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SubjectRe: Overscheduling DOES happen with high web server load.
Dean,
> As shipped, apache-1.3.6 on linux uses fcntl() file locking to prevent
> more than one process from being inside accept(). I'm not sure if the dec
> folks have rebuilt the server with -DSINGLE_LISTEN_UNSERIALIZED_ACCEPT...
> if they have, then there's no protection around accept() in servers
> listening on a single port.

Apache was built with the following flags:
(-DSINGLE_LIST_UNSERIALIZED_ACCEPT is not amoung them. )

./configure --prefix=/usr --libexecdir=/usr/lib/apache --sysconfdir=/etc/httpd/conf --datadir=/home/httpd --includedir=/usr/include/apache --logfiledir=/var/log/httpd --localstatedir=/var --runtimedir=/var/run --proxycachedir=/var/cache/httpd --enable-m
odule=all --enable-shared=max --disable-rule=WANTHSREGEX

Would it be better to build with -DSINGLE_LISTEN_UNSERIALIZED_ACCEPT? Is
this something that would help or hurt the "thundering herd" problem?

--Phil

Digital/Compaq: HPSD/Benchmark Performance Engineering
Phillip.Ezolt@compaq.com ezolt@perf.zko.dec.com


On Thu, 6 May 1999, Dean Gaudet wrote:

> As shipped, apache-1.3.6 on linux uses fcntl() file locking to prevent
> more than one process from being inside accept(). I'm not sure if the dec
> folks have rebuilt the server with -DSINGLE_LISTEN_UNSERIALIZED_ACCEPT...
> if they have, then there's no protection around accept() in servers
> listening on a single port.
>
> At any rate, for apache 1.3.x we require some form of locking (fcntl() in
> linux' case) when there are multiple listening sockets... so you also need
> to solve the thundering herd problem for fcntl() if it has one.
>
> Last time I brought up wake-on accept(), Alan said it is a hard problem.
> Maybe wake-one fcntl() is easier.
>
> Dean
>
>
>


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