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-rw-r--r--Documentation/filesystems/proc.txt13
1 files changed, 12 insertions, 1 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 74329fd0add2..72624a16b792 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -191,6 +191,7 @@ read the file /proc/PID/status:
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
+ NoNewPrivs: 0
Seccomp: 0
voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1
@@ -262,6 +263,7 @@ Table 1-2: Contents of the status files (as of 4.1)
CapPrm bitmap of permitted capabilities
CapEff bitmap of effective capabilities
CapBnd bitmap of capabilities bounding set
+ NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
Cpus_allowed mask of CPUs on which this process may run
Cpus_allowed_list Same as previous, but in "list format"
@@ -1305,7 +1307,16 @@ second). The meanings of the columns are as follows, from left to right:
- nice: niced processes executing in user mode
- system: processes executing in kernel mode
- idle: twiddling thumbs
-- iowait: waiting for I/O to complete
+- iowait: In a word, iowait stands for waiting for I/O to complete. But there
+ are several problems:
+ 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
+ waiting for I/O to complete. When cpu goes into idle state for
+ outstanding task io, another task will be scheduled on this CPU.
+ 2. In a multi-core CPU, the task waiting for I/O to complete is not running
+ on any CPU, so the iowait of each CPU is difficult to calculate.
+ 3. The value of iowait field in /proc/stat will decrease in certain
+ conditions.
+ So, the iowait is not reliable by reading from /proc/stat.
- irq: servicing interrupts
- softirq: servicing softirqs
- steal: involuntary wait