tools/accounting/delaytop: add delaytop to record top-n task delay

Problem
=======

The "getdelays" can only display the latency of a single task
by specifying a PID, but it has the following limitations:

1. single-task perspective: only supports querying the latency (CPU, I/O,
memory, etc.) of an individual task via PID and cannot provide a global
analysis of high-latency processes across the system.

2. lack of High-Latency process awareness: when the overall system
   latency is high (e.g., a spike in CPU latency), there is no way to
   quickly identify the top N processes contributing to the highest
   latency.

3. poor interactivity: It lacks dynamic sorting and refresh
   capabilities (similar to top), making it difficult to monitor latency
   changes in real time.

Solution
========

To address these limitations, we introduce the "delaytop" with the
following capabilities:

1. system view: monitors latency metrics (CPU, I/O, memory, IRQ, etc.)
   for all system processes

2. supports field-based sorting (e.g., default sort by CPU latency in
   descending order)

3. dynamic interactive interface: focus on specific processes with
   --pid; limit displayed entries with --processes 20; control monitoring
   duration with --iterations;

Use case
========
bash# ./delaytop
Top 20 processes (sorted by CPU delay):

  PID   TGID  COMMAND            CPU(ms)  IO(ms)   SWAP(ms) RCL(ms) THR(ms)  CMP(ms)  WP(ms)  IRQ(ms)
---------------------------------------------------------------------------------------------
   26     26  kworker/1:0H       5.55     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   32     32  kworker/2:0H-kb    2.93     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   38     38  kworker/3:0H-ev    2.88     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   84     84  kworker/R-vfio-    1.62     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   24     24  ksoftirqd/1        1.43     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   19     19  idle_inject/0      0.99     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   16     16  rcu_exp_par_gp_    0.87     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   11     11  kworker/0:1        0.87     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   22     22  idle_inject/1      0.80     0.00     0.00     0.00    0.00     0.00     0.00     0.00
    3      3  pool_workqueue_    0.74     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   81     81  scsi_eh_1          0.59     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   30     30  ksoftirqd/2        0.42     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   36     36  ksoftirqd/3        0.37     0.00     0.00     0.00    0.00     0.00     0.00     0.00
    9      9  kworker/0:0-eve    0.36     0.00     0.00     0.00    0.00     0.00     0.00     0.00
    8      8  kworker/R-netns    0.34     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   76     76  kworker/1:1-pm     0.32     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   21     21  cpuhp/1            0.30     0.00     0.00     0.00    0.00     0.00     0.00     0.00
    4      4  kworker/R-rcu_g    0.21     0.00     0.00     0.00    0.00     0.00     0.00     0.00
   12     12  kworker/u16:0-i    0.20     0.00     0.00     0.00    0.00     0.00     0.00     0.00
    1      1  init               0.18     0.00     0.00     0.00    0.00     0.00     0.08     0.00

Link: https://lkml.kernel.org/r/[email protected]
Co-developed-by: Fan Yu <[email protected]>
Signed-off-by: Fan Yu <[email protected]>
Signed-off-by: Yaxin Wang <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Peilin He <[email protected]>
Cc: Qiang Tu <[email protected]>
Cc: wangyong <[email protected]>
Cc: xu xin <[email protected]>
Cc: Yang Yang <[email protected]>
Cc: ye xingchen <[email protected]>
Cc: Yunkai Zhang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Yaxin Wang

tools/accounting/Makefile

@@ -2,7 +2,7 @@
 CC := $(CROSS_COMPILE)gcc
 CFLAGS := -I../../usr/include
 
-PROGS := getdelays procacct
+PROGS := getdelays procacct delaytop
 
 all: $(PROGS)