I noticed one of our CentOS machines was very close to 100% memory usage last night. The load average on the machine shot up to ~16 and I noticed that there were several pdflush processes that were blocked on Disk IO (run state D in top). I thought pdflush was used to swap data from memory to disk (os memory paging), but that particular server didn't have a swap partition mounted. So what was pdflush actually doing in this case?
For the health of your system, please set up a swap partition for your server (or
Unix-like systems expect to be able to swap. Bad Things can happen when there is no available swap (like the disk buffer cache getting squeezed down to a tiny bit of memory, which can really make