On Fri, May 23, 2014 at 01:39:57PM -0400, Tejun Heo wrote:
> Hello, Vivek.
>
> On Wed, Apr 23, 2014 at 03:21:09PM -0400, Vivek Goyal wrote:
> > What about sync/async differentiation? Throttling layer seems to flag a
> > request sync
> > only if bio->bi_rw flag has REQ_SYNC set. While CFQ seems to consider
> > request sync if bio is either read or bio->bi_rw has REQ_SYNC flag set.
>
> Working on this again, AFAICS, both treat REQ_SYNC the same way as far
> as stats are concerned. If SYNC is set, it's sync; otherwise, it's
> accounted as async whether read or write.
Ok, that seems to be the case.
static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
int rw, uint64_t val)
{
u64_stats_update_begin(&rwstat->syncp);
if (rw & REQ_SYNC)
rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
else
rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
u64_stats_update_end(&rwstat->syncp);
}
So sync will represent not policy specific interpretation of sync but
based on sync flag on request.
I guess it is fine. So far nobody seems to be complaining.
Thanks
Vivek
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