X-Git-Url: https://git.camperquake.de/gitweb.cgi?a=blobdiff_plain;f=module%2Fzfs%2Farc.c;h=9ca8ad17d75d37d4a4d11f138ac9cc0b99133ebd;hb=0d3ac5e7356d29fbb7d2880c0a0c457656355ca0;hp=63b659b9a8c56ae79dcfa4baaa1aae4d596cd071;hpb=1834f2d8b715d25bafbb0e4a099994f45c3211ae;p=zfs.git

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 63b659b..9ca8ad1 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -282,6 +282,8 @@ typedef struct arc_stats {
 	kstat_named_t arcstat_l2_size;
 	kstat_named_t arcstat_l2_hdr_size;
 	kstat_named_t arcstat_memory_throttle_count;
+	kstat_named_t arcstat_memory_direct_count;
+	kstat_named_t arcstat_memory_indirect_count;
 	kstat_named_t arcstat_no_grow;
 	kstat_named_t arcstat_tempreserve;
 	kstat_named_t arcstat_loaned_bytes;
@@ -344,6 +346,8 @@ static arc_stats_t arc_stats = {
 	{ "l2_size",			KSTAT_DATA_UINT64 },
 	{ "l2_hdr_size",		KSTAT_DATA_UINT64 },
 	{ "memory_throttle_count",	KSTAT_DATA_UINT64 },
+	{ "memory_direct_count",	KSTAT_DATA_UINT64 },
+	{ "memory_indirect_count",	KSTAT_DATA_UINT64 },
 	{ "arc_no_grow",		KSTAT_DATA_UINT64 },
 	{ "arc_tempreserve",		KSTAT_DATA_UINT64 },
 	{ "arc_loaned_bytes",		KSTAT_DATA_UINT64 },
@@ -2171,6 +2175,51 @@ arc_reclaim_thread(void)
 	thread_exit();
 }
 
+#ifdef _KERNEL
+/*
+ * Under Linux the arc shrinker may be called for synchronous (direct)
+ * reclaim, or asynchronous (indirect) reclaim.  When called by kswapd
+ * for indirect reclaim we take a conservative approach and just reap
+ * free slabs from the ARC caches.  If this proves to be insufficient
+ * direct reclaim will be trigger.  In direct reclaim a more aggressive
+ * strategy is used, data is evicted from the ARC and free slabs reaped.
+ */
+SPL_SHRINKER_CALLBACK_PROTO(arc_shrinker_func, cb, nr_to_scan, gfp_mask)
+{
+	arc_reclaim_strategy_t strategy;
+	int arc_reclaim;
+
+	/* Not allowed to perform filesystem reclaim */
+	if (!(gfp_mask & __GFP_FS))
+		return (-1);
+
+	/* Return number of reclaimable pages based on arc_shrink_shift */
+	arc_reclaim = btop((arc_size - arc_c_min)) >> arc_shrink_shift;
+	if (nr_to_scan == 0)
+		return (arc_reclaim);
+
+	/* Reclaim in progress */
+	if (mutex_tryenter(&arc_reclaim_thr_lock) == 0)
+		return (-1);
+
+	if (current_is_kswapd()) {
+		strategy = ARC_RECLAIM_CONS;
+		ARCSTAT_INCR(arcstat_memory_indirect_count, 1);
+	} else {
+		strategy = ARC_RECLAIM_AGGR;
+		ARCSTAT_INCR(arcstat_memory_direct_count, 1);
+	}
+
+	arc_kmem_reap_now(strategy);
+	arc_reclaim = btop((arc_size - arc_c_min)) >> arc_shrink_shift;
+	mutex_exit(&arc_reclaim_thr_lock);
+
+	return (arc_reclaim);
+}
+
+SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
+#endif /* _KERNEL */
+
 /*
  * Adapt arc info given the number of bytes we are trying to add and
  * the state that we are comming from.  This function is only called
@@ -3485,6 +3534,12 @@ arc_init(void)
 	 * need to limit the cache to 1/8 of VM size.
 	 */
 	arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
+	/*
+	 * Register a shrinker to support synchronous (direct) memory
+	 * reclaim from the arc.  This is done to prevent kswapd from
+	 * swapping out pages when it is preferable to shrink the arc.
+	 */
+	spl_register_shrinker(&arc_shrinker);
 #endif
 
 	/* set min cache to 1/32 of all memory, or 64MB, whichever is more */
@@ -3602,6 +3657,10 @@ void
 arc_fini(void)
 {
 	mutex_enter(&arc_reclaim_thr_lock);
+#ifdef _KERNEL
+	spl_unregister_shrinker(&arc_shrinker);
+#endif /* _KERNEL */
+
 	arc_thread_exit = 1;
 	while (arc_thread_exit != 0)
 		cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);