From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, proc: report PR_SET_THP_DISABLE in proc
David Rientjes has reported that 1860033237d4 ("mm: make
PR_SET_THP_DISABLE immediately active") has changed the way how we report
THPable VMAs to the userspace. Their monitoring tool is triggering false
alarms on PR_SET_THP_DISABLE tasks because it considers an insufficient
THP usage as a memory fragmentation resp. memory pressure issue.
Before the said commit each newly created VMA inherited VM_NOHUGEPAGE flag
and that got exposed to the userspace via /proc/<pid>/smaps file. This
implementation had its downsides as explained in the commit message but it
is true that the userspace doesn't have any means to query for the process
wide THP enabled/disabled status.
PR_SET_THP_DISABLE is a process wide flag so it makes a lot of sense to
export in the process wide context rather than per-vma. Introduce a new
field to /proc/<pid>/status which export this status. If
PR_SET_THP_DISABLE is used then it reports false same as when the THP is
not compiled in. It doesn't consider the global THP status because we
already export that information via sysfs
Link: http://lkml.kernel.org/r/20181211143641.3503-4-mhocko@xxxxxxxxxx
Fixes: 1860033237d4 ("mm: make PR_SET_THP_DISABLE immediately active")
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reported-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Paul Oppenheimer <bepvte@xxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/Documentation/filesystems/proc.txt~mm-proc-report-pr_set_thp_disable-in-proc
+++ a/Documentation/filesystems/proc.txt
@@ -182,6 +182,7 @@ read the file /proc/PID/status:
VmSwap: 0 kB
HugetlbPages: 0 kB
CoreDumping: 0
+ THP_enabled: 1
Threads: 1
SigQ: 0/28578
SigPnd: 0000000000000000
@@ -256,6 +257,8 @@ Table 1-2: Contents of the status files
HugetlbPages size of hugetlb memory portions
CoreDumping process's memory is currently being dumped
(killing the process may lead to a corrupted core)
+ THP_enabled process is allowed to use THP (returns 0 when
+ PR_SET_THP_DISABLE is set on the process
Threads number of threads
SigQ number of signals queued/max. number for queue
SigPnd bitmap of pending signals for the thread
--- a/fs/proc/array.c~mm-proc-report-pr_set_thp_disable-in-proc
+++ a/fs/proc/array.c
@@ -392,6 +392,15 @@ static inline void task_core_dumping(str
seq_putc(m, '\n');
}
+static inline void task_thp_status(struct seq_file *m, struct mm_struct *mm)
+{
+ bool thp_enabled = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE);
+
+ if (thp_enabled)
+ thp_enabled = !test_bit(MMF_DISABLE_THP, &mm->flags);
+ seq_printf(m, "THP_enabled:\t%d\n", thp_enabled);
+}
+
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
@@ -406,6 +415,7 @@ int proc_pid_status(struct seq_file *m,
if (mm) {
task_mem(m, mm);
task_core_dumping(m, mm);
+ task_thp_status(m, mm);
mmput(mm);
}
task_sig(m, task);
_
