a4f1f9ac81
This commit introduces a generic library to estimate either the min or max value of a time-varying variable over a recent time window. This is code originally from Kathleen Nichols. The current form of the code is from Van Jacobson. A single struct minmax_sample will track the estimated windowed-max value of the series if you call minmax_running_max() or the estimated windowed-min value of the series if you call minmax_running_min(). Nearly equivalent code is already in place for minimum RTT estimation in the TCP stack. This commit extracts that code and generalizes it to handle both min and max. Moving the code here reduces the footprint and complexity of the TCP code base and makes the filter generally available for other parts of the codebase, including an upcoming TCP congestion control module. This library works well for time series where the measurements are smoothly increasing or decreasing. Signed-off-by: Van Jacobson <vanj@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
38 lines
793 B
C
38 lines
793 B
C
/**
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* lib/minmax.c: windowed min/max tracker by Kathleen Nichols.
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*
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*/
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#ifndef MINMAX_H
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#define MINMAX_H
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#include <linux/types.h>
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/* A single data point for our parameterized min-max tracker */
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struct minmax_sample {
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u32 t; /* time measurement was taken */
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u32 v; /* value measured */
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};
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/* State for the parameterized min-max tracker */
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struct minmax {
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struct minmax_sample s[3];
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};
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static inline u32 minmax_get(const struct minmax *m)
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{
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return m->s[0].v;
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}
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static inline u32 minmax_reset(struct minmax *m, u32 t, u32 meas)
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{
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struct minmax_sample val = { .t = t, .v = meas };
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m->s[2] = m->s[1] = m->s[0] = val;
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return m->s[0].v;
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}
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u32 minmax_running_max(struct minmax *m, u32 win, u32 t, u32 meas);
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u32 minmax_running_min(struct minmax *m, u32 win, u32 t, u32 meas);
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#endif
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