global percpu data rfc v1 #8330
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Similar to commit 6316f78 ("Merge branch 'support-global-data'"), this patch introduces global percpu data in order to define global percpu variable like "DEFINE_PER_CPU()"[0] macro. Then, in bpf, it is able to define global percpu variable like \#define PERCPU_BASE_SECTION SEC(".data..percpu") \#define DEFINE_PERCPU_VAR(typ, name) \ PERCPU_BASE_SECTION __typeof__(typ) name DEFINE_PERCPU_VAR(int, percpu_data); With this patch, retsnoop[1] and bpflbr[2] are able to simplify the bpf code of lbrs from static struct perf_branch_entry lbrs[1][MAX_LBR_ENTRIES] SEC(".data.lbrs"); to static struct perf_branch_entry lbrs[MAX_LBR_ENTRIES] SEC(".data..percpu.lbrs"); and it's unnecessary to get cpu by "bpf_get_smp_processor_id()" helper. Furthermore, by reusing the maps of global percpu data, data is simpler to be shared between tail callers&callees and freplace callers&callees than percpu_array maps. Links: [0] https://github.com/torvalds/linux/blob/fbfd64d25c7af3b8695201ebc85efe90be28c5a3/include/linux/percpu-defs.h#L114 [1] https://github.com/anakryiko/retsnoop [2] https://github.com/Asphaltt/bpflbr Signed-off-by: Leon Hwang <[email protected]>
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If the arch does not support percpu insn, skip this case. cd tools/testing/selftests/bpf; ./test_progs -t global_percpu_data 124 global_percpu_data_init:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Leon Hwang <[email protected]>
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