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machine: Prefer cores over sockets in smp parsing since 6.2

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In the real SMP hardware topology world, it's much more likely that
we have high cores-per-socket counts and few sockets totally. While
the current preference of sockets over cores in smp parsing results
in a virtual cpu topology with low cores-per-sockets counts and a
large number of sockets, which is just contrary to the real world.

Given that it is better to make the virtual cpu topology be more
reflective of the real world and also for the sake of compatibility,
we start to prefer cores over sockets over threads in smp parsing
since machine type 6.2 for different arches.

In this patch, a boolean "smp_prefer_sockets" is added, and we only
enable the old preference on older machines and enable the new one
since type 6.2 for all arches by using the machine compat mechanism.

Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210929025816.21076-10-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Yanan Wang 2021-09-29 10:58:09 +08:00 • committed by Paolo Bonzini
parent bbb0c0ec6d
commit 4a0af2930a
9 changed files with 60 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

35
hw/i386/pc.c
View file

@ -716,6 +716,7 @@ void pc_acpi_smi_interrupt(void *opaque, int irq, int level)
*/
static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
{
MachineClass *mc = MACHINE_GET_CLASS(ms);
unsigned cpus = config->has_cpus ? config->cpus : 0;
unsigned sockets = config->has_sockets ? config->sockets : 0;
unsigned dies = config->has_dies ? config->dies : 0;
@ -726,7 +727,7 @@ static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
/* directly default dies to 1 if it's omitted */
dies = dies > 0 ? dies : 1;
/* compute missing values, prefer sockets over cores over threads */
/* compute missing values based on the provided ones */
if (cpus == 0 && maxcpus == 0) {
sockets = sockets > 0 ? sockets : 1;
cores = cores > 0 ? cores : 1;
@ -734,14 +735,30 @@ static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
} else {
maxcpus = maxcpus > 0 ? maxcpus : cpus;
if (sockets == 0) {
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
sockets = maxcpus / (dies * cores * threads);
} else if (cores == 0) {
threads = threads > 0 ? threads : 1;
cores = maxcpus / (sockets * dies * threads);
} else if (threads == 0) {
if (mc->smp_prefer_sockets) {
/* prefer sockets over cores before 6.2 */
if (sockets == 0) {
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
sockets = maxcpus / (dies * cores * threads);
} else if (cores == 0) {
threads = threads > 0 ? threads : 1;
cores = maxcpus / (sockets * dies * threads);
}
} else {
/* prefer cores over sockets since 6.2 */
if (cores == 0) {
sockets = sockets > 0 ? sockets : 1;
threads = threads > 0 ? threads : 1;
cores = maxcpus / (sockets * dies * threads);
} else if (sockets == 0) {
threads = threads > 0 ? threads : 1;
sockets = maxcpus / (dies * cores * threads);
}
}
/* try to calculate omitted threads at last */
if (threads == 0) {
threads = maxcpus / (sockets * dies * cores);
}
}

1
hw/i386/pc_piix.c
View file

@ -432,6 +432,7 @@ static void pc_i440fx_6_1_machine_options(MachineClass *m)
m->is_default = false;
compat_props_add(m->compat_props, hw_compat_6_1, hw_compat_6_1_len);
compat_props_add(m->compat_props, pc_compat_6_1, pc_compat_6_1_len);
m->smp_prefer_sockets = true;
}
DEFINE_I440FX_MACHINE(v6_1, "pc-i440fx-6.1", NULL,

1
hw/i386/pc_q35.c
View file

@ -372,6 +372,7 @@ static void pc_q35_6_1_machine_options(MachineClass *m)
m->alias = NULL;
compat_props_add(m->compat_props, hw_compat_6_1, hw_compat_6_1_len);
compat_props_add(m->compat_props, pc_compat_6_1, pc_compat_6_1_len);
m->smp_prefer_sockets = true;
}
DEFINE_Q35_MACHINE(v6_1, "pc-q35-6.1", NULL,