linux-toradex.git/kernel/delayacct.c, branch v7.0-rc6

delayacct: fix uapi timespec64 definition

2026-02-08T08:13:32+00:00

The custom definition of 'struct timespec64' is incompatible with both the
kernel's internal definition and the glibc type, at least on big-endian
targets that have the tv_nsec field in a different place, and the
definition clashes with any userspace that also defines a timespec64
structure.

Running the header check with -Wpadding enabled produces this output that
warns about the incorrect padding:

usr/include/linux/taskstats.h:25:1: error: padding struct size to alignment boundary with 4 bytes [-Werror=padded]

Remove the hack and instead use the regular __kernel_timespec type that is
meant to be used in uapi definitions.

Link: https://lkml.kernel.org/r/20260202095906.1344100-1-arnd@kernel.org
Fixes: 29b63f6eff0e ("delayacct: add timestamp of delay max")
Signed-off-by: Arnd Bergmann 
Cc: Fan Yu 
Cc: Jonathan Corbet 
Cc: xu xin 
Cc: Yang Yang 
Cc: Balbir Singh 
Cc: Jiang Kun 
Signed-off-by: Andrew Morton

delayacct: add timestamp of delay max

2026-02-01T00:16:06+00:00

Problem
=======
Commit 658eb5ab916d ("delayacct: add delay max to record delay peak")
introduced the delay max for getdelays, which records abnormal latency
peaks and helps us understand the magnitude of such delays.  However, the
peak latency value alone is insufficient for effective root cause
analysis.  Without the precise timestamp of when the peak occurred, we
still lack the critical context needed to correlate it with other system
events.

Solution
========
To address this, we need to additionally record a precise timestamp when
the maximum latency occurs.  By correlating this timestamp with system
logs and monitoring metrics, we can identify processes with abnormal
resource usage at the same moment, which can help us to pinpoint root
causes.

Use Case
========
bash-4.4# ./getdelays -d -t 227
print delayacct stats ON
TGID    227
CPU         count     real total  virtual total    delay total  delay average      delay max      delay min      delay max timestamp
               46      188000000      192348334        4098012          0.089ms     0.429260ms     0.051205ms    2026-01-15T15:06:58
IO          count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A
SWAP        count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A
RECLAIM     count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A
THRAS HING   count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A
COMPACT     count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A
WPCOPY      count    delay total  delay average      delay max      delay min      delay max timestamp
              182       19413338          0.107ms     0.547353ms     0.022462ms    2026-01-15T15:05:24
IRQ         count    delay total  delay average      delay max      delay min      delay max timestamp
                0              0          0.000ms     0.000000ms     0.000000ms                    N/A

Link: https://lkml.kernel.org/r/20260119100241520gWubW8-5QfhSf9gjqcc_E@zte.com.cn
Signed-off-by: Wang Yaxin 
Cc: Fan Yu 
Cc: Jonathan Corbet 
Cc: xu xin 
Cc: Yang Yang 
Signed-off-by: Andrew Morton

delayacct: remove redundant code and adjust indentation

2025-05-28T02:40:33+00:00

Remove redundant code and adjust indentation of xxx_delay_max/min.

Link: https://lkml.kernel.org/r/20250521093157668iQrhhcMjA-th5LQf4-A3c@zte.com.cn
Signed-off-by: Wang Yaxin 
Signed-off-by: Jiang Kun 
Cc: Balbir Singh 
Cc: xu xin 
Cc: Yang Yang 
Signed-off-by: Andrew Morton

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37+00:00

Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.

Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.

