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The struct dump_regs contains 512 bytes of cache_regs, meaning the two values in perf_sample contribute 1088 bytes of its total 1384 bytes size. Initializing this much memory has a cost reported by Tavian Barnes <tavianator@tavianator.com> as about 2.5% when running `perf script --itrace=i0`: https://lore.kernel.org/lkml/d841b97b3ad2ca8bcab07e4293375fb7c32dfce7.1736618095.git.tavianator@tavianator.com/ Adrian Hunter <adrian.hunter@intel.com> replied that the zero initialization was necessary and couldn't simply be removed. This patch aims to strike a middle ground of still zeroing the perf_sample, but removing 79% of its size by make user_regs and intr_regs optional pointers to zalloc-ed memory. To support the allocation accessors are created for user_regs and intr_regs. To support correct cleanup perf_sample__init and perf_sample__exit functions are created and added throughout the code base. Signed-off-by: Ian Rogers <irogers@google.com> Link: https://lore.kernel.org/r/20250113194345.1537821-1-irogers@google.com Signed-off-by: Namhyung Kim <namhyung@kernel.org>
71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include "arm64-frame-pointer-unwind-support.h"
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#include "callchain.h"
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#include "event.h"
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#include "perf_regs.h" // SMPL_REG_MASK
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#include "unwind.h"
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#include <string.h>
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#define perf_event_arm_regs perf_event_arm64_regs
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#include "../../arch/arm64/include/uapi/asm/perf_regs.h"
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#undef perf_event_arm_regs
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struct entries {
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u64 stack[2];
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size_t length;
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};
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static bool get_leaf_frame_caller_enabled(struct perf_sample *sample)
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{
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struct regs_dump *regs;
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if (callchain_param.record_mode != CALLCHAIN_FP)
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return false;
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regs = perf_sample__user_regs(sample);
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return regs->regs && regs->mask & SMPL_REG_MASK(PERF_REG_ARM64_LR);
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}
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static int add_entry(struct unwind_entry *entry, void *arg)
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{
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struct entries *entries = arg;
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entries->stack[entries->length++] = entry->ip;
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return 0;
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}
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u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thread, int usr_idx)
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{
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int ret;
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struct entries entries = {};
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struct regs_dump old_regs, *regs;
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if (!get_leaf_frame_caller_enabled(sample))
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return 0;
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/*
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* If PC and SP are not recorded, get the value of PC from the stack
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* and set its mask. SP is not used when doing the unwinding but it
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* still needs to be set to prevent failures.
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*/
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regs = perf_sample__user_regs(sample);
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memcpy(&old_regs, regs, sizeof(*regs));
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if (!(regs->mask & SMPL_REG_MASK(PERF_REG_ARM64_PC))) {
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regs->cache_mask |= SMPL_REG_MASK(PERF_REG_ARM64_PC);
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regs->cache_regs[PERF_REG_ARM64_PC] = sample->callchain->ips[usr_idx+1];
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}
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if (!(regs->mask & SMPL_REG_MASK(PERF_REG_ARM64_SP))) {
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regs->cache_mask |= SMPL_REG_MASK(PERF_REG_ARM64_SP);
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regs->cache_regs[PERF_REG_ARM64_SP] = 0;
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}
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ret = unwind__get_entries(add_entry, &entries, thread, sample, 2, true);
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memcpy(regs, &old_regs, sizeof(*regs));
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if (ret || entries.length != 2)
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return ret;
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return callchain_param.order == ORDER_CALLER ? entries.stack[0] : entries.stack[1];
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}
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