From ce37bc52dd6fec7ed290b4cb17e22867dd74f908 Mon Sep 17 00:00:00 2001 From: Daniel Shaulov Date: Tue, 5 May 2020 17:27:33 +0300 Subject: [PATCH] perf inject --jit: Remove //anon mmap events While a JIT is jitting code it will eventually need to commit more pages and change these pages to executable permissions. Typically the JIT will want these colocated to minimize branch displacements. The kernel will coalesce these anonymous mapping with identical permissions before sending an MMAP event for the new pages. This means the mmap event for the new pages will include the older pages. These anonymous mmap events will obscure the jitdump injected pseudo events. This means that the jitdump generated symbols, machine code, debugging info, and unwind info will no longer be used. Observations: When a process emits a jit dump marker and a jitdump file, the perf-xxx.map file represents inferior information which has been superceded by the jitdump jit-xxx.dump file. Further the '//anon*' mmap events are only required for the legacy perf-xxx.map mapping. When attaching to an existing process, the synthetic anon map events are given a time stamp of -1. These should not obscure the jitdump events which have an actual time. Summary: Use thread->priv to store whether a jitdump file has been processed During "perf inject --jit", discard "//anon*" mmap events for any pid which has sucessfully processed a jitdump file. Committer testing: // jitdump case perf record perf inject --jit --input perf.data --output perfjit.data // verify mmap "//anon" events present initially perf script --input perf.data --show-mmap-events | grep '//anon' // verify mmap "//anon" events removed perf script --input perfjit.data --show-mmap-events | grep '//anon' // no jitdump case perf record perf inject --jit --input perf.data --output perfjit.data // verify mmap "//anon" events present initially perf script --input perf.data --show-mmap-events | grep '//anon' // verify mmap "//anon" events not removed perf script --input perfjit.data --show-mmap-events | grep '//anon' Repro: This issue was discovered while testing the initial CoreCLR jitdump implementation. https://github.com/dotnet/coreclr/pull/26897. Signed-off-by: Steve MacLean --- tools/perf/builtin-inject.c | 4 ++-- tools/perf/util/jitdump.c | 38 +++++++++++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+), 2 deletions(-) diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c index 7e124a7b8bfdc4..e3416026ef0f9c 100644 --- a/tools/perf/builtin-inject.c +++ b/tools/perf/builtin-inject.c @@ -292,7 +292,7 @@ static int perf_event__jit_repipe_mmap(struct perf_tool *tool, * if jit marker, then inject jit mmaps and generate ELF images */ ret = jit_process(inject->session, &inject->output, machine, - event->mmap.filename, sample->pid, &n); + event->mmap.filename, event->mmap.pid, &n); if (ret < 0) return ret; if (ret) { @@ -330,7 +330,7 @@ static int perf_event__jit_repipe_mmap2(struct perf_tool *tool, * if jit marker, then inject jit mmaps and generate ELF images */ ret = jit_process(inject->session, &inject->output, machine, - event->mmap2.filename, sample->pid, &n); + event->mmap2.filename, event->mmap2.pid, &n); if (ret < 0) return ret; if (ret) { diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c index e3ccb0ce1938d3..c36d19bb25b350 100644 --- a/tools/perf/util/jitdump.c +++ b/tools/perf/util/jitdump.c @@ -26,6 +26,7 @@ #include "jit.h" #include "jitdump.h" #include "genelf.h" +#include "thread.h" #include #include @@ -749,6 +750,34 @@ jit_detect(char *mmap_name, pid_t pid) return 0; } +static void jit_add_pid(struct machine *machine, pid_t pid) +{ + struct thread *thread = machine__findnew_thread(machine, pid, pid); + + if (!thread) + { + pr_err("jit_add_pid() thread not found\n"); + + return; + } + + thread->priv = (void *) 1; +} + +static bool jit_has_pid(struct machine *machine, pid_t pid) +{ + struct thread *thread = machine__findnew_thread(machine, pid, pid); + + if (!thread) + { + pr_err("jit_has_pid() thread not found\n"); + + return 0; + } + + return (bool) thread->priv; +} + int jit_process(struct perf_session *session, struct perf_data *output, @@ -765,7 +794,15 @@ jit_process(struct perf_session *session, * first, detect marker mmap (i.e., the jitdump mmap) */ if (jit_detect(filename, pid)) + { + /* + * Strip //anon* mmaps if we processed a jitdump for this pid + */ + if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0)) + return 1; + return 0; + } memset(&jd, 0, sizeof(jd)); @@ -784,6 +821,7 @@ jit_process(struct perf_session *session, ret = jit_inject(&jd, filename); if (!ret) { + jit_add_pid(machine, pid); *nbytes = jd.bytes_written; ret = 1; }