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[PROF-9088] Consider timestamps in comm and fork events #366

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[PROF-9088] Consider timestamps in comm and fork events #366

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cf03668
Consider timestamps in comm and fork events
r1viollet Jan 23, 2024
b3ee9ad
Consider timestamps in fork and comm events
r1viollet Jan 24, 2024
a521115
Unwind free - Minor API change
r1viollet Jan 26, 2024
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1 change: 1 addition & 0 deletions include/dso_hdr.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,7 @@ class DsoHdr {
bool maybe_insert_erase_overlap(Dso &&dso, PerfClock::time_point timestamp);

// Clear all dsos and regions associated with this pid
bool pid_free(int pid, PerfClock::time_point timestamp);
void pid_free(int pid);

// Duplicate mapping info from parent_pid into pid
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4 changes: 3 additions & 1 deletion include/unwind.hpp
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Expand Up @@ -6,6 +6,7 @@
#pragma once

#include "ddres_def.hpp"
#include "perf_clock.hpp"

#include <sys/types.h>

Expand All @@ -27,6 +28,7 @@ DDRes unwindstate_unwind(UnwindState *us);
void unwind_cycle(UnwindState *us);

// Clear unwinding structures of this pid
void unwind_pid_free(UnwindState *us, pid_t pid);
bool unwind_pid_free(UnwindState *us, pid_t pid,
PerfClock::time_point timestamp);

} // namespace ddprof
35 changes: 22 additions & 13 deletions src/ddprof_worker.cc
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Expand Up @@ -47,7 +47,8 @@ const DDPROF_STATS s_cycled_stats[] = {
const long k_clock_ticks_per_sec = sysconf(_SC_CLK_TCK);

/// Remove all structures related to
DDRes worker_pid_free(DDProfContext &ctx, pid_t el);
DDRes worker_pid_free(DDProfContext &ctx, pid_t el,
PerfClock::time_point timestamp);

DDRes clear_unvisited_pids(DDProfContext &ctx);

Expand Down Expand Up @@ -231,7 +232,7 @@ DDRes ddprof_unwind_sample(DDProfContext &ctx, perf_event_sample *sample,
if (us->_dwfl_wrapper && us->_dwfl_wrapper->_inconsistent) {
// Loaded modules were inconsistent, assume we should flush everything.
LG_WRN("(Inconsistent DWFL/DSOs)%d - Free associated objects", us->pid);
DDRES_CHECK_FWD(worker_pid_free(ctx, us->pid));
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It weird to have to call PerfClock::now() here, perhaps having two versions of worker_pid_free (with and without timestamp) or having PerfClock::time_point::max() as default value for timestamp in worker_pid_free would be more natural.

DDRES_CHECK_FWD(worker_pid_free(ctx, us->pid, PerfClock::now()));
}
return res;
}
Expand Down Expand Up @@ -303,19 +304,21 @@ DDRes aggregate_live_allocations(DDProfContext &ctx) {
return {};
}

DDRes worker_pid_free(DDProfContext &ctx, pid_t el) {
DDRes worker_pid_free(DDProfContext &ctx, pid_t el,
PerfClock::time_point timestamp) {
DDRES_CHECK_FWD(aggregate_live_allocations_for_pid(ctx, el));
UnwindState *us = ctx.worker_ctx.us;
unwind_pid_free(us, el);
unwind_pid_free(us, el, timestamp);
ctx.worker_ctx.live_allocation.clear_pid(el);
return {};
}

DDRes clear_unvisited_pids(DDProfContext &ctx) {
UnwindState *us = ctx.worker_ctx.us;
const std::vector<pid_t> pids_remove = us->dwfl_hdr.get_unvisited();
const PerfClock::time_point now = PerfClock::now();
for (pid_t const el : pids_remove) {
DDRES_CHECK_FWD(worker_pid_free(ctx, el));
DDRES_CHECK_FWD(worker_pid_free(ctx, el, now));
}
us->dwfl_hdr.reset_unvisited();
return {};
Expand Down Expand Up @@ -584,21 +587,21 @@ void ddprof_pr_lost(DDProfContext &ctx, const perf_event_lost *lost,
}

DDRes ddprof_pr_comm(DDProfContext &ctx, const perf_event_comm *comm,
int watcher_pos) {
int watcher_pos, PerfClock::time_point timestamp) {
// Change in process name (assuming exec) : clear all associated dso
if (comm->header.misc & PERF_RECORD_MISC_COMM_EXEC) {
LG_DBG("<%d>(COMM)%d -> %s", watcher_pos, comm->pid, comm->comm);
DDRES_CHECK_FWD(worker_pid_free(ctx, comm->pid));
DDRES_CHECK_FWD(worker_pid_free(ctx, comm->pid, timestamp));
}
return {};
}

