On Thu, Jun 10, 2010 at 04:00:54PM -0400, Greg Smith wrote: >> 5. Does anybody know if I can set dirty_background_ratio to 0.5? As we >> have 12 GB RAM and rather slow disks 0,5% would result in a maximum of >> 61MB dirty pages. > > Nope. Linux has absolutely terrible controls for this critical > performance parameter. The sort of multi-second spikes you're seeing > are extremely common and very difficult to get rid of. Another relevent parameter is /proc/sys/vm/dirty_writeback_centisecs. By default linux only wakes up once every 5 seconds to check if there is stuff to write out. I have found that reducing this tends to smooth out bursty spikes. However, see: http://www.westnet.com/~gsmith/content/linux-pdflush.htm which indicates that kernel may try to defeat you here... Have a nice day, -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > Patriotism is when love of your own people comes first; nationalism, > when hate for people other than your own comes first. > - Charles de Gaulle
Attachment:
signature.asc
Description: Digital signature
