Messages in this thread | | | Date | Tue, 25 Aug 2015 21:25:41 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC 0/2] Optimize the snmp stat aggregation for large cpus |
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On 08/25/2015 08:03 PM, Eric Dumazet wrote: > On Tue, 2015-08-25 at 13:24 +0530, Raghavendra K T wrote: >> While creating 1000 containers, perf is showing lot of time spent in >> snmp_fold_field on a large cpu system. >> >> The current patch tries to improve by reordering the statistics gathering. >> >> Please note that similar overhead was also reported while creating >> veth pairs https://lkml.org/lkml/2013/3/19/556 >> >> Setup: >> 160 cpu (20 core) baremetal powerpc system with 1TB memory > > I wonder if these kind of results would demonstrate cache coloring > problems on this host. Looks like all the per cpu data are colliding on > same cache lines. >
It could be. My testing on a 128 cpu system with less memory did not incur huge time penalty for 1000 containers. But snmp_fold_field in general had the problem. for e.g. same experiment I had around 15% overhead for snmp_fold reduced to 5% after the patch.
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