On 3/3/25 15:40, Yicong Yang wrote:
On 2025/3/3 19:16, Sudeep Holla wrote:
On Mon, Mar 03, 2025 at 10:56:12AM +0100, Pierre Gondois wrote:
On 2/28/25 20:06, Sudeep Holla wrote:
Ditto as previous patch, can get rid if it is default 1.
On non-SMT platforms, not calling cpu_smt_set_num_threads() leaves
cpu_smt_num_threads uninitialized to UINT_MAX:
smt/active:0
smt/control:-1
If cpu_smt_set_num_threads() is called:
active:0
control:notsupported
So it might be slightly better to still initialize max_smt_thread_num.
Sure, what I meant is to have max_smt_thread_num set to 1 by default is
that is what needed anyways and the above code does that now.
Why not start with initialised to 1 instead ?
Of course some current logic needs to change around testing it for zero.
I think there would still be a way to check against the default value.
If we have:
unsigned int max_smt_thread_num = 1;
then on a platform with 2 threads, the detection condition would trigger:
xa_for_each(&hetero_cpu, hetero_id, entry) {
if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) <----
(entry->thread_num=2) and (max_smt_thread_num=1)
pr_warn_once("Heterogeneous SMT topology is partly
supported by SMT control\n");
so we would need an additional variable:
bool is_initialized = false;
Sure, we could do that or skip the check if max_smt_thread_num == 1 ?
I mean
if (entry->thread_num != max_smt_thread_num && max_smt_thread_num != 1)
I think it will be problematic if we parse:
- first a CPU with 1 thread
- then a CPU with 2 threads
in that case we should detect the 'Heterogeneous SMT topology',
but we cannot because we don't know whether max_smt_thread_num=1
because 1 is the default value or we found a CPU with one thread.
