From bfa160b9ba27abd18f2f9bf225ea7fcfb03677f4 Mon Sep 17 00:00:00 2001
Date: Wed, 6 Oct 2021 15:17:32 -0400
Subject: [PATCH] tryfix

---
 README        |  3 ++-
 iotop.8       |  3 ++-
 iotop/data.py | 10 +++++++++-
 iotop/ui.py   | 18 ++++++++++++++----
 4 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/README b/README
index cf9e050..3f490ab 100644
--- a/README
+++ b/README
@@ -1,7 +1,8 @@
 Iotop is a Python program with a top like UI used to show of behalf of which
 process is the I/O going on. It requires Python >= 2.7 and a Linux kernel >=
 2.6.20 with the CONFIG_TASK_DELAY_ACCT CONFIG_TASKSTATS,
-CONFIG_TASK_IO_ACCOUNTING and CONFIG_VM_EVENT_COUNTERS options on.
+CONFIG_TASK_IO_ACCOUNTING and CONFIG_VM_EVENT_COUNTERS build options on
+and for Linux kernels since 5.14, the kernel.task_delayacct sysctl enabled.
 
 
 To run a local version of iotop:
diff --git a/iotop.8 b/iotop.8
index 68d9edd..e62ed3d 100644
--- a/iotop.8
+++ b/iotop.8
@@ -10,7 +10,8 @@ iotop watches I/O usage information output by the Linux kernel (requires
 2.6.20 or later) and displays a table of current I/O usage by processes
 or threads on the system. At least the CONFIG_TASK_DELAY_ACCT,
 CONFIG_TASK_IO_ACCOUNTING, CONFIG_TASKSTATS and CONFIG_VM_EVENT_COUNTERS
-options need to be enabled in your Linux kernel build configuration.
+options need to be enabled in your Linux kernel build configuration and
+since Linux kernel 5.14, the kernel.task_delayacct sysctl enabled.
 .PP
 iotop displays columns for the I/O bandwidth read and written by each
 process/thread during the sampling period. It also displays the percentage
diff --git a/iotop/data.py b/iotop/data.py
index 25b659e..e796d46 100644
--- a/iotop/data.py
+++ b/iotop/data.py
@@ -49,7 +49,7 @@ if not ioaccounting or not vm_event_counters:
     if not ioaccounting:
         print('  - I/O accounting support ' \
           '(CONFIG_TASKSTATS, CONFIG_TASK_DELAY_ACCT, ' \
-          'CONFIG_TASK_IO_ACCOUNTING)')
+          'CONFIG_TASK_IO_ACCOUNTING, kernel.task_delayacct sysctl)')
     if not vm_event_counters:
         print('  - VM event counters (CONFIG_VM_EVENT_COUNTERS)')
     sys.exit(1)
@@ -453,3 +453,11 @@ class ProcessList(DumpableObject):
 
     def clear(self):
         self.processes = {}
+
+
+def sysctl_task_delayacct():
+    try:
+        with open('/proc/sys/kernel/task_delayacct') as f:
+            return bool(int(f.read().strip()))
+    except FileNotFoundError:
+        return None
diff --git a/iotop/ui.py b/iotop/ui.py
index e033c92..9aa56ef 100644
--- a/iotop/ui.py
+++ b/iotop/ui.py
@@ -30,7 +30,7 @@ import signal
 import sys
 import time
 
-from iotop.data import find_uids, TaskStatsNetlink, ProcessList, Stats
+from iotop.data import find_uids, TaskStatsNetlink, ProcessList, Stats, sysctl_task_delayacct
 from iotop.data import ThreadInfo
 from iotop.version import VERSION
 from iotop import ioprio
@@ -377,7 +377,7 @@ class IOTopUI(object):
         def format(p):
             stats = format_stats(self.options, p, self.process_list.duration)
             io_delay, swapin_delay, read_bytes, write_bytes = stats
-            if Stats.has_blkio_delay_total:
+            if self.has_swapin_io:
                 delay_stats = '%7s %7s ' % (swapin_delay, io_delay)
             else:
                 delay_stats = ' ?unavailable?  '
@@ -431,6 +431,14 @@ class IOTopUI(object):
             pid += 'TID'
         titles = [pid, '  PRIO', '  USER', '     DISK READ', '  DISK WRITE',
                   '  SWAPIN', '      IO', '    COMMAND']
+        self.has_swapin_io = Stats.has_blkio_delay_total
+        if self.has_swapin_io:
+            # Linux kernels without the sysctl return None and
+            # iotop just uses the heuristic for those versions.
+            # Linux kernels with the sysctl return True or False
+            # and iotop then uses the sysctl value instead.
+            if sysctl_task_delayacct() == False:
+                self.has_swapin_io = False
         lines = self.get_data()
         if self.options.time:
             titles = ['    TIME'] + titles
@@ -464,10 +472,12 @@ class IOTopUI(object):
                 title = title[:remaining_cols]
                 remaining_cols -= len(title)
                 self.win.addstr(title, attr)
-            if Stats.has_blkio_delay_total:
+            if self.has_swapin_io:
                 status_msg = None
             else:
-                status_msg = ('CONFIG_TASK_DELAY_ACCT not enabled in kernel, '
+                status_msg = ('CONFIG_TASK_DELAY_ACCT '
+                              'and kernel.task_delayacct sysctl '
+                              'not enabled in kernel, '
                               'cannot determine SWAPIN and IO %')
             num_lines = min(len(lines), self.height - 2 - int(bool(status_msg)))
             for i in range(num_lines):
-- 
2.33.0