Messages in this thread | | | Date | Tue, 24 Jan 2012 16:12:21 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v2] proc: speedup /proc/stat handling |
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On Wed, 25 Jan 2012 01:01:23 +0100 Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On a typical 16 cpus machine, "cat /proc/stat" gives more than 4096 > bytes, and is slow :
It is pretty bad:
akpm:/usr/src/25> time (for i in $(seq 1000); do; cat /proc/self/stat > /dev/null; done) (; for i in $(seq 1000); do; cat /proc/self/stat > /dev/null; done; ) 0.05s user 0.94s system 29% cpu 3.367 total
(29% CPU?)
> # strace -T -o /tmp/STRACE cat /proc/stat | wc -c > 5826 > # grep "cpu " /tmp/STRACE > read(0, "cpu 1949310 19 2144714 12117253"..., 32768) = 5826 <0.001504> >
Did you measure the improvement from this patch?
> Thats partly because show_stat() must be called twice since initial > buffer size is too small (4096 bytes for less than 32 possible cpus) > > Fix this by : > > 1) Taking into account nr_irqs in the initial buffer sizing. > > 2) Using ksize() to allow better filling of initial buffer.
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