starttime in /proc/$PID/stat is inaccurate by "clock tick" granularity.
The process starttime is useful for a variety of things, like figuring
out creation ordering of processes and it is useful to detect PID
reuses in a somewhat reliable way.
The kernel internally stores finer granularity values and this patch
exports them in the easily usable location /prod/$PID/status
as StartTimeMonotonic and StartTimeBootTime.
Signed-off-by: Dan Ballard <dan@xxxxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 6 +++++-
fs/proc/array.c | 8 ++++++--
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/proc.txt
b/Documentation/filesystems/proc.txt
index 22d89aa3..6ed8001 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -158,6 +158,8 @@ read the file /proc/PID/status:
TracerPid: 0 (2.4)
Uid: 501 501 501 501
Gid: 100 100 100 100
+ StartTimeMonotonic: 3766799643
+ StartTimeBootTime: 3766799643
FDSize: 256
Groups: 100 14 16
VmPeak: 5004 kB
@@ -202,7 +204,7 @@ asynchronous manner and the vaule may not be very
precise. To see a precise
snapshot of a moment, you can see /proc/<pid>/smaps file and scan page
table.
It's slow but very precise.
-Table 1-2: Contents of the status files (as of 2.6.30-rc7)
+Table 1-2: Contents of the status files (as of 3.13.0-rc3)
..............................................................................
Field Content
Name filename of the executable
@@ -215,6 +217,8 @@ Table 1-2: Contents of the status files (as of
2.6.30-rc7)
TracerPid PID of process tracing this process (0 if
not)
Uid Real, effective, saved set, and file
system UIDs
Gid Real, effective, saved set, and file
system GIDs
+ StartTimeMonotonic Start time of process in nsec from
CLOCK_MONOTONIC
+ StartTimeBootTime Start time of process in nsec from
CLOCK_BOOTTIME
FDSize number of file descriptor slots currently
allocated
Groups supplementary group list
VmPeak peak virtual memory size
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 1bd2077..34f4761 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -188,7 +188,9 @@ static inline void task_state(struct seq_file *m,
struct pid_namespace *ns,
"PPid:\t%d\n"
"TracerPid:\t%d\n"
"Uid:\t%d\t%d\t%d\t%d\n"
- "Gid:\t%d\t%d\t%d\t%d\n",
+ "Gid:\t%d\t%d\t%d\t%d\n"
+ "StartTimeMonotonic:\t%lld\n"
+ "StartTimeBootTime:\t%lld\n",
get_task_state(p),
task_tgid_nr_ns(p, ns),
task_numa_group_id(p),
@@ -201,7 +203,9 @@ static inline void task_state(struct seq_file *m,
struct pid_namespace *ns,
from_kgid_munged(user_ns, cred->gid),
from_kgid_munged(user_ns, cred->egid),
from_kgid_munged(user_ns, cred->sgid),
- from_kgid_munged(user_ns, cred->fsgid));
+ from_kgid_munged(user_ns, cred->fsgid),
+ timespec_to_ns(&p->start_time),
+ timespec_to_ns(&p->real_start_time));
task_lock(p);
if (p->files)
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
