Hi, When your server is slow: - how is your iowait ? maybe apache is waiting for disk access. - are your sure that you don't have a network bottleneck ? load balancer, firewall, network interface,.. - do you serve static files only with you apache ? if you use php, cgi,mod_jk,mysql,... You should have a look to them maybe they are hanging up. - if you use thread safe modules (not php) and if you have to serve a lot of little requests, maybe you can consider to use mpm worker instead of prefork.
-- Bj On 10/1/07, Alec Matusis <[EMAIL PROTECTED]> wrote: > > Hi Christian, > > > How does your apache look memory-wise in top/htop? > > When Apache is "slow", it has about 200 processes with 11-15MB RSS each, > soat least 1GB of physical RAM should be unused. > The load average drops from normal 16.0 (this is a 4 CPU machine) to only > 6.0 when apache becomes "slow". > > > It would be interesting to see an example of a reasonable choice for > MaxMemFree, after 2 days of searching in Google I cannot find any guidelines > for setting it. > > > > > -----Original Message----- > > From: Christian Folini [mailto:[EMAIL PROTECTED] > > Sent: Sunday, September 30, 2007 11:55 PM > > To: users@httpd.apache.org > > Subject: Re: [EMAIL PROTECTED] requests time-out under load, no warnings in > > logs > > > > Hey Alec, > > > > This looks like a tricky problem. Have you looked at the traffic > > using tcpdump or ethereal when the machine hangs? You might > > also try out mod_forensic or mod_security and add mod_security > > internal timestamps to the access-log. Using these logs you will > > get a clearer idea where it hangs. > > > > How does your apache look memory-wise in top/htop? > > Are you sure it is not an application issue - even if it shows > > serving static files. A reverse proxy setup for testing purposes > > could seperate application and static file serving to > > give you a clearer idea in this regard. > > > > These are just a lot of ideas. I do not really know how to > > solve your problem, but this would give you a clearer idea > > of the problem. > > > > I am not familiar with best practice values for MaxMemFree. > > > > regs, > > > > Christian > > > > > > > > On Sun, Sep 30, 2007 at 03:54:59PM -0700, Alec Matusis wrote: > > > We are running a busy Apache/2.0.54 server on 2.6.9 kernel, that > > suddenly > > > becomes very slow- requests either time out, or it takes 10s to serve > > a 1K > > > thumbnail. > > > It is usually correlated with load spikes, but not perfectly (by > > looking at > > > the bandwidth graph) > > > Then it requires a stop/start, and it becomes fast again. > > > This has been happening before, and it was always accompanied with > > > > > > [error] server reached MaxClients setting, consider raising the > > MaxClients > > > setting > > > > > > in the apache log. > > > > > > We raised MaxClients from 200 to 300, and now it happens with no > > warning > > > in any logs at all, except with the usual > > > > > > web10 kernel: possible SYN flooding on port 80. Sending cookies. in > > > /var/log/messages (this has always happened when apache hung from > > overload). > > > > > > What worries me is that there are no log messages in apache logs at > > all when > > > this happens. > > > > > > This is the relevant part of httpd.conf > > > > > > ServerLimit 300 > > > # we are using prefork MPM > > > <IfModule prefork.c> > > > StartServers 10 > > > MinSpareServers 5 > > > MaxSpareServers 20 > > > MaxClients 300 > > > MaxRequestsPerChild 10000 > > > MaxMemFree 2560 > > > </IfModule> > > > > > > The server has 4GB of RAM and 4GB of swap. When apache "crashes" i.e. > > > becomes very slow, the swap size is still 0 and vmstat shows no > > swapping. > > > I suspect the problem may be in > > > > > > MaxMemFree 2560 > > > > > > but then I would expect some kind of "out of memory" errors in the > > logs? > > > Another question: what is the good choice of MaxMemFree value? We > > want to > > > leave 512MB-1GB or RAM on this machine for other tasks. > > > > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > > The official User-To-User support forum of the Apache HTTP Server > > Project. > > > See <URL:http://httpd.apache.org/userslist.html> for more info. > > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > > " from the digest: [EMAIL PROTECTED] > > > For additional commands, e-mail: [EMAIL PROTECTED] > > > > > > > --------------------------------------------------------------------- > > The official User-To-User support forum of the Apache HTTP Server > > Project. > > See <URL:http://httpd.apache.org/userslist.html> for more info. > > To unsubscribe, e-mail: [EMAIL PROTECTED] > > " from the digest: [EMAIL PROTECTED] > > For additional commands, e-mail: [EMAIL PROTECTED] > > > --------------------------------------------------------------------- > The official User-To-User support forum of the Apache HTTP Server Project. > See <URL:http://httpd.apache.org/userslist.html> for more info. > To unsubscribe, e-mail: [EMAIL PROTECTED] > " from the digest: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > >
