-----Original Message-----
> 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@xxxxxxxxxx>
Nice, it's a huge improvement in performance!
And the patch looks good to me and tested ok.
Acked-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
Thanks,
Kazu
> ---
> 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
>
> --
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