xref: /openbmc/linux/include/linux/dim.h (revision 8795a739)
1 /* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
2 /* Copyright (c) 2019 Mellanox Technologies. */
3 
4 #ifndef DIM_H
5 #define DIM_H
6 
7 #include <linux/module.h>
8 
9 /**
10  * Number of events between DIM iterations.
11  * Causes a moderation of the algorithm run.
12  */
13 #define DIM_NEVENTS 64
14 
15 /**
16  * Is a difference between values justifies taking an action.
17  * We consider 10% difference as significant.
18  */
19 #define IS_SIGNIFICANT_DIFF(val, ref) \
20 	(((100UL * abs((val) - (ref))) / (ref)) > 10)
21 
22 /**
23  * Calculate the gap between two values.
24  * Take wrap-around and variable size into consideration.
25  */
26 #define BIT_GAP(bits, end, start) ((((end) - (start)) + BIT_ULL(bits)) \
27 		& (BIT_ULL(bits) - 1))
28 
29 /**
30  * Structure for CQ moderation values.
31  * Used for communications between DIM and its consumer.
32  *
33  * @usec: CQ timer suggestion (by DIM)
34  * @pkts: CQ packet counter suggestion (by DIM)
35  * @cq_period_mode: CQ priod count mode (from CQE/EQE)
36  */
37 struct dim_cq_moder {
38 	u16 usec;
39 	u16 pkts;
40 	u16 comps;
41 	u8 cq_period_mode;
42 };
43 
44 /**
45  * Structure for DIM sample data.
46  * Used for communications between DIM and its consumer.
47  *
48  * @time: Sample timestamp
49  * @pkt_ctr: Number of packets
50  * @byte_ctr: Number of bytes
51  * @event_ctr: Number of events
52  */
53 struct dim_sample {
54 	ktime_t time;
55 	u32 pkt_ctr;
56 	u32 byte_ctr;
57 	u16 event_ctr;
58 	u32 comp_ctr;
59 };
60 
61 /**
62  * Structure for DIM stats.
63  * Used for holding current measured rates.
64  *
65  * @ppms: Packets per msec
66  * @bpms: Bytes per msec
67  * @epms: Events per msec
68  */
69 struct dim_stats {
70 	int ppms; /* packets per msec */
71 	int bpms; /* bytes per msec */
72 	int epms; /* events per msec */
73 	int cpms; /* completions per msec */
74 	int cpe_ratio; /* ratio of completions to events */
75 };
76 
77 /**
78  * Main structure for dynamic interrupt moderation (DIM).
79  * Used for holding all information about a specific DIM instance.
80  *
81  * @state: Algorithm state (see below)
82  * @prev_stats: Measured rates from previous iteration (for comparison)
83  * @start_sample: Sampled data at start of current iteration
84  * @work: Work to perform on action required
85  * @priv: A pointer to the struct that points to dim
86  * @profile_ix: Current moderation profile
87  * @mode: CQ period count mode
88  * @tune_state: Algorithm tuning state (see below)
89  * @steps_right: Number of steps taken towards higher moderation
90  * @steps_left: Number of steps taken towards lower moderation
91  * @tired: Parking depth counter
92  */
93 struct dim {
94 	u8 state;
95 	struct dim_stats prev_stats;
96 	struct dim_sample start_sample;
97 	struct dim_sample measuring_sample;
98 	struct work_struct work;
99 	void *priv;
100 	u8 profile_ix;
101 	u8 mode;
102 	u8 tune_state;
103 	u8 steps_right;
104 	u8 steps_left;
105 	u8 tired;
106 };
107 
108 /**
109  * enum dim_cq_period_mode
110  *
111  * These are the modes for CQ period count.
