forked from Minki/linux
f4915455dc
RDMA DIM implements a different algorithm from net DIM and is based on completions which is how we can implement interrupt moderation in RDMA. The algorithm optimizes for number of completions and ratio between completions and events. In order to avoid long latencies, the implementation performs fast reduction of moderation level when the traffic changes. Signed-off-by: Yamin Friedman <yaminf@mellanox.com> Reviewed-by: Max Gurtovoy <maxg@mellanox.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
109 lines
2.6 KiB
C
109 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
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/*
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* Copyright (c) 2019, Mellanox Technologies inc. All rights reserved.
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*/
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#include <linux/dim.h>
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static int rdma_dim_step(struct dim *dim)
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{
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if (dim->tune_state == DIM_GOING_RIGHT) {
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if (dim->profile_ix == (RDMA_DIM_PARAMS_NUM_PROFILES - 1))
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return DIM_ON_EDGE;
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dim->profile_ix++;
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dim->steps_right++;
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}
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if (dim->tune_state == DIM_GOING_LEFT) {
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if (dim->profile_ix == 0)
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return DIM_ON_EDGE;
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dim->profile_ix--;
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dim->steps_left++;
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}
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return DIM_STEPPED;
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}
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static int rdma_dim_stats_compare(struct dim_stats *curr,
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struct dim_stats *prev)
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{
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/* first stat */
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if (!prev->cpms)
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return DIM_STATS_SAME;
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if (IS_SIGNIFICANT_DIFF(curr->cpms, prev->cpms))
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return (curr->cpms > prev->cpms) ? DIM_STATS_BETTER :
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DIM_STATS_WORSE;
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if (IS_SIGNIFICANT_DIFF(curr->cpe_ratio, prev->cpe_ratio))
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return (curr->cpe_ratio > prev->cpe_ratio) ? DIM_STATS_BETTER :
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DIM_STATS_WORSE;
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return DIM_STATS_SAME;
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}
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static bool rdma_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
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{
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int prev_ix = dim->profile_ix;
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u8 state = dim->tune_state;
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int stats_res;
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int step_res;
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if (state != DIM_PARKING_ON_TOP && state != DIM_PARKING_TIRED) {
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stats_res = rdma_dim_stats_compare(curr_stats,
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&dim->prev_stats);
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switch (stats_res) {
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case DIM_STATS_SAME:
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if (curr_stats->cpe_ratio <= 50 * prev_ix)
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dim->profile_ix = 0;
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break;
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case DIM_STATS_WORSE:
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dim_turn(dim);
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/* fall through */
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case DIM_STATS_BETTER:
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step_res = rdma_dim_step(dim);
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if (step_res == DIM_ON_EDGE)
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dim_turn(dim);
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break;
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}
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}
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dim->prev_stats = *curr_stats;
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return dim->profile_ix != prev_ix;
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}
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void rdma_dim(struct dim *dim, u64 completions)
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{
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struct dim_sample *curr_sample = &dim->measuring_sample;
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struct dim_stats curr_stats;
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u32 nevents;
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dim_update_sample_with_comps(curr_sample->event_ctr + 1, 0, 0,
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curr_sample->comp_ctr + completions,
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&dim->measuring_sample);
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switch (dim->state) {
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case DIM_MEASURE_IN_PROGRESS:
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nevents = curr_sample->event_ctr - dim->start_sample.event_ctr;
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if (nevents < DIM_NEVENTS)
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break;
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dim_calc_stats(&dim->start_sample, curr_sample, &curr_stats);
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if (rdma_dim_decision(&curr_stats, dim)) {
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dim->state = DIM_APPLY_NEW_PROFILE;
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schedule_work(&dim->work);
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break;
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}
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/* fall through */
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case DIM_START_MEASURE:
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dim->state = DIM_MEASURE_IN_PROGRESS;
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dim_update_sample_with_comps(curr_sample->event_ctr, 0, 0,
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curr_sample->comp_ctr,
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&dim->start_sample);
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break;
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case DIM_APPLY_NEW_PROFILE:
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break;
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}
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}
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EXPORT_SYMBOL(rdma_dim);
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