Date:   Sun,  3 Feb 2019 15:50:39 +0200
From:   Tal Gilboa <talgi@...lanox.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Tariq Toukan <tariqt@...lanox.com>,
        Tal Gilboa <talgi@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Idan Burstein <idanb@...lanox.com>,
        Yamin Friedman <yaminf@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andy Gospodarek <andrew.gospodarek@...adcom.com>
Subject: [RFC/PATCH net-next 8/9] linux/dim: Implement blk_dim.h

From: Yamin Friedman <yaminf@...lanox.com>

blk_dim implements a different algorithm than net_dim that is optimized for nvmf
storage applications.
The algorithm optimizes for number of completions and ratio between completions
and events.
It also has a feature for fast reduction of moderation level when the traffic
changes in such a way as to no longer require high moderation in order to avoid
long latencies.

blk_dim.h will be called from the ib_core module.

Signed-off-by: Yamin Friedman <yaminf@...lanox.com>
Signed-off-by: Tal Gilboa <talgi@...lanox.com>
---
 MAINTAINERS             |   1 +
 include/linux/blk_dim.h |  56 ++++++++++++++++++++
 lib/dim/Makefile        |   7 ++-
 lib/dim/blk_dim.c       | 114 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 177 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/blk_dim.h
 create mode 100644 lib/dim/blk_dim.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 6ae949be8b83..2860a3316be5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5337,6 +5337,7 @@ DYNAMIC INTERRUPT MODERATION
 M:	Tal Gilboa <talgi@...lanox.com>
 S:	Maintained
 F:	include/linux/net_dim.h
+F:	include/linux/blk_dim.h
 F:	include/linux/dim.h
 F:	lib/dim/
 
diff --git a/include/linux/blk_dim.h b/include/linux/blk_dim.h
new file mode 100644
index 000000000000..a044f62ec8fe
--- /dev/null
+++ b/include/linux/blk_dim.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016, Mellanox Technologies. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef BLK_DIM_H
+#define BLK_DIM_H
+
+#include <linux/module.h>
+#include <linux/dim.h>
+
+#define BLK_DIM_PARAMS_NUM_PROFILES 8
+#define BLK_DIM_START_PROFILE 0
+
+static const struct dim_cq_moder
+blk_dim_prof[BLK_DIM_PARAMS_NUM_PROFILES] = {
+	{1,   0, 1,  0},
+	{2,   0, 2,  0},
+	{4,   0, 4,  0},
+	{16,  0, 4,  0},
+	{32,  0, 4,  0},
+	{32,  0, 16, 0},
+	{256, 0, 16, 0},
+	{256, 0, 32, 0},
+};
+
+void blk_dim(struct dim *dim, struct dim_sample end_sample);
+
+#endif /* BLK_DIM_H */
diff --git a/lib/dim/Makefile b/lib/dim/Makefile
index 160afe288df0..2b3c57318dbb 100644
--- a/lib/dim/Makefile
+++ b/lib/dim/Makefile
@@ -2,8 +2,13 @@
 # DIM Dynamic Interrupt Moderation library
 #
 
-obj-$(CONFIG_DIMLIB) = net_dim.o
+obj-$(CONFIG_DIMLIB) += net_dim.o
+obj-$(CONFIG_DIMLIB) += blk_dim.o
 
