On Apr 24, 2007, at 3:51 AM, Bert Wesarg wrote:
>>> to the processor_id. That can be queried by the api. But to support
>>> SMT,
>>> it would be necessary to extend it to a (socket,core,thread) tuple.
>>
>> I still don't understand this last statement.
> Ok, if the current (socket,core) plpa code will ever hit a machine
> with
> enabled SMT/HTT, or whatever its called today, the code will find
> multiple
> (socket,core) tuples for one processor ID and so breaking the ont-
> to-one
> mapping. Because a core have threads, and therefor multiple virtual
> processor ids. But I can't prove it, because I don't have access to
> such a
> machine or unless someone sends a cpu topology with enabled HTT/SMT
> (see
> the Call for Help message).
Ah, I think I'm starting to understand.
I think you meant to say that a single (socket,core) tuple would map
to multiple processor ID's.
Regardless, you're right: it breaks the one-to-one mapping.
I have hyper-threading enabled on my lab machines, but they're an
older kernel (RHEL4U3 -- 2.6.9-based kernel). They're 2 socket Intel
x86_64 machines, each socket with 2 cores (total of 4 cores).
But I tried to grab the data anyway:
/sys % sudo tar cjf /tmp/cpu-topology.tar.bz2 devices/system/{cpu/
cpu*/topology/*,node/node*/cpu*}
tar: devices/system/node/node0/cpumap: File shrank by 4093 bytes;
padding with zeros
tar: Error exit delayed from previous errors
Hmm. Got any ideas?
My /sys/devices/system/cpu/ has 8 directories (because HT is enabled;
I never bothered to turn it off): cpu0 through cpu7. Each of those
directories is empty (assumedly because the kernel is too old).
Since it's a UMA machine, I only have /sys/devices/system/node/
node0. In there, it has sym links to the 8 cpu* directories and
three additional files:
/sys/devices/system/node/node0 % ls
cpu0@ cpu2@ cpu4@ cpu6@ cpumap numastat
cpu1@ cpu3@ cpu5@ cpu7@ meminfo
Here's the contents of those three files:
/sys/devices/system/node/node0 % cat cpumap
ff
/sys/devices/system/node/node0 % cat meminfo
Node 0 MemTotal: 5242880 kB
Node 0 MemFree: 278968 kB
Node 0 MemUsed: 4963912 kB
Node 0 Active: 1285488 kB
Node 0 Inactive: 2031128 kB
Node 0 HighTotal: 0 kB
Node 0 HighFree: 0 kB
Node 0 LowTotal: 5242880 kB
Node 0 LowFree: 278968 kB
Node 0 HugePages_Total: 0
Node 0 HugePages_Free: 0
/sys/devices/system/node/node0 % cat numastat
numa_hit 3705213152
numa_miss 0
numa_foreign 0
interleave_hit 383843
local_node 3705213152
other_node 0
--
Jeff Squyres
Cisco Systems
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