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arc_evict, arc_evict_ghost: reduce stack usage using kmem_zalloc

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With debugging enabled and depending on your kernel config, the size of
arc_buf_hdr_t can blow out the stack of arc_evict() and arc_evict_ghost()
to greater than 1024 bytes. Let's avoid this.

Signed-off-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3377
This commit is contained in:
Chris Dunlop 2015-05-06 09:59:17 +10:00 committed by Brian Behlendorf
parent 63e3a8616b
commit 16fcdea363
1 changed files with 20 additions and 12 deletions
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32
module/zfs/arc.c
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@ -1825,13 +1825,15 @@ arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
kmutex_t *hash_lock; kmutex_t *hash_lock;
boolean_t have_lock; boolean_t have_lock;
void *stolen = NULL; void *stolen = NULL;
arc_buf_hdr_t marker = {{{ 0 }}}; arc_buf_hdr_t *marker;
int count = 0; int count = 0;
ASSERT(state == arc_mru || state == arc_mfu); ASSERT(state == arc_mru || state == arc_mfu);
evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
marker = kmem_zalloc(sizeof (arc_buf_hdr_t), KM_SLEEP);
top: top:
mutex_enter(&state->arcs_mtx); mutex_enter(&state->arcs_mtx);
mutex_enter(&evicted_state->arcs_mtx); mutex_enter(&evicted_state->arcs_mtx);
@ -1866,14 +1868,14 @@ top:
* the hot code path, so don't sleep. * the hot code path, so don't sleep.
*/ */
if (!recycle && count++ > arc_evict_iterations) { 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(&evicted_state->arcs_mtx);
mutex_exit(&state->arcs_mtx); mutex_exit(&state->arcs_mtx);
kpreempt(KPREEMPT_SYNC); kpreempt(KPREEMPT_SYNC);
mutex_enter(&state->arcs_mtx); mutex_enter(&state->arcs_mtx);
mutex_enter(&evicted_state->arcs_mtx); mutex_enter(&evicted_state->arcs_mtx);
ab_prev = list_prev(list, &marker); ab_prev = list_prev(list, marker);
list_remove(list, &marker); list_remove(list, marker);
count = 0; count = 0;
continue; continue;
} }
@ -1957,6 +1959,8 @@ top:
goto top; goto top;
} }
kmem_free(marker, sizeof (arc_buf_hdr_t));
if (bytes_evicted < bytes) if (bytes_evicted < bytes)
dprintf("only evicted %lld bytes from %x\n", dprintf("only evicted %lld bytes from %x\n",
(longlong_t)bytes_evicted, state->arcs_state); (longlong_t)bytes_evicted, state->arcs_state);
@ -1986,7 +1990,7 @@ arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes,
arc_buf_contents_t type) arc_buf_contents_t type)
{ {
arc_buf_hdr_t *ab, *ab_prev; arc_buf_hdr_t *ab, *ab_prev;
arc_buf_hdr_t marker; arc_buf_hdr_t *marker;
list_t *list = &state->arcs_list[type]; list_t *list = &state->arcs_list[type];
kmutex_t *hash_lock; kmutex_t *hash_lock;
uint64_t bytes_deleted = 0; uint64_t bytes_deleted = 0;
@ -1994,7 +1998,9 @@ arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes,
int count = 0; int count = 0;
ASSERT(GHOST_STATE(state)); ASSERT(GHOST_STATE(state));
bzero(&marker, sizeof (marker));
marker = kmem_zalloc(sizeof (arc_buf_hdr_t), KM_SLEEP);
top: top:
mutex_enter(&state->arcs_mtx); mutex_enter(&state->arcs_mtx);
for (ab = list_tail(list); ab; ab = ab_prev) { for (ab = list_tail(list); ab; ab = ab_prev) {
@ -2020,12 +2026,12 @@ top:
* before reacquiring the lock. * before reacquiring the lock.
*/ */
if (count++ > arc_evict_iterations) { if (count++ > arc_evict_iterations) {
list_insert_after(list, ab, &marker); list_insert_after(list, ab, marker);
mutex_exit(&state->arcs_mtx); mutex_exit(&state->arcs_mtx);
kpreempt(KPREEMPT_SYNC); kpreempt(KPREEMPT_SYNC);
mutex_enter(&state->arcs_mtx); mutex_enter(&state->arcs_mtx);
ab_prev = list_prev(list, &marker); ab_prev = list_prev(list, marker);
list_remove(list, &marker); list_remove(list, marker);
count = 0; count = 0;
continue; continue;
} }
@ -2057,13 +2063,13 @@ top:
* hash lock to become available. Once its * hash lock to become available. Once its
* available, restart from where we left off. * 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_exit(&state->arcs_mtx);
mutex_enter(hash_lock); mutex_enter(hash_lock);
mutex_exit(hash_lock); mutex_exit(hash_lock);
mutex_enter(&state->arcs_mtx); mutex_enter(&state->arcs_mtx);
ab_prev = list_prev(list, &marker); ab_prev = list_prev(list, marker);
list_remove(list, &marker); list_remove(list, marker);
} else { } else {
bufs_skipped += 1; bufs_skipped += 1;
} }
@ -2076,6 +2082,8 @@ top:
goto top; goto top;
} }
kmem_free(marker, sizeof (arc_buf_hdr_t));
if (bufs_skipped) { if (bufs_skipped) {
ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
ASSERT(bytes >= 0); ASSERT(bytes >= 0);