rc80211-pid: add debugging

This adds a new debugfs file from which rate control relevant events can be
read one event per line. The output includes the current time, so graphs can be
created showing the rate control parameters. This helps in evaluating and
tuning rate control parameters. While at it, we split headers and code for
better readability.

Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de>
Signed-off-by: Stefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 242 insertions, 0 deletions

diff --git a/net/mac80211/rc80211_pid.h b/net/mac80211/rc80211_pid.h
new file mode 100644
index 00000000000..5d0056c1513
--- /dev/null
+++ b/net/mac80211/rc80211_pid.h
@@ -0,0 +1,242 @@
+/*
+ * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef RC80211_PID_H
+#define RC80211_PID_H
+
+/* Sampling period for measuring percentage of failed frames. */
+#define RC_PID_INTERVAL (HZ / 8)
+
+/* Exponential averaging smoothness (used for I part of PID controller) */
+#define RC_PID_SMOOTHING_SHIFT 3
+#define RC_PID_SMOOTHING (1 << RC_PID_SMOOTHING_SHIFT)
+
+/* Sharpening factor (used for D part of PID controller) */
+#define RC_PID_SHARPENING_FACTOR 0
+#define RC_PID_SHARPENING_DURATION 0
+
+/* Fixed point arithmetic shifting amount. */
+#define RC_PID_ARITH_SHIFT 8
+
+/* Fixed point arithmetic factor. */
+#define RC_PID_ARITH_FACTOR (1 << RC_PID_ARITH_SHIFT)
+
+/* Proportional PID component coefficient. */
+#define RC_PID_COEFF_P 15
+/* Integral PID component coefficient. */
+#define RC_PID_COEFF_I 9
+/* Derivative PID component coefficient. */
+#define RC_PID_COEFF_D 15
+
+/* Target failed frames rate for the PID controller. NB: This effectively gives
+ * maximum failed frames percentage we're willing to accept. If the wireless
+ * link quality is good, the controller will fail to adjust failed frames
+ * percentage to the target. This is intentional.
+ */
+#define RC_PID_TARGET_PF (11 << RC_PID_ARITH_SHIFT)
+
+/* Rate behaviour normalization quantity over time. */
+#define RC_PID_NORM_OFFSET 3
+
+/* Push high rates right after loading. */
+#define RC_PID_FAST_START 0
+
+/* Arithmetic right shift for positive and negative values for ISO C. */
+#define RC_PID_DO_ARITH_RIGHT_SHIFT(x, y) \
+        (x) < 0 ? -((-(x)) >> (y)) : (x) >> (y)
+
+enum rc_pid_event_type {
+        RC_PID_EVENT_TYPE_TX_STATUS,
+        RC_PID_EVENT_TYPE_RATE_CHANGE,
+        RC_PID_EVENT_TYPE_TX_RATE,
+        RC_PID_EVENT_TYPE_PF_SAMPLE,
+};
+
+union rc_pid_event_data {
+        /* RC_PID_EVENT_TX_STATUS */
+        struct {
+                struct ieee80211_tx_status tx_status;
+        };
+        /* RC_PID_EVENT_TYPE_RATE_CHANGE */
+        /* RC_PID_EVENT_TYPE_TX_RATE */
+        struct {
+                int index;
+                int rate;
+        };
+        /* RC_PID_EVENT_TYPE_PF_SAMPLE */
+        struct {
+                s32 pf_sample;
+                s32 prop_err;
+                s32 int_err;
+                s32 der_err;
+        };
+};
+
+struct rc_pid_event {
+        /* The time when the event occured */
+        unsigned long timestamp;
+
+        /* Event ID number */
+        unsigned int id;
+
+        /* Type of event */
+        enum rc_pid_event_type type;
+
+        /* type specific data */
+        union rc_pid_event_data data;
+};
+
+/* Size of the event ring buffer. */
+#define RC_PID_EVENT_RING_SIZE 32
+
+struct rc_pid_event_buffer {
+        /* Counter that generates event IDs */
+        unsigned int ev_count;
+
+        /* Ring buffer of events */
+        struct rc_pid_event ring[RC_PID_EVENT_RING_SIZE];
+
+        /* Index to the entry in events_buf to be reused */
+        unsigned int next_entry;
+
+        /* Lock that guards against concurrent access to this buffer struct */
+        spinlock_t lock;
+
+        /* Wait queue for poll/select and blocking I/O */
+        wait_queue_head_t waitqueue;
+};
+
+struct rc_pid_events_file_info {
+        /* The event buffer we read */
+        struct rc_pid_event_buffer *events;
+
+        /* The entry we have should read next */
+        unsigned int next_entry;
+};
+
