shared mem and panics when out of PV Entries

[Igor Sysoev]

On Wed, 26 Mar 2003, Andrew Kinney wrote:

> Eventually, I may be forced to turn off KeepAlive and make use of 

If you disable keepalive I believe clients would not see much difference.
Keepalive is a good feature for clients but it should be enabled
if you have enough resources to support it.

It can be enabled on light-weight server that uses kqueue and designed
to handle the tens of thousands simultaneous connections.  An overhead
per connection would be several tens of kilobytes or less.
A plain Apache without heavy modules spends hunderds of kilobytes of
physical memory per connection. mod_perl spends megabytes or tens of
megabytes of phycical memory per connection.  In your untypical case
Apache spends about 1.5M per connection of a kernel memory.

> FreeBSD's accept filters

My measurements on the loaded enough web sites show that the accept filters
allow to save about 5-10% of Apaches. Of course they are the most effective
without keepalives.

But be sure use them only in between 4.1.1-RELEASE - 4.4-RELEASE, or
4.6-RELEASE and above.  4.5-RELEASE and -STABLE around have the syncache
related bug that leads to DoS.

> or put in a reverse proxy as you recommend.

I can even recommend you one proxy - mod_accel - http://sysoev.ru/en/

> For now, though, we are serving the whole gammut 
> from this Apache.  Static pages, images, mod_perl, PHP, 
> Apache::ASP, and most anything else a customer might want or 
> need to serve from a web server.  I know it isn't the most efficient 
> way to use Apache, but nobody has any complaints about 
> performance at this point.

You have too much overhead per connection and if the worload would grow
you will have perfomance problems.


Igor Sysoev
http://sysoev.ru/en/