http://www.erlang.org/doc/man/erl.html#+S
+S TotalSchedulers:OnlineSchedulers On Wed, Aug 14, 2013 at 9:57 AM, Guido Medina <guido.med...@temetra.com>wrote: > Hi Matthew, > > It is a bit confusing, cause let's say "+S C:T" is defined as: > > C = Physical cores? > T = Total threads or total - physical cores? > > Is it a sum of or the physical cores and total of threads? That's the > confusing part, let's say you have a server with 8 physical cores with no > hyper threading, so total threads is also 8, would that still be "+S 4:4", > "+S 8:8" or "+S 8:0" > > Thanks, > > Guido. > > > On 14/08/13 15:41, Matthew Von-Maszewski wrote: > >> "threads=8" is the key phrase … +S 4:4 >> >> On Aug 14, 2013, at 10:04 AM, Guido Medina <guido.med...@temetra.com> >> wrote: >> >> For the following information should it be +S 4:4 or +S 4:8? >>> >>> root@somehost# lshw -C processor >>> *-cpu >>> description: CPU >>> product: Intel(R) Core(TM) i7 CPU 930 @ 2.80GHz >>> vendor: Intel Corp. >>> physical id: 4 >>> bus info: cpu@0 >>> version: Intel(R) Core(TM) i7 CPU 930 @ 2.80GHz >>> serial: To Be Filled By O.E.M. >>> slot: CPU 1 >>> size: 1600MHz >>> capacity: 1600MHz >>> width: 64 bits >>> clock: 133MHz >>> capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae >>> mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse >>> sse2 ss ht tm pbe syscall nx rdtscp constant_tsc arch_perfmon pebs bts >>> rep_good nopl xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl >>> vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm ida dtherm >>> tpr_shadow vnmi flexpriority ept vpid cpufreq >>> configuration: cores=4 enabledcores=4 threads=8 >>> >>> Thanks, >>> >>> Guido. >>> >>> On 14/08/13 01:38, Matthew Von-Maszewski wrote: >>> >>>> ** The following is copied from Basho's leveldb wiki page: >>>> >>>> https://github.com/basho/**leveldb/wiki/Riak-tuning-1<https://github.com/basho/leveldb/wiki/Riak-tuning-1> >>>> >>>> >>>> >>>> Summary: >>>> >>>> leveldb has a higher read and write throughput in Riak if the Erlang >>>> scheduler count is limited to half the number of CPU cores. Tests have >>>> demonstrated improvements of 15% to 80% greater throughput. >>>> >>>> The scheduler limit is set in the vm.args file: >>>> >>>> +S x:x >>>> >>>> where "x" is the number of schedulers Erlang may use. Erlang's default >>>> value of "x" is the total number of CPUs in the system. For Riak >>>> installations using leveldb, the recommendation is to set "x" to half the >>>> number of CPUs. Virtual environments are not yet tested. >>>> >>>> Example: for 24 CPU system >>>> >>>> +S 12:12 >>>> >>>> Discussion: >>>> >>>> We have tested a limited number of CPU configurations and customer >>>> loads. In all cases, there is a performance increase when the +S option is >>>> added to the vm.args file to reduce the number of Erlang schedulers. The >>>> working hypothesis is that the Erlang schedulers perform enough "busy wait" >>>> work that they always create context switch away from leveldb when leveldb >>>> is actually the only system task with real work. >>>> >>>> The tests included 8 CPU (no hyper threading, physical cores only) and >>>> 24 CPU (12 physical cores with hyper threading) systems. All were 64bit >>>> Intel platforms. Generalized findings: >>>> >>>> • servers running higher number of vnodes (64) had larger >>>> performance gains than those with fewer (8) >>>> • servers running SSD arrays had larger performance gains than >>>> those running SATA arrays >>>> • Get and Write operations showed performance gains, 2i query >>>> operations (leveldb iterators) were unchanged >>>> • Not recommended for servers with less than 8 CPUs (go no >>>> lower than +S 4:4) >>>> >>>> Performance improvements were as high as 80% over extended, heavily >>>> loaded intervals on servers with SSD arrays and 64 vnodes. No test resulted >>>> in worse performance due to the addition of +S x:x. >>>> >>>> The +S x:x configuration change does not have to be implemented >>>> simultaneously to an entire Riak cluster. The change may be applied to a >>>> single server for verification. Steps: update the vm.args file, then >>>> restart the Riak node. Erlang command line changes to schedules were >>>> ineffective. >>>> >>>> This configuration change has been running in at least one large, >>>> multi-datacenter production environment for several months. >>>> >>>> >>>> ______________________________**_________________ >>>> riak-users mailing list >>>> riak-users@lists.basho.com >>>> http://lists.basho.com/**mailman/listinfo/riak-users_**lists.basho.com<http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com> >>>> >>> >>> ______________________________**_________________ >>> riak-users mailing list >>> riak-users@lists.basho.com >>> http://lists.basho.com/**mailman/listinfo/riak-users_**lists.basho.com<http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com> >>> >> > > ______________________________**_________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/**mailman/listinfo/riak-users_**lists.basho.com<http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com> > -- Sean Cribbs <s...@basho.com> Software Engineer Basho Technologies, Inc. http://basho.com/
_______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
