Illumos 5445 - Add more visibility via arcstats

5445 Add more visibility via arcstats; specifically arc_state_t
stats and differentiate between "data" and "metadata"
Reviewed by: Basil Crow <basil.crow@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Bayard Bell <bayard.bell@nexenta.com>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  https://www.illumos.org/issues/5445
  https://github.com/illumos/illumos-gate/commit/4076b1b

Porting Notes:

This patch is an improved version of cc7f677 which was previously
merged in ZoL.  This patch incorporates the additional improvements
which were made upstream.

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #3533

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index d734a170fe5e49b2b6f1c8865668576c2c75fb09..27c38536650434353c221a3e0dc24a74541d00df 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -298,25 +298,137 @@ typedef struct arc_stats {
        kstat_named_t arcstat_c_min;
        kstat_named_t arcstat_c_max;
        kstat_named_t arcstat_size;
+       /*
+        * Number of bytes consumed by internal ARC structures necessary
+        * for tracking purposes; these structures are not actually
+        * backed by ARC buffers. This includes arc_buf_hdr_t structures
+        * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
+        * caches), and arc_buf_t structures (allocated via arc_buf_t
+        * cache).
+        */
        kstat_named_t arcstat_hdr_size;
+       /*
+        * Number of bytes consumed by ARC buffers of type equal to
+        * ARC_BUFC_DATA. This is generally consumed by buffers backing
+        * on disk user data (e.g. plain file contents).
+        */
        kstat_named_t arcstat_data_size;
-       kstat_named_t arcstat_meta_size;
+       /*
+        * Number of bytes consumed by ARC buffers of type equal to
+        * ARC_BUFC_METADATA. This is generally consumed by buffers
+        * backing on disk data that is used for internal ZFS
+        * structures (e.g. ZAP, dnode, indirect blocks, etc).
+        */
+       kstat_named_t arcstat_metadata_size;
+       /*
+        * Number of bytes consumed by various buffers and structures
+        * not actually backed with ARC buffers. This includes bonus
+        * buffers (allocated directly via zio_buf_* functions),
+        * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
+        * cache), and dnode_t structures (allocated via dnode_t cache).
+        */
        kstat_named_t arcstat_other_size;
+       /*
+        * Total number of bytes consumed by ARC buffers residing in the
+        * arc_anon state. This includes *all* buffers in the arc_anon
+        * state; e.g. data, metadata, evictable, and unevictable buffers
+        * are all included in this value.
+        */
        kstat_named_t arcstat_anon_size;
-       kstat_named_t arcstat_anon_evict_data;
-       kstat_named_t arcstat_anon_evict_metadata;
+       /*
+        * Number of bytes consumed by ARC buffers that meet the
+        * following criteria: backing buffers of type ARC_BUFC_DATA,
+        * residing in the arc_anon state, and are eligible for eviction
+        * (e.g. have no outstanding holds on the buffer).
+        */
+       kstat_named_t arcstat_anon_evictable_data;
+       /*
+        * Number of bytes consumed by ARC buffers that meet the
+        * following criteria: backing buffers of type ARC_BUFC_METADATA,
+        * residing in the arc_anon state, and are eligible for eviction
+        * (e.g. have no outstanding holds on the buffer).
+        */
+       kstat_named_t arcstat_anon_evictable_metadata;
+       /*
+        * Total number of bytes consumed by ARC buffers residing in the
+        * arc_mru state. This includes *all* buffers in the arc_mru
+        * state; e.g. data, metadata, evictable, and unevictable buffers
+        * are all included in this value.
+        */
        kstat_named_t arcstat_mru_size;
-       kstat_named_t arcstat_mru_evict_data;
-       kstat_named_t arcstat_mru_evict_metadata;
+       /*
+        * Number of bytes consumed by ARC buffers that meet the
+        * following criteria: backing buffers of type ARC_BUFC_DATA,
+        * residing in the arc_mru state, and are eligible for eviction
+        * (e.g. have no outstanding holds on the buffer).
+        */
+       kstat_named_t arcstat_mru_evictable_data;
+       /*
+        * Number of bytes consumed by ARC buffers that meet the
+        * following criteria: backing buffers of type ARC_BUFC_METADATA,
+        * residing in the arc_mru state, and are eligible for eviction
+        * (e.g. have no outstanding holds on the buffer).
+        */
+       kstat_named_t arcstat_mru_evictable_metadata;
+       /*
+        * Total number of bytes that *would have been* consumed by ARC
+        * buffers in the arc_mru_ghost state. The key thing to note
+        * here, is the fact that this size doesn't actually indicate
+        * RAM consumption. The ghost lists only consist of headers and
+        * don't actually have ARC buffers linked off of these headers.
+        * Thus, *if* the headers had associated ARC buffers, these
