Messages in this thread | | | Subject | Re: [PATCH] : A better approach to compute int_sqrt in lib/int_sqrt.c | From | Peter Zijlstra <> | Date | Thu, 17 Jul 2008 20:26:55 +0200 |
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On Wed, 2008-07-16 at 14:35 -0700, Soumyadip Das Mahapatra wrote:
> 0 It is better because > o it uses only one loop instead of two > o contains no division operator (older version has two) > which are surely comparatively slow task in computer
As Lennart has said, gcc is smart enough to transform a division by a power-of-two into shifts.
> 0 Currently find . -name '*.[ch]' | xargs grep int_sqrt gives me this > .... > ./fs/nfs/write.c: nfs_congestion_kb = (16*int_sqrt(totalram_pages)) << (PAGE_SHIFT-10); > ./drivers/video/fbmon.c: h_period = int_sqrt(h_period); > ./mm/page_alloc.c: min_free_kbytes = int_sqrt(lowmem_kbytes * 16); > ./mm/oom_kill.c: s = int_sqrt(cpu_time); > ./mm/oom_kill.c: s = int_sqrt(int_sqrt(run_time)); > ....
fs/nfs/write.c is init code mm/page_alloc.c is also init code mm/oom_kill.c isn't a hot path
which leaves the fbmon case, which after a quick peek is setup code, so not a hot path either.
So while that doesn't preclude us from changing it if you can indeed show its a better implementation, its not on anybodies hit-list.
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