Add topo.nr_cpu_ids() to Topology crate #379
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In some cases, a host may have an odd topology where there are gaps in CPU IDs (including between possible CPUs). A common pattern in schedulers is to perform allocations for every possible CPU ID, such as creating a per-cpu DSQ. In order to avoid confusing schedulers, let's track the maximum CPU ID on a system so that we can return the number of CPU IDs on the system which is inclusive of gaps. We also update scx_rustland in this change to accommodate the fact that we no longer export nr_cpus_possible() from TopologyMap. Signed-off-by: David Vernet <[email protected]>
In scx_rusty, we're currently using topo.nr_cpus_possible() to determine how many possible CPU IDs we could have on the system. scx_rusty already accounts for offlined CPUs, so to properly support systems whose disabled CPUs may be in the middle of the range of possible CPU IDs, let's instead use topo.nr_cpu_ids(). Signed-off-by: David Vernet <[email protected]>
In scx_rlfifo, we're currently using topo.nr_cpus_possible() to determine how many possible CPU IDs we could have on the system. To properly support systems whose disabled CPUs may be in the middle of the range of possible CPU IDs, let's instead use topo.nr_cpu_ids() so that we don't accidentally dispatch to an invalid DSQ. Signed-off-by: David Vernet <[email protected]>
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htejun
approved these changes
Jun 21, 2024
arighi
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Jun 21, 2024
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In some cases, a host may have an odd topology where there are gaps in
CPU IDs (including between possible CPUs). A common pattern in
schedulers is to perform allocations for every possible CPU ID, such as
creating a per-cpu DSQ. In order to avoid confusing schedulers, let's
track the maximum CPU ID on a system so that we can return the number of
CPU IDs on the system which is inclusive of gaps.
This closes the loop on the discussion in #281 (review).