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:christian.folini@xxxxxxx] > Sent: Sunday, September 30, 2007 11:55 PM > To: users@xxxxxxxxxxxxxxxx > Subject: Re: 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: users-unsubscribe@xxxxxxxxxxxxxxxx > > " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx > > For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx > > > > --------------------------------------------------------------------- > 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: users-unsubscribe@xxxxxxxxxxxxxxxx > " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx > For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx --------------------------------------------------------------------- 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: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
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