Messages in this thread | | | Date | Wed, 3 Mar 1999 07:06:16 -0800 | From | (Jim Gettys) | Subject | Re: OSDI paper - IO-Lite: A Unified I/O Buffering and Caching System |
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> From: Oliver Xymoron <oxymoron@waste.org> > Date: Tue, 2 Mar 1999 23:41:28 -0600 (CST) > To: Jim Gettys <jg@pa.dec.com> > Cc: linux-kernel <linux-kernel@vger.rutgers.edu> > Subject: Re: OSDI paper - IO-Lite: A Unified I/O Buffering and Caching System > ----- > On Tue, 2 Mar 1999, Jim Gettys wrote: > > > It shows a new I/O approach that is very general and flexible, and avoids > > data copies with minimal overhead, even between processes. The authors > > use as an example Web service, and show very good performance gains. > > Very interesting. We probably wouldn't see quite the gains the author saw > with his FreeBSD implementation. It's a good match for FreeBSD as it > already has a zero-copy scheme in a lot of areas and fits better with > their design philosophy. Linux largely avoids VM manipulations like those > suggested for instance by I/O-Lite's IPC scheme, because of their nasty > effect on CPU caches, SMP scaling, etc. So parts of it are going to be a > hard sell. And we've got sendfile(2) now, which is not nearly as pretty or > generic, but might still give similar performance at least for the common > web server case. > >
Sendfile does not help the CGI case, which is very common (or dominant) on many (most) high volume servers.
I believe it will also help the CPU cache case for CGI; it avoids having to touch the data again in many operations, which would pollute the cache with data that was merely copied in the web server. - Jim
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