 net_dim-y = \
 	dim.o		\
 	net_dim.o
+
+blk_dim-y = \
+	dim.o		\
+	blk_dim.o
diff --git a/lib/dim/blk_dim.c b/lib/dim/blk_dim.c
new file mode 100644
index 000000000000..49107c169b56
--- /dev/null
+++ b/lib/dim/blk_dim.c
@@ -0,0 +1,114 @@
+#include <linux/blk_dim.h>
+
+static inline int blk_dim_step(struct dim *dim)
+{
+	switch (dim->tune_state) {
+	case DIM_PARKING_ON_TOP:
+	case DIM_PARKING_TIRED:
+		break;
+	case DIM_GOING_RIGHT:
+		if (dim->profile_ix == (BLK_DIM_PARAMS_NUM_PROFILES - 1))
+			return DIM_ON_EDGE;
+		dim->profile_ix++;
+		dim->steps_right++;
+		break;
+	case DIM_GOING_LEFT:
+		if (dim->profile_ix == 0)
+			return DIM_ON_EDGE;
+		dim->profile_ix--;
+		dim->steps_left++;
+		break;
+	}
+
+	return DIM_STEPPED;
+}
+
+static inline int blk_dim_stats_compare(struct dim_stats *curr, struct dim_stats *prev)
+{
+	/* first stat */
+	if (!prev->cpms)
+		return DIM_STATS_SAME;
+
+	if (IS_SIGNIFICANT_DIFF(curr->cpms, prev->cpms))
+		return (curr->cpms > prev->cpms) ? DIM_STATS_BETTER :
+						DIM_STATS_WORSE;
+
+	if (IS_SIGNIFICANT_DIFF(curr->cpe_ratio, prev->cpe_ratio))
+		return (curr->cpe_ratio > prev->cpe_ratio) ? DIM_STATS_BETTER :
+						DIM_STATS_WORSE;
+
+	return DIM_STATS_SAME;
+}
+
+static inline bool blk_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
+{
+	int prev_ix = dim->profile_ix;
+	int stats_res;
+	int step_res;
+
+	switch (dim->tune_state) {
+	case DIM_PARKING_ON_TOP:
+		break;
+	case DIM_PARKING_TIRED:
+		break;
+
+	case DIM_GOING_RIGHT:
+	case DIM_GOING_LEFT:
+		stats_res = blk_dim_stats_compare(curr_stats, &dim->prev_stats);
+
+		switch (stats_res) {
+		case DIM_STATS_SAME:
+			if (curr_stats->cpe_ratio <= 50*prev_ix)
+				dim->profile_ix = 0;
+			break;
+		case DIM_STATS_WORSE:
+			dim_turn(dim);
+		default:
+		case DIM_STATS_BETTER:
+			/* fall through */
+			step_res = blk_dim_step(dim);
+			if (step_res == DIM_ON_EDGE)
+				dim_turn(dim);
+			break;
+		}
+		break;
+	}
+
+	dim->prev_stats = *curr_stats;
+
+	return dim->profile_ix != prev_ix;
+}
+
+void blk_dim(struct dim *dim, struct dim_sample end_sample)
+{
+	struct dim_stats curr_stats;
+	u16 nevents;
+
+	switch (dim->state) {
+	case DIM_MEASURE_IN_PROGRESS:
+		nevents = end_sample.event_ctr - dim->start_sample.event_ctr;
+		if (nevents < DIM_NEVENTS) {
+			dim_create_sample(end_sample.event_ctr, end_sample.pkt_ctr,
+				end_sample.byte_ctr, end_sample.comp_ctr, &dim->measuring_sample);
+			break;
+		}
+		dim_calc_stats(&dim->start_sample, &end_sample,
+				   &curr_stats);
+		if (blk_dim_decision(&curr_stats, dim)) {
+			dim->state = DIM_APPLY_NEW_PROFILE;
+			schedule_work(&dim->work);
+			break;
+		}
+		/* fall through */
+	case DIM_START_MEASURE:
+		dim->state = DIM_MEASURE_IN_PROGRESS;
+		dim_create_sample(end_sample.event_ctr, end_sample.pkt_ctr, end_sample.byte_ctr,
+				end_sample.comp_ctr, &dim->start_sample);
+		dim_create_sample(end_sample.event_ctr, end_sample.pkt_ctr, end_sample.byte_ctr,
+				end_sample.comp_ctr, &dim->measuring_sample);
+		break;
+	case DIM_APPLY_NEW_PROFILE:
+		break;
+	}
+}
+EXPORT_SYMBOL(blk_dim);
-- 
2.19.1

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