setting GRUB_CMDLINE_LINUX, example usage of perf c2c #420
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perfrunbook/debug_hw_perf.md
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| @@ -230,6 +231,11 @@ the samples directly, you can use the [Arm SPE Parser](https://gitlab.arm.com/te | |||
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| Be aware that SPE produces a large of volume of data (many GBs) if the sampling period is low and you collect the data over a long time. | |||
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| ### Capturing cache coherence issues | |||
| The `perf c2c` command can be used to analyze cache coherence issues and false sharing in multi-core systems. | |||
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Please add info that this uses SPE on Graviton, which is only available on metal instances, and requires loading the SPE driver (apt-get install linux-modules-extra-$(uname -r) && modprobe arm_spe_pmu).
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Do we need to add for AL as well?
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The existing text does have instructions to load the SPE driver. So, not adding those again in this PR.
perfrunbook/debug_hw_perf.md
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| @@ -213,7 +213,8 @@ On Ubuntu to enable SPE requires four extra steps | |||
| # Install the arm_spe_pmu.ko module | |||
| sudo apt install linux-modules-extra-$(uname -r) | |||
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| # Add kpti=off to the kernel boot command line | |||
| # Add kpti=off to the kernel boot command line: GRUB_CMDLINE_LINUX, to set it for all the installed kernels. | |||
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"Modify the kernel boot arguments for all installed kernels by adding kpti=off to GRUB_CMDLINE_LINUX in /etc/default/grub"
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Can we maybe provide a quick inline change cmd to it? something like:
sed -i -E 's/^(GRUB_CMDLINE_LINUX=".*)"/\1 kpti=off"/g' /etc/default/grub
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The sed command is tricky to get right in all situations, e.g. what if the line already sets kpti, or there is no GRUB_CMDLINE_LINUX line?
It's better to explain what to do so the user knows where/what to modify, rather than copy/paste something harder to understand and potentially faulty or suboptimal.
Signed-off-by: Rama Malladi <[email protected]>
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This PR adds an example usage of
perf c2cand setting theGRUB_CMDLINE_LINUXfor using SPE.Related issues: #415
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