Re: [PATCH 0/3] delaytop: add delay max, timestamp and sorting for top latency analysis

[wang.yaxin]

>> From: Wang Yaxin <wang.yaxin@xxxxxxxxxx>
>> 
>> Previously delaytop only showed average delays. This patch adds:
>> 
>> 1. delay_max fields to track the maximum delay value for each delay type
>>    (cpu, blkio, irq, swapin, freepages, thrashing, compact, wpcopy)
>>    per task.
>> 
>> 2. The -t/--type option displays only the specified delay type with avg/max
>>    values side by side, allowing focused analysis:
>>      delaytop -t cpu    # Show only CPU delay with avg/max
>>      delaytop -t wpcopy # Show Copy-on-Write delay with avg/max
>> 
>> 3. Wall-clock timestamp when each maximum delay occurred, displayed in the
>>    MAX_TIMESTAMP column when using -t/--type option. This enables:
>>    - Identifying the time when a process experienced an abnormal delay max
>>    - Correlating delay max across multiple processes at the same timestamp
>>    - Cross-referencing with logs, traces, or other metrics at that time
>> 
>> 4. When using -t/--type option, tasks are sorted by maximum delay value in
>>    descending order (largest delay first), enabling quick identification of
>>    top N processes with highest delay spikes.
>
>Sounds useful.  Am I correct in assuming that you're a regular user of
>delaytop and that these changes are based on your experience with it?

This indeed comes from latency observation requirements in business
scenarios. Some of our tasks are highly latency-sensitive, so we
need to monitor the "delay max" of specific tasks and detect anomalies
in a timely manner. delaytop is very useful for observing task-level
latency.

Thanks for the review. I will submit the v2 patch to fix the potential
issues as suggested

Thanks
Yaxin