On Thu, Aug 11, 2011 at 14:27, Nikos Chantziaras <[email protected]> wrote: > On 08/11/2011 09:56 AM, Pandu Poluan wrote: >> >> Just wondering, is it possible to specify a custom timer frequency? >> E.g., HZ=500 instead of one of the canned values (100, 250, 300, >> 1000). > > It is possible, but it's a bad idea because non-standard values can result > in driver breakage. Some code assumes specific timer granularities (100Hz = > 10ms, 250Hz = 4ms, etc). This usually happens with values above 1000Hz, so > it might be possible to experiment with non-standard sub-1000Hz values. > > But why do you want a custom value anyway? >
Well, for a firewall, I've calculated (gathered and extrapolated from a lot of sources), the latency per-packet is usually less than 1 ms, at worst still less than 2 ms. Thus, setting the timer freq to 100 Hz (as suggested for 'normal' server load) means the timeslice is way too long (10 ms per time slice). So, I speculate that better -- and uniform -- performance will be achieved with a timer freq of 500 Hz. Of course, this is a wild speculation/guess from me. I never quite understand netfilter/xtables' relation to the timeslices, so I may be talking nonsense :-) Rgds, -- FdS Pandu E Poluan ~ IT Optimizer ~ • Blog : http://pepoluan.tumblr.com • Linked-In : http://id.linkedin.com/in/pepoluan