Created this by running an spatch followed by a sed command:
Spatch:
    virtual patch

    @
    depends on !(file in "net")
    disable optional_qualifier
    @

    identifier table_name != {
      watchdog_hardlockup_sysctl,
      iwcm_ctl_table,
      ucma_ctl_table,
      memory_allocation_profiling_sysctls,
      loadpin_sysctl_table
    };
    @@

    + const
    struct ctl_table table_name [] = { ... };

sed:
    sed --in-place \
      -e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
      kernel/utsname_sysctl.c

Reviewed-by: Song Liu 
Acked-by: Steven Rostedt (Google)  # for kernel/trace/
Reviewed-by: Martin K. Petersen  # SCSI
Reviewed-by: Darrick J. Wong  # xfs
Acked-by: Jani Nikula 
Acked-by: Corey Minyard 
Acked-by: Wei Liu 
Acked-by: Thomas Gleixner 
Reviewed-by: Bill O'Donnell 
Acked-by: Baoquan He 
Acked-by: Ashutosh Dixit 
Acked-by: Anna Schumaker 
Signed-off-by: Joel Granados

delayacct: add delay min to record delay peak

2025-01-13T04:21:16+00:00

Delay accounting can now calculate the average delay of processes, detect
the overall system load, and also record the 'delay max' to identify
potential abnormal delays.  However, 'delay min' can help us identify
another useful delay peak.  By comparing the difference between 'delay
max' and 'delay min', we can understand the optimization space for
latency, providing a reference for the optimization of latency
performance.

Use case
=========
bash-4.4# ./getdelays -d -t 242
print delayacct stats ON
TGID    242
CPU         count     real total  virtual total    delay total  delay average      delay max      delay min
               39      156000000      156576579        2111069          0.054ms     0.212296ms     0.031307ms
IO          count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms
SWAP        count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms
RECLAIM     count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms
THRASHING   count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms
COMPACT     count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms
WPCOPY      count    delay total  delay average      delay max      delay min
              156       11215873          0.072ms     0.207403ms     0.033913ms
IRQ         count    delay total  delay average      delay max      delay min
                0              0          0.000ms     0.000000ms     0.000000ms

Link: https://lkml.kernel.org/r/20241220173105906EOdsPhzjMLYNJJBqgz1ga@zte.com.cn
Co-developed-by: Wang Yong 
Signed-off-by: Wang Yong 
Co-developed-by: xu xin 
Signed-off-by: xu xin 
Signed-off-by: Wang Yaxin 
Co-developed-by: Kun Jiang 
Signed-off-by: Kun Jiang 
Cc: Balbir Singh 
Cc: David Hildenbrand 
Cc: Fan Yu 
Cc: Peilin He 
Cc: tuqiang 
Cc: ye xingchen 
Cc: Yunkai Zhang 
Signed-off-by: Andrew Morton

delayacct: add delay max to record delay peak

2025-01-13T04:20:59+00:00

Introduce the use cases of delay max, which can help quickly detect
potential abnormal delays in the system and record the types and specific
details of delay spikes.

Problem
========
Delay accounting can track the average delay of processes to show
system workload. However, when a process experiences a significant
delay, maybe a delay spike, which adversely affects performance,
getdelays can only display the average system delay over a period
of time. Yet, average delay is unhelpful for diagnosing delay peak.
It is not even possible to determine which type of delay has spiked,
as this information might be masked by the average delay.

Solution
=========
the 'delay max' can display delay peak since the system's startup,
which can record potential abnormal delays over time, including
the type of delay and the maximum delay. This is helpful for
quickly identifying crash caused by delay.

Use case
=========
bash# ./getdelays -d -p 244
print delayacct stats ON
PID     244

CPU             count     real total  virtual total    delay total  delay average      delay max
                   68      192000000      213676651         705643          0.010ms     0.306381ms
IO              count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms
SWAP            count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms
RECLAIM         count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms
THRASHING       count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms
COMPACT         count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms
WPCOPY          count    delay total  delay average      delay max
                  235       15648284          0.067ms     0.263842ms
IRQ             count    delay total  delay average      delay max
                    0              0          0.000ms     0.000000ms