+void rate_control_pid_event_tx_status(struct rc_pid_event_buffer *buf,
+                                             struct ieee80211_tx_status *stat);
+
+void rate_control_pid_event_rate_change(struct rc_pid_event_buffer *buf,
+                                               int index, int rate);
+
+void rate_control_pid_event_tx_rate(struct rc_pid_event_buffer *buf,
+                                           int index, int rate);
+
+void rate_control_pid_event_pf_sample(struct rc_pid_event_buffer *buf,
+                                             s32 pf_sample, s32 prop_err,
+                                             s32 int_err, s32 der_err);
+
+void rate_control_pid_add_sta_debugfs(void *priv, void *priv_sta,
+                                             struct dentry *dir);
+
+void rate_control_pid_remove_sta_debugfs(void *priv, void *priv_sta);
+
+struct rc_pid_sta_info {
+        unsigned long last_change;
+        unsigned long last_sample;
+
+        u32 tx_num_failed;
+        u32 tx_num_xmit;
+
+        /* Average failed frames percentage error (i.e. actual vs. target
+         * percentage), scaled by RC_PID_SMOOTHING. This value is computed
+         * using using an exponential weighted average technique:
+         *
+         *           (RC_PID_SMOOTHING - 1) * err_avg_old + err
+         * err_avg = ------------------------------------------
+         *                       RC_PID_SMOOTHING
+         *
+         * where err_avg is the new approximation, err_avg_old the previous one
+         * and err is the error w.r.t. to the current failed frames percentage
+         * sample. Note that the bigger RC_PID_SMOOTHING the more weight is
+         * given to the previous estimate, resulting in smoother behavior (i.e.
+         * corresponding to a longer integration window).
+         *
+         * For computation, we actually don't use the above formula, but this
+         * one:
+         *
+         * err_avg_scaled = err_avg_old_scaled - err_avg_old + err
+         *
+         * where:
+         *      err_avg_scaled = err * RC_PID_SMOOTHING
+         *      err_avg_old_scaled = err_avg_old * RC_PID_SMOOTHING
+         *
+         * This avoids floating point numbers and the per_failed_old value can
+         * easily be obtained by shifting per_failed_old_scaled right by
+         * RC_PID_SMOOTHING_SHIFT.
+         */
+        s32 err_avg_sc;
+
+        /* Last framed failes percentage sample. */
+        u32 last_pf;
+
+        /* Sharpening needed. */
+        u8 sharp_cnt;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+        /* Event buffer */
+        struct rc_pid_event_buffer events;
+
+        /* Events debugfs file entry */
+        struct dentry *events_entry;
+#endif
+};
+
+/* Algorithm parameters. We keep them on a per-algorithm approach, so they can
+ * be tuned individually for each interface.
+ */
+struct rc_pid_rateinfo {
+
+        /* Map sorted rates to rates in ieee80211_hw_mode. */
+        int index;
+
+        /* Map rates in ieee80211_hw_mode to sorted rates. */
+        int rev_index;
+
+        /* Did we do any measurement on this rate? */
+        bool valid;
+
+        /* Comparison with the lowest rate. */
+        int diff;
+};
+
+struct rc_pid_info {
+
+        /* The failed frames percentage target. */
+        unsigned int target;
+
+        /* Rate at which failed frames percentage is sampled in 0.001s. */
+        unsigned int sampling_period;
+
+        /* P, I and D coefficients. */
+        int coeff_p;
+        int coeff_i;
+        int coeff_d;
+
+        /* Exponential averaging shift. */
+        unsigned int smoothing_shift;
+
+        /* Sharpening shift and duration. */
+        unsigned int sharpen_shift;
+        unsigned int sharpen_duration;
+
+        /* Normalization offset. */
+        unsigned int norm_offset;
+
+        /* Fast starst parameter. */
+        unsigned int fast_start;
+
+        /* Rates information. */
+        struct rc_pid_rateinfo *rinfo;
+
+        /* Index of the last used rate. */
+        int oldrate;
+};
+
+#endif /* RC80211_PID_H */