OpenZFS 8484 - Implement aggregate sum and use for arc counters

In pursuit of improving performance on multi-core systems, we should
implements fanned out counters and use them to improve the performance of
some of the arc statistics. These stats are updated extremely frequently,
and can consume a significant amount of CPU time.

Authored by: Paul Dagnelie <[email protected]>
Reviewed by: Pavel Zakharov <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Approved by: Dan McDonald <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Ported-by: Paul Dagnelie <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/8484
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7028a8b92b7
Issue #3752
Closes #7462

1 files changed, 59 insertions, 0 deletions

diff --git a/include/sys/aggsum.h b/include/sys/aggsum.h
new file mode 100644
index 000000000..caa08d773
--- /dev/null
+++ b/include/sys/aggsum.h
@@ -0,0 +1,59 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2017 by Delphix. All rights reserved.
+ */
+
+#ifndef	_SYS_AGGSUM_H
+#define	_SYS_AGGSUM_H
+
+#include <sys/zfs_context.h>
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+typedef struct aggsum_bucket aggsum_bucket_t;
+
+struct aggsum_bucket {
+	kmutex_t asc_lock;
+	int64_t asc_delta;
+	uint64_t asc_borrowed;
+} ____cacheline_aligned;
+
+/*
+ * Fan out over FANOUT cpus.
+ */
+typedef struct aggsum {
+	kmutex_t as_lock;
+	int64_t as_lower_bound;
+	int64_t as_upper_bound;
+	uint64_t as_numbuckets;
+	aggsum_bucket_t *as_buckets;
+} aggsum_t;
+
+void aggsum_init(aggsum_t *, uint64_t);
+void aggsum_fini(aggsum_t *);
+int64_t aggsum_lower_bound(aggsum_t *);
+int64_t aggsum_upper_bound(aggsum_t *);
+int aggsum_compare(aggsum_t *, uint64_t);
+uint64_t aggsum_value(aggsum_t *);
+void aggsum_add(aggsum_t *, int64_t);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif /* _SYS_AGGSUM_H */