112  *
113  * @DIM_CQ_PERIOD_MODE_START_FROM_EQE: Start counting from EQE
114  * @DIM_CQ_PERIOD_MODE_START_FROM_CQE: Start counting from CQE (implies timer reset)
115  * @DIM_CQ_PERIOD_NUM_MODES: Number of modes
116  */
117 enum {
118 	DIM_CQ_PERIOD_MODE_START_FROM_EQE = 0x0,
119 	DIM_CQ_PERIOD_MODE_START_FROM_CQE = 0x1,
120 	DIM_CQ_PERIOD_NUM_MODES
121 };
122 
123 /**
124  * enum dim_state
125  *
126  * These are the DIM algorithm states.
127  * These will determine if the algorithm is in a valid state to start an iteration.
128  *
129  * @DIM_START_MEASURE: This is the first iteration (also after applying a new profile)
130  * @DIM_MEASURE_IN_PROGRESS: Algorithm is already in progress - check if
131  * need to perform an action
132  * @DIM_APPLY_NEW_PROFILE: DIM consumer is currently applying a profile - no need to measure
133  */
134 enum {
135 	DIM_START_MEASURE,
136 	DIM_MEASURE_IN_PROGRESS,
137 	DIM_APPLY_NEW_PROFILE,
138 };
139 
140 /**
141  * enum dim_tune_state
142  *
143  * These are the DIM algorithm tune states.
144  * These will determine which action the algorithm should perform.
145  *
146  * @DIM_PARKING_ON_TOP: Algorithm found a local top point - exit on significant difference
147  * @DIM_PARKING_TIRED: Algorithm found a deep top point - don't exit if tired > 0
148  * @DIM_GOING_RIGHT: Algorithm is currently trying higher moderation levels
149  * @DIM_GOING_LEFT: Algorithm is currently trying lower moderation levels
150  */
151 enum {
152 	DIM_PARKING_ON_TOP,
153 	DIM_PARKING_TIRED,
154 	DIM_GOING_RIGHT,
155 	DIM_GOING_LEFT,
156 };
157 
158 /**
159  * enum dim_stats_state
160  *
161  * These are the DIM algorithm statistics states.
162  * These will determine the verdict of current iteration.
163  *
164  * @DIM_STATS_WORSE: Current iteration shows worse performance than before
165  * @DIM_STATS_WORSE: Current iteration shows same performance than before
166  * @DIM_STATS_WORSE: Current iteration shows better performance than before
167  */
168 enum {
169 	DIM_STATS_WORSE,
170 	DIM_STATS_SAME,
171 	DIM_STATS_BETTER,
172 };
173 
174 /**
175  * enum dim_step_result
176  *
177  * These are the DIM algorithm step results.
178  * These describe the result of a step.
179  *
180  * @DIM_STEPPED: Performed a regular step
181  * @DIM_TOO_TIRED: Same kind of step was done multiple times - should go to
182  * tired parking
183  * @DIM_ON_EDGE: Stepped to the most left/right profile
184  */
185 enum {
186 	DIM_STEPPED,
187 	DIM_TOO_TIRED,
188 	DIM_ON_EDGE,
189 };
190 
191 /**
192  *	dim_on_top - check if current state is a good place to stop (top location)
193  *	@dim: DIM context
194  *
195  * Check if current profile is a good place to park at.
196  * This will result in reducing the DIM checks frequency as we assume we
197  * shouldn't probably change profiles, unless traffic pattern wasn't changed.
198  */
199 bool dim_on_top(struct dim *dim);
200 
201 /**
202  *	dim_turn - change profile alterning direction
203  *	@dim: DIM context
204  *
205  * Go left if we were going right and vice-versa.
206  * Do nothing if currently parking.
207  */
208 void dim_turn(struct dim *dim);
209 
210 /**
211  *	dim_park_on_top - enter a parking state on a top location
212  *	@dim: DIM context
213  *
214  * Enter parking state.
215  * Clear all movement history.
216  */
217 void dim_park_on_top(struct dim *dim);
218 
219 /**
220  *	dim_park_tired - enter a tired parking state
221  *	@dim: DIM context
222  *
223  * Enter parking state.
224  * Clear all movement history and cause DIM checks frequency to reduce.