[wang.yaxin@zte.com.cn: update docs and fix some spelling errors]
  Link: https://lkml.kernel.org/r/20241213192700771XKZ8H30OtHSeziGqRVMs0@zte.com.cn
Link: https://lkml.kernel.org/r/20241203164848805CS62CQPQWG9GLdQj2_BxS@zte.com.cn
Co-developed-by: Wang Yong 
Signed-off-by: Wang Yong 
Co-developed-by: xu xin 
Signed-off-by: xu xin 
Co-developed-by: Wang Yaxin 
Signed-off-by: Wang Yaxin 
Signed-off-by: Kun Jiang 
Cc: Balbir Singh 
Cc: David Hildenbrand 
Cc: Fan Yu 
Cc: Peilin He 
Cc: tuqiang 
Cc: Yang Yang 
Cc: ye xingchen 
Cc: Yunkai Zhang 
Signed-off-by: Andrew Morton

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh 
Signed-off-by: Thomas Weißschuh 
Co-developed-by: Joel Granados 
Signed-off-by: Joel Granados

delayacct: Remove the now superfluous sentinel elements from ctl_table array

2024-04-24T07:43:54+00:00

This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Remove sentinel element from kern_delayacct_table

Signed-off-by: Joel Granados

delayacct: track delays from IRQ/SOFTIRQ

2023-04-18T23:39:34+00:00

Delay accounting does not track the delay of IRQ/SOFTIRQ.  While
IRQ/SOFTIRQ could have obvious impact on some workloads productivity, such
as when workloads are running on system which is busy handling network
IRQ/SOFTIRQ.

Get the delay of IRQ/SOFTIRQ could help users to reduce such delay.  Such
as setting interrupt affinity or task affinity, using kernel thread for
NAPI etc.  This is inspired by "sched/psi: Add PSI_IRQ to track
IRQ/SOFTIRQ pressure"[1].  Also fix some code indent problems of older
code.

And update tools/accounting/getdelays.c:
    / # ./getdelays -p 156 -di
    print delayacct stats ON
    printing IO accounting
    PID     156

    CPU             count     real total  virtual total    delay total  delay average
                       15       15836008       16218149      275700790         18.380ms
    IO              count    delay total  delay average
                        0              0          0.000ms
    SWAP            count    delay total  delay average
                        0              0          0.000ms
    RECLAIM         count    delay total  delay average
                        0              0          0.000ms
    THRASHING       count    delay total  delay average
                        0              0          0.000ms
    COMPACT         count    delay total  delay average
                        0              0          0.000ms
    WPCOPY          count    delay total  delay average
                       36        7586118          0.211ms
    IRQ             count    delay total  delay average
                       42         929161          0.022ms

[1] commit 52b1364ba0b1("sched/psi: Add PSI_IRQ to track IRQ/SOFTIRQ pressure")

Link: https://lkml.kernel.org/r/202304081728353557233@zte.com.cn
Signed-off-by: Yang Yang 
Cc: Jiang Xuexin 
Cc: wangyong 
Cc: junhua huang 
Cc: Balbir Singh 
Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Juri Lelli 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton

delayacct: support re-entrance detection of thrashing accounting

2022-09-27T02:46:07+00:00

Once upon a time, we only support accounting thrashing of page cache. 
Then Joonsoo introduced workingset detection for anonymous pages and we
gained the ability to account thrashing of them[1].

For page cache thrashing accounting, there is no suitable place to do it
in fs level likes swap_readpage().  So we have to do it in
folio_wait_bit_common().

Then for anonymous pages thrashing accounting, we have to do it in both
swap_readpage() and folio_wait_bit_common().  This likes PSI, so we should
let thrashing accounting supports re-entrance detection.

This patch is to prepare complete thrashing accounting, and is based on
patch "filemap: make the accounting of thrashing more consistent".

[1] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")

Link: https://lkml.kernel.org/r/20220815071134.74551-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang 
Signed-off-by: CGEL ZTE 
Reviewed-by: Ran Xiaokai 
Reviewed-by: wangyong 
Acked-by: Joonsoo Kim 
Signed-off-by: Andrew Morton