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gso321
n00b
Joined: 02 Jan 2023
Posts: 15
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 Posted: Wed Mar 15, 2023 1:13 am Post subject: PGO kernel using GCC? |
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Does anyone here have manage to use Profile Guided Optimizations for modern Linux kernel with GCC?
Most websites i seen are either outdated or not specific like coolypf and Yuan's paper. I decided to follow Yuan's approach till i got stuck part at "a shell script is used to collect
profile data files from DebugFS" in phase 2. My original question was going to be "What is the shell script is used to collect profile data files from DebugFS?" but i didn't want to get blamed for taking the XY problem.
To be more specific, i used sys-kernel/gentoo-sources-6.2.5 with experimental use flag. I turn on CONFIG_GCOV_KERNEL and CONFIG_GCOV_PROFILE_ALL, complied the kernel, then reboot. The *.gcda files show up in /sys/kernel/debug/gcov/usr/src/linux. I disable CONFIG_GCOV_KERNEL and CONFIG_GCOV_PROFILE_ALL. Then i edit | Code: | | KCFLAGS = "fprofile-use -fprofile-correction" |
and, after compiling, the problem occurs with | Code: | | error: ‘/usr/src/linux-6.2.5-gentoo/tools/objtool/weak.gcda’ profile count data file not found |
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kuhitori
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Joined: 24 May 2023
Posts: 1
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| Posted: Wed May 24, 2023 12:00 pm Post subject: |
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gso321, I use 6.1.28 wtih PGO, you need to copy the .gcda files to /usr/src/kernel before compiling.
Please read this for proper use of GCC PGO
Kuhitori |
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