Re: [Crash-utility] [PATCH] Improve the ps performance for vmcores with large number of threads

Previously, the ps command will iterate over all threads which have the same tgid, to accumulate their rss value, in order to get a thread/process's final rss value as part of the final output. For non-live systems, the rss accumulation values are identical for threads which have the same tgid, so there is no need to do the iteration and accumulation repeatly, thus a lot of readmem calls are skipped. Otherwise it will be the performance bottleneck if the vmcores have a large number of threads. In this patch, the rss accumulation value will be stored in a cache, next time a thread with the same tgid will take it directly without the iteration. For example, we can monitor the performance issue when a vmcore has ~65k processes, most of which are threads for several specific processes. Without the patch, it will take ~7h for ps command to finish. With the patch, ps command will finish in 1min. Signed-off-by: Tao Liu <ltao(a)redhat.com&gt;

--- defs.h | 1 + memory.c | 67 ++++++++++++++++++++++++++++++-------------------------- task.c | 1 + 3 files changed, 38 insertions(+), 31 deletions(-) diff --git a/defs.h b/defs.h index b63741c..55600d5 100644 --- a/defs.h +++ b/defs.h @@ -829,6 +829,7 @@ struct task_context { /* context stored for each task */ struct tgid_context { /* tgid and task stored for each task */ ulong tgid; ulong task; + long rss_cache; }; struct task_table { /* kernel/local task table data */ diff --git a/memory.c b/memory.c index 5af45fd..b930933 100644 --- a/memory.c +++ b/memory.c @@ -4665,7 +4665,7 @@ void get_task_mem_usage(ulong task, struct task_mem_usage *tm) { struct task_context *tc; - long rss = 0; + long rss = 0, rss_cache = 0; BZERO(tm, sizeof(struct task_mem_usage)); @@ -4730,38 +4730,43 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm) (last->tgid == (last + 1)->tgid)) last++; - while (first <= last) - { - /* count 0 -> filepages */ - if (!readmem(first->task + - OFFSET(task_struct_rss_stat) + - OFFSET(task_rss_stat_count), KVADDR, - &sync_rss, - sizeof(int), - "task_struct rss_stat MM_FILEPAGES", - RETURN_ON_ERROR)) - continue; - - rss += sync_rss; - - /* count 1 -> anonpages */ - if (!readmem(first->task + - OFFSET(task_struct_rss_stat) + - OFFSET(task_rss_stat_count) + - sizeof(int), - KVADDR, &sync_rss, - sizeof(int), - "task_struct rss_stat MM_ANONPAGES", - RETURN_ON_ERROR)) - continue; - - rss += sync_rss; - - if (first == last) - break; - first++; + /* We will use rss_cache only for dumpfile */ + if (ACTIVE() || last->rss_cache == UNINITIALIZED) { + while (first <= last) + { + /* count 0 -> filepages */ + if (!readmem(first->task + + OFFSET(task_struct_rss_stat) + + OFFSET(task_rss_stat_count), KVADDR, + &sync_rss, + sizeof(int), + "task_struct rss_stat MM_FILEPAGES", + RETURN_ON_ERROR)) + continue; + + rss_cache += sync_rss; + + /* count 1 -> anonpages */ + if (!readmem(first->task + + OFFSET(task_struct_rss_stat) + + OFFSET(task_rss_stat_count) + + sizeof(int), + KVADDR, &sync_rss, + sizeof(int), + "task_struct rss_stat MM_ANONPAGES", + RETURN_ON_ERROR)) + continue; + + rss_cache += sync_rss; + + if (first == last) + break; + first++; + } + last->rss_cache = rss_cache; } + rss += last->rss_cache; tt->last_tgid = last; } } diff --git a/task.c b/task.c index 263a834..9868a6e 100644 --- a/task.c +++ b/task.c @@ -2947,6 +2947,7 @@ add_context(ulong task, char *tp) tg = tt->tgid_array + tt->running_tasks; tg->tgid = *tgid_addr; tg->task = task; + tg->rss_cache = UNINITIALIZED; if (do_verify && !verify_task(tc, do_verify)) { error(INFO, "invalid task address: %lx\n", tc->task); -- 2.33.1 -- Crash-utility mailing list Crash-utility(a)redhat.com https://listman.redhat.com/mailman/listinfo/crash-utility