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authorEric Dumazet <dada1@cosmosbay.com>2006-12-13 00:35:45 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-13 09:05:55 -0800
commitcd7175edf963a92b2c3cd491d3e34afd357e7284 (patch)
tree72c0445ef456f005e26d04568b5a07e8ed95e084 /REPORTING-BUGS
parentf988443a84528bd30c2f474efa5e2c511959f19b (diff)
[PATCH] Optimize calc_load()
calc_load() is called by timer interrupt to update avenrun[]. It currently calls nr_active() at each timer tick (HZ per second), while the update of avenrun[] is done only once every 5 seconds. (LOAD_FREQ=5 Hz) nr_active() is quite expensive on SMP machines, since it has to sum up nr_running and nr_uninterruptible of all online CPUS, bringing foreign dirty cache lines. This patch is an optimization of calc_load() so that nr_active() is called only if we need it. The use of unlikely() is welcome since the condition is true only once every 5*HZ time. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: "Siddha, Suresh B" <suresh.b.siddha@intel.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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