On 2023/04/05 19:43, Karel Zak wrote:
On Wed, Apr 05, 2023 at 03:12:38PM +0900, Akihiko Odaki wrote:
w we can merge
Before this change, lscpu_cputype held topology information.
I do not understand why this is a problem. The topology (number of
threads, cores, etc.) is specific to the type of CPU, right?
I guess the sibling maps in kernel describes this.
This
design is incompatible with heterogenous configurations where there are
several CPU types.
This design has been motivated by heterogenous systems :-)
Model name: Cortex-A53
Model: 4
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Model name: Cortex-A72
Model: 2
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 1
How we can display "Core(s) per socket" if we will not differentiate
between the types?
Well, I think the output is confusing in the same way the output of
""lscpu -p=CPU,Core,Cluster,Socket" is. It says "socket(s): 1" for both
of Cortex-A53 and Cortex-A72, but they are actually in the same socket.
If there is a separate topology section there will be no such confusion.
Regards,
Akihiko Odaki
One problem is that logical IDs of e.g. clusters overlap across
different CPU types. For example, consider a
1-socket/2-cluster/1-core/1-thread system. One of the clusters has
"P-cores", and the other has "E-cores". P-cores and E-cores have
different CPU types. Before this change,
"lscpu -p=CPU,Core,Cluster,Socket" output something like the following
for the system:
0,0,0,0
1,0,0,0
Note that lscpu assigns the same core/cluster ID for the two CPUs
although they are actually in different cores and clusters.
To fix the inconsistency and ambiguity of such IDs, move the topology
information from lscpu_cputype to lscpu_cxt. For the earlier example,
the output will change as follows:
0,0,0,0
1,1,1,0
Then we need to fix _this output_, but not ignore cputypes for whole
lscpu.
This also changes how the topology is described in the summary which
lscpu prints when it is executed with no arguments. Before this change,
the topology information was associated with CPU types, but the
topology information is shown in a separate section now.
I don't like it. We had this output before lscpu rewrite and was pretty
confusing for users.
Karel