DDRes ddprof_pr_fork(DDProfContext &ctx, const perf_event_fork *frk,
int watcher_pos) {
int watcher_pos, PerfClock::time_point timestamp) {
LG_DBG("<%d>(FORK)%d -> %d/%d", watcher_pos, frk->ppid, frk->pid, frk->tid);
if (frk->ppid != frk->pid) {
// Clear everything and populate at next error or with coming samples
DDRES_CHECK_FWD(worker_pid_free(ctx, frk->pid));
DDRES_CHECK_FWD(worker_pid_free(ctx, frk->pid, timestamp));
ctx.worker_ctx.us->dso_hdr.pid_fork(frk->pid, frk->ppid);
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It would be better to only call pid_fork when pid mappings have actually been freed.

}
return {};
Expand Down Expand Up @@ -745,8 +748,11 @@ DDRes ddprof_worker_process_event(const perf_event_header *hdr, int watcher_pos,
break;
case PERF_RECORD_COMM:
if (wpid->pid) {
DDRES_CHECK_FWD(ddprof_pr_comm(
ctx, reinterpret_cast<const perf_event_comm *>(hdr), watcher_pos));
auto timestamp = perf_clock_time_point_from_timestamp(
hdr_time(hdr, watcher->sample_type));
DDRES_CHECK_FWD(
ddprof_pr_comm(ctx, reinterpret_cast<const perf_event_comm *>(hdr),
watcher_pos, timestamp));
}
break;
case PERF_RECORD_EXIT:
Expand All @@ -757,8 +763,11 @@ DDRes ddprof_worker_process_event(const perf_event_header *hdr, int watcher_pos,
break;
case PERF_RECORD_FORK:
if (wpid->pid) {
DDRES_CHECK_FWD(ddprof_pr_fork(
ctx, reinterpret_cast<const perf_event_fork *>(hdr), watcher_pos));
auto timestamp = perf_clock_time_point_from_timestamp(
hdr_time(hdr, watcher->sample_type));
DDRES_CHECK_FWD(
ddprof_pr_fork(ctx, reinterpret_cast<const perf_event_fork *>(hdr),
watcher_pos, timestamp));
}

break;
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9 changes: 9 additions & 0 deletions src/dso_hdr.cc
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Expand Up @@ -404,6 +404,15 @@ DsoHdr::DsoFindRes DsoHdr::dso_find_or_backpopulate(pid_t pid,
return dso_find_or_backpopulate(pid_mapping, pid, addr);
}

bool DsoHdr::pid_free(int pid, PerfClock::time_point timestamp) {
const auto &pid_mapping = _pid_map[pid];
if (timestamp < pid_mapping._backpopulate_state.last_backpopulate_time) {
return false;
}
pid_free(pid);
return true;
}

void DsoHdr::pid_free(int pid) { _pid_map.erase(pid); }

bool DsoHdr::pid_backpopulate(pid_t pid, int &nb_elts_added) {
Expand Down
10 changes: 8 additions & 2 deletions src/unwind.cc
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Expand Up @@ -123,11 +123,17 @@ DDRes unwindstate_unwind(UnwindState *us) {
return res;
}

void unwind_pid_free(UnwindState *us, pid_t pid) {
us->dso_hdr.pid_free(pid);
bool unwind_pid_free(UnwindState *us, pid_t pid,
PerfClock::time_point timestamp) {
if (!(us->dso_hdr.pid_free(pid, timestamp))) {
LG_DBG("(PID Free)%d -> avoid free of mappings (%ld)", pid,
timestamp.time_since_epoch().count());
return false;
}
us->dwfl_hdr.clear_pid(pid);
us->symbol_hdr.clear(pid);
us->process_hdr.clear(pid);
return true;
}

void unwind_cycle(UnwindState *us) {
Expand Down
13 changes: 13 additions & 0 deletions test/dso-ut.cc
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Expand Up @@ -160,6 +160,19 @@ TEST(DSOTest, erase) {
}
}

TEST(DSOTest, avoid_erase) {
PerfClock::init(); // init otherwise it returns 0
DsoHdr dso_hdr;
PerfClock::time_point old_now = PerfClock::now();
pid_t my_pid = getpid();
usleep(100);
int nb_elts = 0;
dso_hdr.pid_backpopulate(my_pid, nb_elts);
EXPECT_GT(nb_elts, 0);
EXPECT_FALSE(dso_hdr.pid_free(my_pid, old_now));
EXPECT_GE(dso_hdr.get_nb_dso(), nb_elts);
}

TEST(DSOTest, find_same) {
DsoHdr dso_hdr;
fill_mock_hdr(dso_hdr);
Expand Down