On 2/9/07, hkclark@xxxxxxxxx <hkclark@xxxxxxxxx> wrote:
On 2/9/07, Vasiliy Boulytchev <vasiliy@xxxxxxxxxxxxxxxx> wrote: > Gents, am I reading this information incorrectly, or is this box also > swapping about 128M? Swapping will quickly grind your system to a halt. > > I guess this all depends on how many people are connecting to your > apache servers... Turn on your server-info and see :) > > Vasiliy Boulytchev > vasiliy@xxxxxxxxxxxxxxxx > Hmmm, now that you mention it, that's a very good point. Does anyone out there know why CentOS 3 would swap out so much vs. "giving back real RAM" from buffers and/or cache? I agree with Vasiliy that it looks like the performance on this box could be pretty lame if anything important is in that swap (I would assume the OS is putting the "oldest" stuff in swap, but what if an app didn't need to get used very often and it suddenly received a request... that request could easily time out while stuff is swapping back in from disk, right?). Does anyone know a good way to see which app(s) and/or parts of the OS/libs are being put into swap vs. kept in "real RAM"? Regards, KC
PS -- To partially reply to my own post, a few moments after I hit send (doh! doesn't that always happen!), I remembered reading a while back some info on the "swappiness" setting in 2.6 kernels. I know I saved some links to the stuff I was reading, but of course I can't find those links now to save my life! :-( Here is one of them (there are also threads re swappiness in the archives for this list): http://kerneltrap.org/node/3000 But, if I'm not mistaken, this is all a 2.6 kernel (CentOS 4) thing, so you can't adjust it in CentOS 3. Therefore, I guess one answer to my question is "2.4 kernels have some baked in swappiness value that you can't adjust, so it is what it is"... however, if anyone has other insights on how to maximize performance and swap vs. real mem on CentOS 3 boxes, I'm all ears. Thanks, KC _______________________________________________ CentOS mailing list CentOS@xxxxxxxxxx http://lists.centos.org/mailman/listinfo/centos
