On 2025/5/23 22:11, Shakeel Butt wrote:
CC Mathieu On Fri, May 23, 2025 at 11:16:13AM +0800, Baolin Wang wrote:On some large machines with a high number of CPUs running a 64K kernel, we found that the 'RES' field is always 0 displayed by the top command for some processes, which will cause a lot of confusion for users. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 875525 root 20 0 12480 0 0 R 0.3 0.0 0:00.08 top 1 root 20 0 172800 0 0 S 0.0 0.0 0:04.52 systemd The main reason is that the batch size of the percpu counter is quite large on these machines, caching a significant percpu value, since converting mm's rss stats into percpu_counter by commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter"). Intuitively, the batch number should be optimized, but on some paths, performance may take precedence over statistical accuracy. Therefore, introducing a new interface to add the percpu statistical count and display it to users, which can remove the confusion. In addition, this change is not expected to be on a performance-critical path, so the modification should be acceptable. Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>Hi Baolin, this seems reasonale. For long term Mathieu is planning to fix this with newer hierarchical percpu counter until then this looks good.
OK. Good.
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Thanks.
