I would like to see some performance measurements for this patch on a system with fast storage and multiple 10 GbE links.
If not, at least a good analysis of the expected performance impact the patch will have on major architectures. Tonight I will think about whether the 2038 thing even matters or whether we just need a comment explaining why it's safe. On May 11, 2015 11:38 AM, Arnd Bergmann <a...@arndb.de> wrote: > > On Monday 11 May 2015 08:05:05 Tina Ruchandani wrote: > > 'struct frame' uses two variables to store the sent timestamp - 'struct > > timeval' and jiffies. jiffies is used to avoid discrepancies caused by > > updates to system time. 'struct timeval' uses 32-bit representation for > > seconds which will overflow in year 2038. > > This patch does the following: > > - Replace the use of 'struct timeval' and jiffies with ktime_t, which > > is a 64-bit timestamp and is year 2038 safe. > > - ktime_t provides both long range (like jiffies) and high resolution > > (like timeval). Using ktime_get (monotonic time) instead of wall-clock > > time prevents any discprepancies caused by updates to system time. > > > > Signed-off-by: Tina Ruchandani <ruchandani.t...@gmail.com> > > Very nice! > > > @@ -499,32 +497,15 @@ resend(struct aoedev *d, struct frame *f) > > static int > > tsince_hr(struct frame *f) > > { > > - struct timeval now; > > + ktime_t now; > > int n; > > > > - do_gettimeofday(&now); > > - n = now.tv_usec - f->sent.tv_usec; > > - n += (now.tv_sec - f->sent.tv_sec) * USEC_PER_SEC; > > + now = ktime_get(); > > + n = ktime_to_us(ktime_sub(now, f->sent)); > > > > I would cut four extra lines by writing this as > > return ktime_us_delta(ktime_get(), f->sent)); > > but the effect is exactly the same. > > With that change, please add > > Reviewed-by: Arnd Bergmann <a...@arndb.de> > > Arnd