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From:   Steve MacLean <Steve.MacLean@microsoft.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>
CC:     Eric Saint-Etienne <eric.saint.etienne@oracle.com>,
        John Keeping <john@metanate.com>,
        Andi Kleen <ak@linux.intel.com>,
        Song Liu <songliubraving@fb.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Brian Robbins <brianrob@microsoft.com>,
        Tom McDonald <Thomas.McDonald@microsoft.com>,
        John Salem <josalem@microsoft.com>,
        Stephane Eranian <eranian@google.com>
Subject: [PATCH 3/4 RESEND] perf inject --jit: Remove //anon mmap events
Thread-Topic: [PATCH 3/4 RESEND] perf inject --jit: Remove //anon mmap events
Thread-Index: AdV30UpDWyGhNX8tTHCRL/VpRSaZoA==
Date:   Mon, 30 Sep 2019 21:00:01 +0000
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While a JIT is jitting code it will eventually need to commit more pages an=
d
change these pages to executable permissions.

Typically the JIT will want these collocated to minimize branch displacemen=
ts.

The kernel will coalesce these anonymous mapping with identical permissions
before sending an mmap event for the new pages. This means the mmap event f=
or
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file represents inferior information which has been superseded by the
jitdump jit-xxx.dump file.

Further the '//anon*' mmap events are only required for the legacy
perf-xxx.map mapping.

Summary:

Add rbtree to track which pids have successfully injected a jitdump file.

During "perf inject --jit", discard "//anon*" mmap events for any pid which
has successfully processed a jitdump file.

Committer testing:

// jitdump case
perf record <app with jitdump>
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 <app without jitdump>
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.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Steve MacLean <Steve.MacLean@Microsoft.com>
---
tools/perf/builtin-inject.c |  4 +--
 tools/perf/util/jitdump.c   | 63 +++++++++++++++++++++++++++++++++++++++++=
++++
 2 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index c14f40b8..4c921e0 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -261,7 +261,7 @@ static int perf_event__jit_repipe_mmap(struct perf_tool=
 *tool,
         * if jit marker, then inject jit mmaps and generate ELF images
         */
        ret =3D 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) {
@@ -299,7 +299,7 @@ static int perf_event__jit_repipe_mmap2(struct perf_too=
l *tool,
         * if jit marker, then inject jit mmaps and generate ELF images
         */
        ret =3D 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 22d09c4..6a1563f 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -751,6 +751,59 @@ jit_detect(char *mmap_name, pid_t pid)
        return 0;
 }
=20
+struct pid_rbtree
+{
+       struct rb_node node;
+       pid_t pid;
+};
+
+static void jit_add_pid(struct rb_root *root, pid_t pid)
+{
+       struct rb_node **new =3D &(root->rb_node), *parent =3D NULL;
+       struct pid_rbtree* data =3D NULL;
+
+       /* Figure out where to put new node */
+       while (*new) {
+               struct pid_rbtree *this =3D container_of(*new, struct pid_r=
btree, node);
+               pid_t nodePid =3D this->pid;
+
+               parent =3D *new;
+               if (pid < nodePid)
+                       new =3D &((*new)->rb_left);
+               else if (pid > nodePid)
+                       new =3D &((*new)->rb_right);
+               else
+                       return;
+       }
+
+       data =3D malloc(sizeof(struct pid_rbtree));
+       data->pid =3D pid;
+
+       /* Add new node and rebalance tree. */
+       rb_link_node(&data->node, parent, new);
+       rb_insert_color(&data->node, root);
+
+       return;
+}
+
+static bool jit_has_pid(struct rb_root *root, pid_t pid)
+{
+       struct rb_node *node =3D root->rb_node;
+
+       while (node) {
+               struct pid_rbtree *this =3D container_of(node, struct pid_r=
btree, node);
+               pid_t nodePid =3D this->pid;
+
+               if (pid < nodePid)
+                       node =3D node->rb_left;
+               else if (pid > nodePid)
+                       node =3D node->rb_right;
+               else
+                       return 1;
+       }
+       return 0;
+}
+
 int
 jit_process(struct perf_session *session,
            struct perf_data *output,
@@ -762,12 +815,21 @@ jit_process(struct perf_session *session,
        struct evsel *first;
        struct jit_buf_desc jd;
        int ret;
+       static struct rb_root jitdump_pids =3D RB_ROOT;
=20
        /*
         * first, detect marker mmap (i.e., the jitdump mmap)
         */
        if (jit_detect(filename, pid))
+       {
+               /*
+                * Strip //anon* mmaps if we processed a jitdump for this p=
id
+                */
+               if (jit_has_pid(&jitdump_pids, pid) && (strncmp(filename, "=
//anon", 6) =3D=3D 0))
+                       return 1;
+
                return 0;
+       }
=20
        memset(&jd, 0, sizeof(jd));
=20
@@ -786,6 +848,7 @@ jit_process(struct perf_session *session,
=20
        ret =3D jit_inject(&jd, filename);
        if (!ret) {
+               jit_add_pid(&jitdump_pids, pid);
                *nbytes =3D jd.bytes_written;
                ret =3D 1;
        }
--=20
2.7.4