>> I ran into an out of memory problem. The first mention of it in the >> kernel log is "mysqld invoked oom-killer". I haven't run into this >> before. I do have a swap partition but I don't activate it based >> on something I read previously that I later found out was wrong so >> I suppose I should activate it. Is fstab the way to do that? I >> have a commented line in there for swap. >> >> Can anyone tell how much swap this is: >> >> /dev/sda2 80325 1140614 530145 82 Linux swap / >> Solaris >> >> If it's something like 512MB, that may not have prevented me from >> running out of memory since I have 4GB RAM. Is there any way to >> find out if there was a memory leak or other problem that should be >> investigated? > > To activate swap, put a line in fstab like so: > > /dev/sda2 none swap sw 0 0 > > However, you do not want to use it. it is not the life-saver some > howto authors on the internet claim it to be. > > When a linux machine hits swap, it does so very aggressively, there is > nothing nice about it at all. The entire machine slows to a > painstaking crawl for easily a minute at a time while the kernel > writes pages out to disk, and disk is thousands of times slower than > RAM. > > It gets so bad that you can't even run a shell properly to try and see > what's going on and kill the actual memory hog. > > My personal rule of thumb: if you hit swap, the bad thing has already > gone very very south, usually to the point where you can't do much > about it and it's already too late. Besides, that bastard deomon spawn > of satan called the oom-killer is likely about to kick in and REALLY > make your day. Anyone else notice how oom-killer seems to be hard > coded to zap the most inconvenient process of all?..... > > What you need to be doing is monitor your memory usage during normal > conditions and deal with issues before they become problems.
Hi Alan, I think it was your advice I took a long time ago when I stopped installing new machines with a swap partition and disabled it on my already-installed machines. Some time later, others on this list caught wind of what I'd done and told me I was an idiot. Is there a consensus on this? If the drawbacks and advantages of using swap cancel each other out, I won't use it. - Grant