+        * buffers *would have* consumed this number of bytes.
+        */
        kstat_named_t arcstat_mru_ghost_size;
-       kstat_named_t arcstat_mru_ghost_evict_data;
-       kstat_named_t arcstat_mru_ghost_evict_metadata;
+       /*
+        * Number of bytes that *would have been* consumed by ARC
+        * buffers that are eligible for eviction, of type
+        * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
+        */
+       kstat_named_t arcstat_mru_ghost_evictable_data;
+       /*
+        * Number of bytes that *would have been* consumed by ARC
+        * buffers that are eligible for eviction, of type
+        * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
+        */
+       kstat_named_t arcstat_mru_ghost_evictable_metadata;
+       /*
+        * Total number of bytes consumed by ARC buffers residing in the
+        * arc_mfu state. This includes *all* buffers in the arc_mfu
+        * state; e.g. data, metadata, evictable, and unevictable buffers
+        * are all included in this value.
+        */
        kstat_named_t arcstat_mfu_size;
-       kstat_named_t arcstat_mfu_evict_data;
-       kstat_named_t arcstat_mfu_evict_metadata;
+       /*
+        * Number of bytes consumed by ARC buffers that are eligible for
+        * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
+        * state.
+        */
+       kstat_named_t arcstat_mfu_evictable_data;
+       /*
+        * Number of bytes consumed by ARC buffers that are eligible for
+        * eviction, of type ARC_BUFC_METADATA, and reside in the
+        * arc_mfu state.
+        */
+       kstat_named_t arcstat_mfu_evictable_metadata;
+       /*
+        * Total number of bytes that *would have been* consumed by ARC
+        * buffers in the arc_mfu_ghost state. See the comment above
+        * arcstat_mru_ghost_size for more details.
+        */
        kstat_named_t arcstat_mfu_ghost_size;
-       kstat_named_t arcstat_mfu_ghost_evict_data;
-       kstat_named_t arcstat_mfu_ghost_evict_metadata;
+       /*
+        * Number of bytes that *would have been* consumed by ARC
+        * buffers that are eligible for eviction, of type
+        * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
+        */
+       kstat_named_t arcstat_mfu_ghost_evictable_data;
+       /*
+        * Number of bytes that *would have been* consumed by ARC
+        * buffers that are eligible for eviction, of type
+        * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
+        */
+       kstat_named_t arcstat_mfu_ghost_evictable_metadata;
        kstat_named_t arcstat_l2_hits;
        kstat_named_t arcstat_l2_misses;
        kstat_named_t arcstat_l2_feeds;
@@ -392,23 +504,23 @@ static arc_stats_t arc_stats = {
        { "size",                       KSTAT_DATA_UINT64 },
        { "hdr_size",                   KSTAT_DATA_UINT64 },
        { "data_size",                  KSTAT_DATA_UINT64 },
-       { "meta_size",                  KSTAT_DATA_UINT64 },
+       { "metadata_size",              KSTAT_DATA_UINT64 },
        { "other_size",                 KSTAT_DATA_UINT64 },
        { "anon_size",                  KSTAT_DATA_UINT64 },
-       { "anon_evict_data",            KSTAT_DATA_UINT64 },
-       { "anon_evict_metadata",        KSTAT_DATA_UINT64 },
+       { "anon_evictable_data",        KSTAT_DATA_UINT64 },
+       { "anon_evictable_metadata",    KSTAT_DATA_UINT64 },
        { "mru_size",                   KSTAT_DATA_UINT64 },
-       { "mru_evict_data",             KSTAT_DATA_UINT64 },
-       { "mru_evict_metadata",         KSTAT_DATA_UINT64 },
+       { "mru_evictable_data",         KSTAT_DATA_UINT64 },
+       { "mru_evictable_metadata",     KSTAT_DATA_UINT64 },
        { "mru_ghost_size",             KSTAT_DATA_UINT64 },
-       { "mru_ghost_evict_data",       KSTAT_DATA_UINT64 },
-       { "mru_ghost_evict_metadata",   KSTAT_DATA_UINT64 },
+       { "mru_ghost_evictable_data",   KSTAT_DATA_UINT64 },
+       { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
        { "mfu_size",                   KSTAT_DATA_UINT64 },
-       { "mfu_evict_data",             KSTAT_DATA_UINT64 },
-       { "mfu_evict_metadata",         KSTAT_DATA_UINT64 },
+       { "mfu_evictable_data",         KSTAT_DATA_UINT64 },
+       { "mfu_evictable_metadata",     KSTAT_DATA_UINT64 },
        { "mfu_ghost_size",             KSTAT_DATA_UINT64 },
-       { "mfu_ghost_evict_data",       KSTAT_DATA_UINT64 },
-       { "mfu_ghost_evict_metadata",   KSTAT_DATA_UINT64 },
+       { "mfu_ghost_evictable_data",   KSTAT_DATA_UINT64 },
+       { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
        { "l2_hits",                    KSTAT_DATA_UINT64 },
        { "l2_misses",                  KSTAT_DATA_UINT64 },
        { "l2_feeds",                   KSTAT_DATA_UINT64 },
@@ -446,7 +558,7 @@ static arc_stats_t arc_stats = {
        { "arc_meta_used",              KSTAT_DATA_UINT64 },
        { "arc_meta_limit",             KSTAT_DATA_UINT64 },
        { "arc_meta_max",               KSTAT_DATA_UINT64 },
-       { "arc_meta_min",               KSTAT_DATA_UINT64 },
+       { "arc_meta_min",               KSTAT_DATA_UINT64 }
 };
 
