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Subject: Re: [hwloc-users] Thread core affinity
From: Gabriele Fatigati (g.fatigati_at_[hidden])
Date: 2011-08-01 09:29:29


Ok,

now it's more clear. Just a little question. Why in a NUMA machine, PU# are
sequential (page 17), and in a non NUMA machine are not sequential? ( page
16)

2011/8/1 Brice Goglin <Brice.Goglin_at_[hidden]>

> **
> You're confusing object types with index types.
>
> PU is an object type, like Core, Socket, ... "logical processor" is a
> generic name for cores when there's no SMT, hardware threads when there's
> SMT/Hyperthreading, ... PU is basically the smallest thing that can run a
> software thread.
>
> "P#" is just the way you're numbering object, it works for PU and for other
> object types.
>
> Any object of any type can be identified through a unique logical index,
> and possibly non-unique physical index.
>
> We don't often use the name "logical processor" because it's indeed
> confusing. "Processing Unit" is less confusing, that's why it's the official
> name for the smallest objects in hwloc.
>
> Brice
>
>
>
>
>
>
>
> Le 01/08/2011 15:04, Gabriele Fatigati a écrit :
>
> Hi Brice,
>
> you said:
>
> "PU P#0" means "PU object with physical index 0".
> "P#" prefix means "physical index".
>
> But from the hwloc manual, page 58:
>
>
> HWLOC_OBJ_PU: Processing Unit, or (Logical) Processor..
>
>
> but it is in conflict with what you said :(
>
>
> 2011/8/1 Brice Goglin <Brice.Goglin_at_[hidden]>
>
>> "PU P#0" means "PU object with physical index 0".
>> "P#" prefix means "physical index".
>> "L#" prefix means "logical index" (the one you want to use in
>> get_obj_by_type).
>> Use -l or -p to switch from one to the other in lstopo.
>>
>> Brice
>>
>>
>>
>> Le 01/08/2011 14:47, Gabriele Fatigati a écrit :
>>
>> Hi Brice,
>>
>> so, if I inderstand well, PU P# numbers are not the same specified as
>> HWLOC_OBJ_PU flag?
>>
>> 2011/8/1 Brice Goglin <Brice.Goglin_at_[hidden]>
>>
>>> Le 01/08/2011 12:16, Gabriele Fatigati a écrit :
>>> > Hi,
>>> >
>>> > reading a hwloc-v1.2-a4 manual, on page 15, i look an example
>>> > with 4-socket 2-core machine with hyperthreading.
>>> >
>>> > Core id's are not exclusive as said before. PU's id are exclusive but
>>> > not physically sequential (I suppose)
>>> >
>>> > PU P#0 is in socket P#0 on Core P#0. PU P#1 is in another socket!
>>>
>>> These indexes are "physical indexes" (that's the default in the
>>> graphical lstopo output). But we may want to make that clearer in the
>>> doc.
>>>
>>> Brice
>>>
>>>
>>
>>
>> --
>> Ing. Gabriele Fatigati
>>
>> Parallel programmer
>>
>> CINECA Systems & Tecnologies Department
>>
>> Supercomputing Group
>>
>> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>>
>> www.cineca.it Tel: +39 051 6171722
>>
>> g.fatigati [AT] cineca.it
>>
>>
>>
>
>
> --
> Ing. Gabriele Fatigati
>
> Parallel programmer
>
> CINECA Systems & Tecnologies Department
>
> Supercomputing Group
>
> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>
> www.cineca.it Tel: +39 051 6171722
>
> g.fatigati [AT] cineca.it
>
>
>

-- 
Ing. Gabriele Fatigati
Parallel programmer
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it                    Tel:   +39 051 6171722
g.fatigati [AT] cineca.it