diff options
Diffstat (limited to 'net/dccp/ccids/lib/tfrc.h')
| -rw-r--r-- | net/dccp/ccids/lib/tfrc.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h index bb47146ac7d..ede12f53de5 100644 --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -48,6 +48,21 @@ static inline u32 scaled_div32(u64 a, u64 b) } /** + * tfrc_scaled_sqrt - Compute scaled integer sqrt(x) for 0 < x < 2^22-1 + * Uses scaling to improve accuracy of the integer approximation of sqrt(). The + * scaling factor of 2^10 limits the maximum @sample to 4e6; this is okay for + * clamped RTT samples (dccp_sample_rtt). + * Should best be used for expressions of type sqrt(x)/sqrt(y), since then the + * scaling factor is neutralised. For this purpose, it avoids returning zero. + */ +static inline u16 tfrc_scaled_sqrt(const u32 sample) +{ + const unsigned long non_zero_sample = sample ? : 1; + + return int_sqrt(non_zero_sample << 10); +} + +/** * tfrc_ewma - Exponentially weighted moving average * @weight: Weight to be used as damping factor, in units of 1/10 */ |