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Disable CPU C-States other than C1 (#16703)

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Why I did it
Networking devices need to be responsive. Such responsiveness is harmed when the CPU change state.
There is a latency penalty when a CPU is idle (e.g C2) and need to exit this state to come back to C1 state.
To prevent this from happening the CPU should be forced to remain in C1 state.

How I did it
Generalize the cstate forcing to C1 to all Arista products.
This is done by adding processor.max_cstate=1 to the kernel cmdline for all CPUs.
Additionally Intel CPUs also need intel_idle.max_cstate=0 to fallback to the acpi_idle driver.

How to verify it
Check that processor.max_cstate=1 is present on the cmdline for AMD CPUs
Check that both processor.max_cstate=1 and intel_idle.max_cstate=0 are present on the cmdline for Intel CPUs
This commit is contained in:
Samuel Angebault 2023-10-14 05:24:39 +02:00 committed by mssonicbld
parent d504600c9f
commit cf4f06d1c5
1 changed files with 8 additions and 2 deletions
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10
files/Aboot/boot0.j2
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@ -611,6 +611,14 @@ write_platform_specific_cmdline() {
aboot_machine=arista_7280cr3mk_32p4
flash_size=7382
fi
# disable cpu c-state other than C1
local cpuvendor="$(sed -nr 's/vendor_id[\t ]*: (.*)/\1/p' /proc/cpuinfo | head -n 1)"
cmdline_add processor.max_cstate=1
if [ "$cpuvendor" = "GenuineIntel" ]; then
cmdline_add intel_idle.max_cstate=0
fi
if in_array "$platform" "rook" "magpie" "woodpecker" "sprucefish"; then
cmdline_add tsc=reliable
cmdline_add pcie_ports=native
@ -621,7 +629,6 @@ write_platform_specific_cmdline() {
if in_array "$platform" "rook" "sprucefish"; then
cmdline_add iommu=on
cmdline_add intel_iommu=on
cmdline_add intel_idle.max_cstate=0
read_system_eeprom
fi
if in_array "$platform" "rook"; then
@ -639,7 +646,6 @@ write_platform_specific_cmdline() {
read_system_eeprom
fi
if in_array "$platform" "lorikeet" "hedgehog"; then
cmdline_add processor.max_cstate=1
cmdline_add reassign_prefmem
read_system_eeprom
fi