collecting pv entries -- suggest increasing PMAP_SHPGPERPROC

[Chuck Swiger]

On Oct 27, 2008, at 11:39 AM, Francis Dubé wrote:
> I've read that this is mainly caused by Apache spawning too many  
> processes. Everyone seems to suggest to decrease the MaxClients  
> directive in Apache(set to 450 at the moment), but here's the  
> problem...i need to increase it ! During peaks all the processes are  
> in use, we even have little drops sometime because there isn't  
> enough processes to serve the requests. Our traffic is increasing  
> slowly over time so i'm affraid that it'll become a real problem  
> soon. Any tips on how I could deal with this situation, Apache's or  
> FreBSD's side ?

You need to keep your MaxClients setting limited to what your system  
can run under high load; generally the amount of system memory is the  
governing factor. [1]  If you set your MaxClients higher than that,  
your system will start swapping under the load and once you start  
hitting VM, it's game over: your throughput will plummet and clients  
will start getting lots of broken connections, just as you describe.

For a rough starting point, divide system RAM by httpd's typical  
resident memory size.  If your load legitimately exceeds this, you'll  
need to beef up the machine or run multiple webserver boxes behind a  
load-balancer (IPFW round-robin or similar with PF is a starting  
point, but something like a Netscaler or Foundry ServerIron are what  
the big websites generally use).

-- 
-Chuck

[1]: There can be other bottlenecks; sometimes poorly written external  
cgi-bin scripts or dynamic content coming from mod_perl, mod_php, etc  
can demand a lot of CPU or end up blocking on some resource (ie, DB  
locking) and choking the webserver performance before it runs out of  
RAM.  But you can run a site getting several million hits a day on a  
Sun E250 with only 1GB of RAM and 2 x ~400MHz CPU.  :-)