Revert "arc_evict, arc_evict_ghost: reduce stack usage using kmem_zalloc"

This reverts commit 16fcdea36340c658b4557fd34a74915fd618f7a6 in preparation
for the illumos 5497 "lock contention on arcs_mtx" patch which eliminates
"marker" within the ARC code.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 1699ea7e7e7a29081f5f625103e8be573bfd94a0..9882295b9cf8f0312fa08446eddc4c0ef0a8422a 100644 (file)
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -1825,15 +1825,13 @@ arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
        kmutex_t *hash_lock;
        boolean_t have_lock;
        void *stolen = NULL;
-       arc_buf_hdr_t *marker;
+       arc_buf_hdr_t marker = {{{ 0 }}};
        int count = 0;
 
        ASSERT(state == arc_mru || state == arc_mfu);
 
        evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
 
-       marker = kmem_zalloc(sizeof (arc_buf_hdr_t), KM_SLEEP);
-
 top:
        mutex_enter(&state->arcs_mtx);
        mutex_enter(&evicted_state->arcs_mtx);
@@ -1868,14 +1866,14 @@ top:
                 * the hot code path, so don't sleep.
                 */
                if (!recycle && count++ > arc_evict_iterations) {
-                       list_insert_after(list, ab, marker);
+                       list_insert_after(list, ab, &marker);
                        mutex_exit(&evicted_state->arcs_mtx);
                        mutex_exit(&state->arcs_mtx);
                        kpreempt(KPREEMPT_SYNC);
                        mutex_enter(&state->arcs_mtx);
                        mutex_enter(&evicted_state->arcs_mtx);
-                       ab_prev = list_prev(list, marker);
-                       list_remove(list, marker);
+                       ab_prev = list_prev(list, &marker);
+                       list_remove(list, &marker);
                        count = 0;
                        continue;
                }
@@ -1959,8 +1957,6 @@ top:
                goto top;
        }
 
-       kmem_free(marker, sizeof (arc_buf_hdr_t));
-
        if (bytes_evicted < bytes)
                dprintf("only evicted %lld bytes from %x\n",
                    (longlong_t)bytes_evicted, state->arcs_state);
@@ -1990,7 +1986,7 @@ arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes,
     arc_buf_contents_t type)
 {
        arc_buf_hdr_t *ab, *ab_prev;
-       arc_buf_hdr_t *marker;
+       arc_buf_hdr_t marker;
        list_t *list = &state->arcs_list[type];
        kmutex_t *hash_lock;
        uint64_t bytes_deleted = 0;
@@ -1998,9 +1994,7 @@ arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes,
        int count = 0;
 
        ASSERT(GHOST_STATE(state));
-
-       marker = kmem_zalloc(sizeof (arc_buf_hdr_t), KM_SLEEP);
-
+       bzero(&marker, sizeof (marker));
 top:
        mutex_enter(&state->arcs_mtx);
        for (ab = list_tail(list); ab; ab = ab_prev) {
@@ -2026,12 +2020,12 @@ top:
                 * before reacquiring the lock.
                 */
                if (count++ > arc_evict_iterations) {
-                       list_insert_after(list, ab, marker);
+                       list_insert_after(list, ab, &marker);
                        mutex_exit(&state->arcs_mtx);
                        kpreempt(KPREEMPT_SYNC);
                        mutex_enter(&state->arcs_mtx);
-                       ab_prev = list_prev(list, marker);
-                       list_remove(list, marker);
+                       ab_prev = list_prev(list, &marker);
+                       list_remove(list, &marker);
                        count = 0;
                        continue;
                }
@@ -2063,13 +2057,13 @@ top:
                         * hash lock to become available. Once its
                         * available, restart from where we left off.
                         */
-                       list_insert_after(list, ab, marker);
+                       list_insert_after(list, ab, &marker);
                        mutex_exit(&state->arcs_mtx);
                        mutex_enter(hash_lock);
                        mutex_exit(hash_lock);
                        mutex_enter(&state->arcs_mtx);
-                       ab_prev = list_prev(list, marker);
-                       list_remove(list, marker);
+                       ab_prev = list_prev(list, &marker);
+                       list_remove(list, &marker);
                } else {
                        bufs_skipped += 1;
                }
@@ -2082,8 +2076,6 @@ top:
                goto top;
        }
 
-       kmem_free(marker, sizeof (arc_buf_hdr_t));
-
        if (bufs_skipped) {
                ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
                ASSERT(bytes >= 0);