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Atoptool / atop

System and process monitor for Linux
GNU General Public License v2.0
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Correct tslpu by calculating only 'D' but not 'I' #256

Closed ShirleyFei closed 1 year ago

ShirleyFei commented 1 year ago

According to task_state_array[] from Linux kernel, "D (disk sleep)" is reported for TASK_UNINTERRUPTIBLE, and "I (idle)" is reported for TASK_IDLE[1], which composes by (TASK_UNINTERRUPTIBLE | TASK_NOLOAD). The special flag TASK_NOLOAD[2] is added for calculating idle kernel threads which do not contribute to load average like uninterruptible processes do.

Thus only TASK_UNINTERRUPTIBLE("D") is needed. Rectify this by reverting the previous patch: "Count idle threads as non-interruptible threads" as https://github.com/Atoptool/atop/commit/bb38fd80633cf11475fc18191d4cc8bf3f0e67ba

[1]https://yhbt.net/lore/all/20170925121117.224552932@infradead.org/1-peterz-sched-state-6.patch [2]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=80ed87c8a9ca0cad7ca66cf3bbdfb17559a66dcf

Atoptool commented 1 year ago

In my understanding, threads in state 'I' are still uninterruptible threads from which the sleep state can not be interrupted by a received signal and therefore it is correct that they are counted as they currently are. The fact that they won't contribute to the load average values doesn't make them interruptible. By reverting the patch, idle threads are not counted at all any more.

Atoptool commented 1 year ago

Closed by introducing separate counter.