Use wmsum for arc, abd, dbuf and zfetch statistics. (#12172)

wmsum was designed exactly for cases like these with many updates
and rare reads.  It allows to completely avoid atomic operations on
congested global variables.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Mark Maybee <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Sponsored-By: iXsystems, Inc.
Closes #12172

1 files changed, 46 insertions, 0 deletions

diff --git a/module/os/freebsd/zfs/abd_os.c b/module/os/freebsd/zfs/abd_os.c
index 00aa21c6c..47adc2278 100644
--- a/module/os/freebsd/zfs/abd_os.c
+++ b/module/os/freebsd/zfs/abd_os.c
@@ -69,6 +69,15 @@ static abd_stats_t abd_stats = {
 	{ "linear_data_size",			KSTAT_DATA_UINT64 },
 };
 
+struct {
+	wmsum_t abdstat_struct_size;
+	wmsum_t abdstat_scatter_cnt;
+	wmsum_t abdstat_scatter_data_size;
+	wmsum_t abdstat_scatter_chunk_waste;
+	wmsum_t abdstat_linear_cnt;
+	wmsum_t abdstat_linear_data_size;
+} abd_sums;
+
 /*
  * The size of the chunks ABD allocates. Because the sizes allocated from the
  * kmem_cache can't change, this tunable can only be modified at boot. Changing
@@ -271,16 +280,46 @@ abd_free_zero_scatter(void)
 	kmem_free(abd_zero_buf, zfs_abd_chunk_size);
 }
 
+static int
+abd_kstats_update(kstat_t *ksp, int rw)
+{
+	abd_stats_t *as = ksp->ks_data;
+
+	if (rw == KSTAT_WRITE)
+		return (EACCES);
+	as->abdstat_struct_size.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_struct_size);
+	as->abdstat_scatter_cnt.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_scatter_cnt);
+	as->abdstat_scatter_data_size.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_scatter_data_size);
+	as->abdstat_scatter_chunk_waste.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_scatter_chunk_waste);
+	as->abdstat_linear_cnt.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_linear_cnt);
+	as->abdstat_linear_data_size.value.ui64 =
+	    wmsum_value(&abd_sums.abdstat_linear_data_size);
+	return (0);
+}
+
 void
 abd_init(void)
 {
 	abd_chunk_cache = kmem_cache_create("abd_chunk", zfs_abd_chunk_size, 0,
 	    NULL, NULL, NULL, NULL, 0, KMC_NODEBUG);
 
+	wmsum_init(&abd_sums.abdstat_struct_size, 0);
+	wmsum_init(&abd_sums.abdstat_scatter_cnt, 0);
+	wmsum_init(&abd_sums.abdstat_scatter_data_size, 0);
+	wmsum_init(&abd_sums.abdstat_scatter_chunk_waste, 0);
+	wmsum_init(&abd_sums.abdstat_linear_cnt, 0);
+	wmsum_init(&abd_sums.abdstat_linear_data_size, 0);
+
 	abd_ksp = kstat_create("zfs", 0, "abdstats", "misc", KSTAT_TYPE_NAMED,
 	    sizeof (abd_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
 	if (abd_ksp != NULL) {
 		abd_ksp->ks_data = &abd_stats;
+		abd_ksp->ks_update = abd_kstats_update;
 		kstat_install(abd_ksp);
 	}
 
@@ -297,6 +336,13 @@ abd_fini(void)
 		abd_ksp = NULL;
 	}
 
+	wmsum_fini(&abd_sums.abdstat_struct_size);
+	wmsum_fini(&abd_sums.abdstat_scatter_cnt);
+	wmsum_fini(&abd_sums.abdstat_scatter_data_size);
+	wmsum_fini(&abd_sums.abdstat_scatter_chunk_waste);
+	wmsum_fini(&abd_sums.abdstat_linear_cnt);
+	wmsum_fini(&abd_sums.abdstat_linear_data_size);
+
 	kmem_cache_destroy(abd_chunk_cache);
 	abd_chunk_cache = NULL;
 }