[Crash-utility] [PATCH 3/4] remove unreachable (and slow) code
task_exists() scans known tasks for a given task address.
refresh_radix_tree_task_table() looks like:
hq_open()
for cpus {
hq_enter(per_cpu_idle_thread)
}
for ... {
hq_enter(task)
}
hq_close()
tt->running_tasks = 0
for task in retrieve_list(hq_entries) {
if (task_exists()) {
duplicate task address
continue
}
add_context()
}
Because retrieve_list returns unique tasks, the above task_exists()
check will never find a duplicate task. So remove the check. This
converts the above loop from O(N^2) to O(N) which saves considerable
startup time when there are a large number of tasks. On a 1M task dump
this patch reduces startup time: 44m => 1m.
I was not able to test the other pid table routines, but I suspect they
may also benefit from similar removal.
Signed-off-by: Greg Thelen <gthelen(a)google.com>
---
task.c | 10 ----------
1 file changed, 10 deletions(-)
diff --git a/task.c b/task.c
index 82fa015805cb..cddc1f5b651a 100644
--- a/task.c
+++ b/task.c
@@ -2473,16 +2473,6 @@ retry_radix_tree:
goto retry_radix_tree;
}
- if (task_exists(*tlp)) {
- error(WARNING,
- "%sduplicate task address found in task list: %lx\n",
- DUMPFILE() ? "\n" : "", *tlp);
- if (DUMPFILE())
- continue;
- retries++;
- goto retry_radix_tree;
- }
-
if (!(tp = fill_task_struct(*tlp))) {
if (DUMPFILE())
continue;
--
2.17.0.484.g0c8726318c-goog