On Wed, 26 Oct 2016 10:41:28 +0800 Chao Fan <fanc.fnst@xxxxxxxxxxxxxx> wrote: > The iowait is not reliable by reading from /proc/stat, so this > method to get iowait is not suggested. And we mark it in the > document. Sorry for the delay on this. Life has been...challenging... > Signed-off-by: Cao Jin <caoj.fnst@xxxxxxxxxxxxxx> > Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx> What does this signoff chain mean? > --- > Documentation/filesystems/proc.txt | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > index 74329fd..71f5096 100644 > --- a/Documentation/filesystems/proc.txt > +++ b/Documentation/filesystems/proc.txt > @@ -1305,7 +1305,16 @@ 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 So I suppose I can apply this. But is there any chance of making it say what iowait actually measures, rather than just saying that it's unreliable? Thanks, jon -- 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
