i see 2 things here, classic queing problem, and the fact
that swapping to disk is 1000's of times slower than serving
from ram.
if you receive 100 requests per second but only have the
ram to serve 99, then swapping to disc occurs which slows
down the entire system. the next second comes and 100 new
requests come in, plus the 1 you had in the queue that did not
get serviced in the previous second. after a little while,
your memory requirements start to soar, lots of swapping is
occuring, and requests are coming in at a higher rate than can
be serviced by an ever slowing machine. this leads to a rapid
downward spiral. you must have enough ram to service all the apache
processes that are allowed to run at one time. its been my experience
that once swapping starts to occur, the whole thing is going to spiral
downward very quickly. you either need to add more ram, to service
that amount of apache processes that need to be running simultaneously,
or you need to reduce MaxClients and let apache turn away requests.
--
___cliff [EMAIL PROTECTED]http://www.genwax.com/
P.S. used your service several times with good results! (and no waiting) thanks!
Justin wrote:
> I need more horsepower. Yes I'd agree with that !
>
> However... which web solution would you prefer:
>
> A. (ideal)
> load equals horsepower:
> all requests serviced in <=250ms
> load slightly more than horsepower:
> linear falloff in response time, as a function of % overload
>
> ..or..
>
> B. (modperl+front end)
> load equals horsepower:
> all requests serviced in <=250ms
> sustained load *slightly* more than horsepower
> site too slow to be usable by anyone, few seeing pages
>
> Don't all benchmarks (of disk, webservers, and so on),
> always continue increasing load well past optimal levels,
> to check there are no nasty surprises out there.. ?
>
> regards
> -justin
>
> On Thu, Jan 04, 2001 at 11:10:25AM -0500, Vivek Khera wrote:
> > >>>>> "J" == Justin <[EMAIL PROTECTED]> writes:
> >
> > J> When things get slow on the back end, the front end can fill with
> > J> 120 *requests* .. all queued for the 20 available modperl slots..
> > J> hence long queues for service, results in nobody getting anything,
> >
> > You simply don't have enough horsepower to serve your load, then.
> >
> > Your options are: get more RAM, get faster CPU, make your application
> > smaller by sharing more code (pretty much whatever else is in the
> > tuning docs), or split your load across multiple machines.
> >
> > If your front ends are doing nothing but buffering the pages for the
> > mod_perl backends, then you probably need to lower the ratio of
> > frontends to back ends from your 6 to 1 to something like 3 to 1.
> >
> > --
> > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> > Vivek Khera, Ph.D. Khera Communications, Inc.
> > Internet: [EMAIL PROTECTED] Rockville, MD +1-240-453-8497
> > AIM: vivekkhera Y!: vivek_khera http://www.khera.org/~vivek/
>
> --
> Justin Beech http://www.dslreports.com
> Phone:212-269-7052 x252 FAX inbox: 212-937-3800
> mailto:[EMAIL PROTECTED] --- http://dslreports.com/contacts
