linux-kernel - [PATCH 10/10] time_stats: Kill TIME_STATS_HAVE

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Message-ID: <170873668101.1860949.4100731238233533238.stgit@frogsfrogsfrogs>
Date: Fri, 23 Feb 2024 17:12:42 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: akpm@...ux-foundation.org, daniel@...o.nz, kent.overstreet@...ux.dev,
 djwong@...nel.org
Cc: linux-xfs@...r.kernel.org, linux-bcachefs@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: [PATCH 10/10] time_stats: Kill TIME_STATS_HAVE_QUANTILES

From: Kent Overstreet <kent.overstreet@...ux.dev>

We have 4 spare bytes next to the spinlock, no need for bit stuffing

Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
Reviewed-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Darrick J. Wong <djwong@...nel.org>
---
 include/linux/time_stats.h |   19 +++++--------------
 lib/time_stats.c           |    4 ++--
 2 files changed, 7 insertions(+), 16 deletions(-)


diff --git a/include/linux/time_stats.h b/include/linux/time_stats.h
index 4e1f5485ed039..6df2b34aa274b 100644
--- a/include/linux/time_stats.h
+++ b/include/linux/time_stats.h
@@ -68,6 +68,7 @@ struct time_stat_buffer {
 
 struct time_stats {
 	spinlock_t	lock;
+	bool		have_quantiles;
 	/* all fields are in nanoseconds */
 	u64             min_duration;
 	u64		max_duration;
@@ -87,12 +88,6 @@ struct time_stats {
 	struct mean_and_variance_weighted freq_stats_weighted;
 	struct time_stat_buffer __percpu *buffer;
 
-/*
- * Is this really a struct time_stats_quantiled?  Hide this flag in the least
- * significant bit of the start time to avoid blowing up the structure size.
- */
-#define TIME_STATS_HAVE_QUANTILES	(1ULL << 0)
-
 	u64		start_time;
 };
 
@@ -103,13 +98,9 @@ struct time_stats_quantiles {
 
 static inline struct quantiles *time_stats_to_quantiles(struct time_stats *stats)
 {
-	struct time_stats_quantiles *statq;
-
-	if (!(stats->start_time & TIME_STATS_HAVE_QUANTILES))
-		return NULL;
-
-	statq = container_of(stats, struct time_stats_quantiles, stats);
-	return &statq->quantiles;
+	return stats->have_quantiles
+		? &container_of(stats, struct time_stats_quantiles, stats)->quantiles
+		: NULL;
 }
 
 void __time_stats_clear_buffer(struct time_stats *, struct time_stat_buffer *);
@@ -169,7 +160,7 @@ static inline void time_stats_quantiles_exit(struct time_stats_quantiles *statq)
 static inline void time_stats_quantiles_init(struct time_stats_quantiles *statq)
 {
 	time_stats_init(&statq->stats);
-	statq->stats.start_time |= TIME_STATS_HAVE_QUANTILES;
+	statq->stats.have_quantiles = true;
 	memset(&statq->quantiles, 0, sizeof(statq->quantiles));
 }
 
diff --git a/lib/time_stats.c b/lib/time_stats.c
index c0f209dd9f6dd..0b90c80cba9f1 100644
--- a/lib/time_stats.c
+++ b/lib/time_stats.c
@@ -164,7 +164,7 @@ static void seq_buf_time_units_aligned(struct seq_buf *out, u64 ns)
 
 static inline u64 time_stats_lifetime(const struct time_stats *stats)
 {
-	return local_clock() - (stats->start_time & ~TIME_STATS_HAVE_QUANTILES);
+	return local_clock() - stats->start_time;
 }
 
 void time_stats_to_seq_buf(struct seq_buf *out, struct time_stats *stats,
@@ -364,7 +364,7 @@ void time_stats_init(struct time_stats *stats)
 	memset(stats, 0, sizeof(*stats));
 	stats->min_duration = U64_MAX;
 	stats->min_freq = U64_MAX;
-	stats->start_time = local_clock() & ~TIME_STATS_HAVE_QUANTILES;
+	stats->start_time = local_clock();
 	spin_lock_init(&stats->lock);
 }
 EXPORT_SYMBOL_GPL(time_stats_init);