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MEDIUM: cpu-topo: prefer grouping by CCX for "performance" and "efficiency"

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Most of the time, machines made of multiple CPU types use the same L3
for them, and grouping CPUs by frequencies to form groups doesn't bring
any value and on the opposite can impair the incoming connection balancing.
This choice of grouping by cluster was made in order to constitute a good
choice on homogenous machines as well, so better rely on the per-CCX
grouping than the per-cluster one in this case. This will create less
clusters on machines where it counts without affecting other ones.

It doesn't seem necessary to change anything for the "resource" policy
since it selects a single cluster.
This commit is contained in:
Willy Tarreau 2025-05-13 16:20:53 +02:00
parent 70b0dd6b0f
commit 158da59c34
2 changed files with 11 additions and 7 deletions
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6
doc/configuration.txt
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@ -1992,7 +1992,7 @@ cpu-policy <policy>
systems, per thread-group. The number of thread-groups,
if not set, will be set to 1.
- efficiency exactly like group-by-cluster below, except that CPU
- efficiency exactly like "group-by-ccx" below, except that CPU
clusters composed of cores whose performance is more
than 25% above that of the next less performant one are
evicted. These are typically "big" or "performance"
@ -2098,7 +2098,7 @@ cpu-policy <policy>
laptops and desktop machines used by developers and
admins to validate setups.
- performance exactly like group-by-cluster above, except that CPU
- performance exactly like "group-by-ccx" above, except that CPU
clusters composed of cores whose performance is less
than 80% of those of the next more performant one are
evicted. These are typically "little" or "efficient"
@ -2110,7 +2110,7 @@ cpu-policy <policy>
auxiliary tools such as load generators and monitoring
tools.
- resource this is like group-by-cluster above, except that only
- resource this is like "group-by-cluster" above, except that only
the smallest and most efficient CPU cluster will be
used, while all other ones will be ignored. This can be
used to limit the resource usage to the strict minimum

12
src/cpu_topo.c
View File

@ -1353,8 +1353,10 @@ static int cpu_policy_performance(int policy, int tmin, int tmax, int gmin, int
cpu_cluster_reorder_by_index(ha_cpu_clusters, cpu_topo_maxcpus);
/* and finish using the group-by-cluster strategy */
return cpu_policy_group_by_cluster(policy, tmin, tmax, gmin, gmax, err);
/* and finish using the group-by-ccx strategy, which will split around
* L3 rather than just cluster types.
*/
return cpu_policy_group_by_ccx(policy, tmin, tmax, gmin, gmax, err);
}
/* the "efficiency" cpu-policy:
@ -1395,8 +1397,10 @@ static int cpu_policy_efficiency(int policy, int tmin, int tmax, int gmin, int g
cpu_cluster_reorder_by_index(ha_cpu_clusters, cpu_topo_maxcpus);
/* and finish using the group-by-cluster strategy */
return cpu_policy_group_by_cluster(policy, tmin, tmax, gmin, gmax, err);
/* and finish using the group-by-ccx strategy, which will split around
* L3 rather than just cluster types.
*/
return cpu_policy_group_by_ccx(policy, tmin, tmax, gmin, gmax, err);
}