they are easier to program in languages that
> have mechanisms to make it easier (Java, C++, being the primary choices
> in the context of near-system level projects like Squid), they can be
> very bug-prone in C. Then again, that's not to say one couldn't design
> a highly concurrent application like Squid with threads, but it is worth
> noting that the most popular open source competition for Squid (Oops)
> uses a threaded model and does not scale up to higher client loads as
> well as Squid even though it is a newer design. Though it is likely
> that part of the scalability problem with Oops is its reliance on the
> BerkelyDB (or GigaBase) for it's storage backend.
>
> Kotetu also uses a threaded design I believe, and it /does/ manage to
> scale slightly better than Squid if given enough disks, but I'm not
> familiar enough with it to know for sure what kind of architecture they
> have.
>
> Anyway, I suspect that if the current Squid developers were to start
> over from scratch today they would again choose a state machine model
> based around poll or /dev/poll and/or kqueues. It is still the fastest
> model available to us.
>
> maer727@sohu.com wrote:
> > Hi, pals!
> >
> > I read from Programming Guide that Squid is a single process
> > application. I also learn the shortcoming of multi-process
> > (multi-thread). Here is what the Programming Guide says,
> >
> > //////////////////////////////////////////////////////////////////////
> > Squid does not use a ``threads package'' such has Pthreads. While
> > this might be easier to code, it suffers from portability and
> > performance problems. Instead Squid maintains data structures and
> > state information for each active request.
> > //////////////////////////////////////////////////////////////////////
> >
> > I am very interested in the field and want to know details about what
> > is the shortcoming of multi-process/thread. Why Squid choose single
> > process? Are there any detailed documents?
> >
> > Best regards,
> > George Ma
> >
> >
>
>
>
> --
> Joe Cooper <joe@swelltech.com>
> http://www.swelltech.com
> Web Caching Appliances and Support
>
Received on Tue Apr 23 2002 - 23:06:24 MDT