On 2023/08/25 15:23, Lianbo Jiang wrote:
> When a task is exiting, usually kernel marks its flags as 'PF_EXITING',
> but even so, sometimes the mm_struct has not been freed, it might still
> be valid. For such tasks, the "ps/vm" commands won't display the memory
> usage. For example:
>
> crash> ps 47070
> PID PPID CPU TASK ST %MEM VSZ RSS COMM
> 47070 1 0 ffff9ba7c4910000 UN 0.0 0 0 ra_ris.parse
> crash> vm 47070
> PID: 47070 TASK: ffff9ba7c4910000 CPU: 0 COMMAND: "ra_ris.parse"
> MM PGD RSS TOTAL_VM
> 0 0 0k 0k
>
> To be honest, this is a corner case, but it has already occurred in
> actual production environments. Given that, let's allow the "ps/vm"
> commands to try to display the memory usage for this case, but it does
> not guarantee that it can work well at any time, which still depends on
> how far the mm_struct deconstruction has proceeded.
>
> With the patch:
> crash> ps 47070
> PID PPID CPU TASK ST %MEM VSZ RSS COMM
> 47070 1 0 ffff9ba7c4910000 UN 90.8 38461228 31426444 ra_ris.parse
> crash> vm 47070
> PID: 47070 TASK: ffff9ba7c4910000 CPU: 0 COMMAND: "ra_ris.parse"
> MM PGD RSS TOTAL_VM
> ffff9bad6e873840 ffff9baee0544000 31426444k 38461228k
> VMA START END FLAGS FILE
> ffff9bafdbe1d6c8 400000 8c5000 8000875 /data1/rishome/ra_cu_cn_412/sbin/ra_ris.parse
> ...
>
> Reported-by: Buland Kumar Singh <bsingh@xxxxxxxxxx>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> ---
> memory.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/memory.c b/memory.c
> index 5d76c5d7fe6f..86ccec5e2bac 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -4792,10 +4792,11 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
> {
> struct task_context *tc;
> long rss = 0, rss_cache = 0;
> + int mm_count = 0;
>
> BZERO(tm, sizeof(struct task_mem_usage));
>
> - if (IS_ZOMBIE(task) || IS_EXITING(task))
> + if (IS_ZOMBIE(task))
> return;
>
> tc = task_to_context(task);
> @@ -4808,6 +4809,11 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm)
> if (!task_mm(task, TRUE))
> return;
>
> + mm_count = INT(tt->mm_struct + OFFSET(mm_struct_mm_count));
> +
> + if (IS_EXITING(task) && mm_count <= 0)
> + return;
> +
> if (VALID_MEMBER(mm_struct_rss))
> /*
> * mm_struct.rss or mm_struct._rss exist.
Thanks, applied.
https://github.com/crash-utility/crash/commit/3253e5ac87c67dd7742e2b2bd9d912f21c1d2711
Kazu
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