 #define        ARCSTAT(stat)   (arc_stats.stat.value.ui64)
@@ -1470,7 +1582,7 @@ arc_space_consume(uint64_t space, arc_space_type_t type)
                ARCSTAT_INCR(arcstat_data_size, space);
                break;
        case ARC_SPACE_META:
-               ARCSTAT_INCR(arcstat_meta_size, space);
+               ARCSTAT_INCR(arcstat_metadata_size, space);
                break;
        case ARC_SPACE_OTHER:
                ARCSTAT_INCR(arcstat_other_size, space);
@@ -1483,11 +1595,8 @@ arc_space_consume(uint64_t space, arc_space_type_t type)
                break;
        }
 
-       if (type != ARC_SPACE_DATA) {
+       if (type != ARC_SPACE_DATA)
                ARCSTAT_INCR(arcstat_meta_used, space);
-               if (arc_meta_max < arc_meta_used)
-                       arc_meta_max = arc_meta_used;
-       }
 
        atomic_add_64(&arc_size, space);
 }
@@ -1504,7 +1613,7 @@ arc_space_return(uint64_t space, arc_space_type_t type)
                ARCSTAT_INCR(arcstat_data_size, -space);
                break;
        case ARC_SPACE_META:
-               ARCSTAT_INCR(arcstat_meta_size, -space);
+               ARCSTAT_INCR(arcstat_metadata_size, -space);
                break;
        case ARC_SPACE_OTHER:
                ARCSTAT_INCR(arcstat_other_size, -space);
@@ -1519,6 +1628,8 @@ arc_space_return(uint64_t space, arc_space_type_t type)
 
        if (type != ARC_SPACE_DATA) {
                ASSERT(arc_meta_used >= space);
+               if (arc_meta_max < arc_meta_used)
+                       arc_meta_max = arc_meta_used;
                ARCSTAT_INCR(arcstat_meta_used, -space);
        }
 
@@ -4971,28 +5082,28 @@ arc_kstat_update(kstat_t *ksp, int rw)
        arc_stats_t *as = ksp->ks_data;
 
        if (rw == KSTAT_WRITE) {
-               return (SET_ERROR(EACCES));
+               return (EACCES);
        } else {
                arc_kstat_update_state(arc_anon,
                    &as->arcstat_anon_size,
-                   &as->arcstat_anon_evict_data,
-                   &as->arcstat_anon_evict_metadata);
+                   &as->arcstat_anon_evictable_data,
+                   &as->arcstat_anon_evictable_metadata);
                arc_kstat_update_state(arc_mru,
                    &as->arcstat_mru_size,
-                   &as->arcstat_mru_evict_data,
-                   &as->arcstat_mru_evict_metadata);
+                   &as->arcstat_mru_evictable_data,
+                   &as->arcstat_mru_evictable_metadata);
                arc_kstat_update_state(arc_mru_ghost,
                    &as->arcstat_mru_ghost_size,
-                   &as->arcstat_mru_ghost_evict_data,
-                   &as->arcstat_mru_ghost_evict_metadata);
+                   &as->arcstat_mru_ghost_evictable_data,
+                   &as->arcstat_mru_ghost_evictable_metadata);
                arc_kstat_update_state(arc_mfu,
                    &as->arcstat_mfu_size,
-                   &as->arcstat_mfu_evict_data,
-                   &as->arcstat_mfu_evict_metadata);
+                   &as->arcstat_mfu_evictable_data,
+                   &as->arcstat_mfu_evictable_metadata);
                arc_kstat_update_state(arc_mfu_ghost,
                    &as->arcstat_mfu_ghost_size,
-                   &as->arcstat_mfu_ghost_evict_data,
-                   &as->arcstat_mfu_ghost_evict_metadata);
+                   &as->arcstat_mfu_ghost_evictable_data,
+                   &as->arcstat_mfu_ghost_evictable_metadata);
        }
 
        return (0);