On Fri, 04 Aug 2006 00:33:32 +0300 Ilpo Järvinen <[EMAIL PROTECTED]> wrote:
> Overflow can occur very easily with 32 bits, e.g., with 1 second > us_idle is approx. 2^20, which leaves only 11-Wlog bits for queue > length. Since the EWMA exponent is typically around 9, queue > lengths larger than 2^2 cause overflow. Whether the affected > branch is taken when us_idle is as high as 1 second, depends on > Scell_log, but with rather reasonable configuration Scell_log is > large enough to cause p->Stab to have zero index, which always > results zero shift (typically also few other small indices result > in zero shift). > > Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]> > --- > include/net/red.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/include/net/red.h b/include/net/red.h > index 5ccdbb3..1fc32e1 100644 > --- a/include/net/red.h > +++ b/include/net/red.h > @@ -212,7 +212,7 @@ static inline unsigned long red_calc_qav > * Seems, it is the best solution to > * problem of too coarse exponent tabulation. > */ > - us_idle = (p->qavg * us_idle) >> p->Scell_log; > + us_idle = (p->qavg * (long long)us_idle) >> p->Scell_log; > > if (us_idle < (p->qavg >> 1)) > return p->qavg - us_idle; Use u64 instead of long long. -- If one would give me six lines written by the hand of the most honest man, I would find something in them to have him hanged. -- Cardinal Richlieu - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