225  */
226 void dim_park_tired(struct dim *dim);
227 
228 /**
229  *	dim_calc_stats - calculate the difference between two samples
230  *	@start: start sample
231  *	@end: end sample
232  *	@curr_stats: delta between samples
233  *
234  * Calculate the delta between two samples (in data rates).
235  * Takes into consideration counter wrap-around.
236  */
237 void dim_calc_stats(struct dim_sample *start, struct dim_sample *end,
238 		    struct dim_stats *curr_stats);
239 
240 /**
241  *	dim_update_sample - set a sample's fields with give values
242  *	@event_ctr: number of events to set
243  *	@packets: number of packets to set
244  *	@bytes: number of bytes to set
245  *	@s: DIM sample
246  */
247 static inline void
248 dim_update_sample(u16 event_ctr, u64 packets, u64 bytes, struct dim_sample *s)
249 {
250 	s->time	     = ktime_get();
251 	s->pkt_ctr   = packets;
252 	s->byte_ctr  = bytes;
253 	s->event_ctr = event_ctr;
254 }
255 
256 /**
257  *	dim_update_sample_with_comps - set a sample's fields with given
258  *	values including the completion parameter
259  *	@event_ctr: number of events to set
260  *	@packets: number of packets to set
261  *	@bytes: number of bytes to set
262  *	@comps: number of completions to set
263  *	@s: DIM sample
264  */
265 static inline void
266 dim_update_sample_with_comps(u16 event_ctr, u64 packets, u64 bytes, u64 comps,
267 			     struct dim_sample *s)
268 {
269 	dim_update_sample(event_ctr, packets, bytes, s);
270 	s->comp_ctr = comps;
271 }
272 
273 /* Net DIM */
274 
275 /**
276  *	net_dim_get_rx_moderation - provide a CQ moderation object for the given RX profile
277  *	@cq_period_mode: CQ period mode
278  *	@ix: Profile index
279  */
280 struct dim_cq_moder net_dim_get_rx_moderation(u8 cq_period_mode, int ix);
281 
282 /**
283  *	net_dim_get_def_rx_moderation - provide the default RX moderation
284  *	@cq_period_mode: CQ period mode
285  */
286 struct dim_cq_moder net_dim_get_def_rx_moderation(u8 cq_period_mode);
287 
288 /**
289  *	net_dim_get_tx_moderation - provide a CQ moderation object for the given TX profile
290  *	@cq_period_mode: CQ period mode
291  *	@ix: Profile index
292  */
293 struct dim_cq_moder net_dim_get_tx_moderation(u8 cq_period_mode, int ix);
294 
295 /**
296  *	net_dim_get_def_tx_moderation - provide the default TX moderation
297  *	@cq_period_mode: CQ period mode
298  */
299 struct dim_cq_moder net_dim_get_def_tx_moderation(u8 cq_period_mode);
300 
301 /**
302  *	net_dim - main DIM algorithm entry point
303  *	@dim: DIM instance information
304  *	@end_sample: Current data measurement
305  *
306  * Called by the consumer.
307  * This is the main logic of the algorithm, where data is processed in order to decide on next
308  * required action.
309  */
310 void net_dim(struct dim *dim, struct dim_sample end_sample);
311 
312 /* RDMA DIM */
313 
314 /*
315  * RDMA DIM profile:
316  * profile size must be of RDMA_DIM_PARAMS_NUM_PROFILES.
317  */
318 #define RDMA_DIM_PARAMS_NUM_PROFILES 9
319 #define RDMA_DIM_START_PROFILE 0
320 
321 /**
322  * rdma_dim - Runs the adaptive moderation.
323  * @dim: The moderation struct.
324  * @completions: The number of completions collected in this round.
325  *
326  * Each call to rdma_dim takes the latest amount of completions that
327  * have been collected and counts them as a new event.
328  * Once enough events have been collected the algorithm decides a new
329  * moderation level.
330  */
331 void rdma_dim(struct dim *dim, u64 completions);
332 
333 #endif /* DIM_H */
334