On Fri, Aug 31, 2012 at 01:15:09PM +0800, Tao Ma wrote:
[..]
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 1588c2d..9317d71 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -46,6 +46,8 @@ struct tg_stats_cpu {
> struct blkg_rwstat service_bytes;
> /* total IOs serviced, post merge */
> struct blkg_rwstat serviced;
> + /* total IOs queued, not submitted to the underlying device. */
> + struct blkg_rwstat io_queued;
> };
Couple of questions.
- blkg_rwstat is "unsigned" and io_queued can go negative too (Because
throttled bio can very well be dispatched from other cpu from a worker
thread). So is it a good idea to represent a negative number with
unsingned type?
- As this stat is per cpu, a reader might very well see negative (or a
huge unsigned value) as number of io_queued. Not sure if that is acceptable.
How would user space come to know whether it is a valid value or not. I
thought per cpu stats are good for continuously increasing values but
not necessarily for values which can increase as well as decrease.
Thanks
Vivek
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