commit 4c3cb6e2bdac23681cbe2a7a7aa6b58107c52ff4
Author: Mateusz Guzik <mjguzik@gmail.com>
Date:   Thu Oct 29 04:52:00 2020 -0400

    ztsd debug

diff --git a/sys/contrib/openzfs/module/zstd/zfs_zstd.c b/sys/contrib/openzfs/module/zstd/zfs_zstd.c
index 34c56b7a7fdf..9b7139c66f2b 100644
--- a/sys/contrib/openzfs/module/zstd/zfs_zstd.c
+++ b/sys/contrib/openzfs/module/zstd/zfs_zstd.c
@@ -50,6 +50,10 @@
 #include "lib/zstd.h"
 #include "lib/zstd_errors.h"
 
+//DEFINE_DTRACE_PROBE3(zstd__alloc);
+//DEFINE_DTRACE_PROBE2(zstd__alloc_miss1);
+//DEFINE_DTRACE_PROBE2(zstd__alloc_miss2);
+
 kstat_t *zstd_ksp = NULL;
 
 typedef struct zstd_stats {
@@ -216,6 +220,7 @@ zstd_mempool_alloc(struct zstd_pool *zstd_mempool, size_t size)
 {
 	struct zstd_pool *pool;
 	struct zstd_kmem *mem = NULL;
+	int contested = 0;
 
 	if (!zstd_mempool) {
 		return (NULL);
@@ -242,6 +247,7 @@ zstd_mempool_alloc(struct zstd_pool *zstd_mempool, size_t size)
 				pool->timeout = gethrestime_sec() +
 				    ZSTD_POOL_TIMEOUT;
 				mem = pool->mem;
+				DTRACE_PROBE3(zstd__alloc, size_t, size, size_t, pool->size, int, contested);
 				continue;
 			}
 
@@ -254,6 +260,8 @@ zstd_mempool_alloc(struct zstd_pool *zstd_mempool, size_t size)
 			}
 
 			mutex_exit(&pool->barrier);
+		} else {
+			contested++;
 		}
 	}
 
@@ -261,6 +269,8 @@ zstd_mempool_alloc(struct zstd_pool *zstd_mempool, size_t size)
 		return (mem);
 	}
 
+	DTRACE_PROBE2(zstd__alloc_miss1, size_t, size, int, contested);
+
 	/*
 	 * If no preallocated slot was found, try to fill in a new one.
 	 *
@@ -303,6 +313,7 @@ zstd_mempool_alloc(struct zstd_pool *zstd_mempool, size_t size)
 	 * instead.
 	 */
 	if (!mem) {
+		DTRACE_PROBE2(zstd__alloc_miss2, size_t, size, int, contested);
 		mem = vmem_alloc(size, KM_NOSLEEP);
 		if (mem) {
 			mem->pool = NULL;