} arc_reclaim_strategy_t;
/* number of seconds before growing cache again */
-static int arc_grow_retry = 60;
+static int arc_grow_retry = 5;
+
+/* expiration time for arc_no_grow */
+static clock_t arc_grow_time = 0;
/* shift of arc_c for calculating both min and max arc_p */
static int arc_p_min_shift = 4;
arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
}
-/*
- * Reclaim callback -- invoked when memory is low.
- */
-/* ARGSUSED */
-static void
-hdr_recl(void *unused)
-{
- /*
- * umem calls the reclaim func when we destroy the buf cache,
- * which is after we do arc_fini().
- */
- if (!arc_dead)
- cv_signal(&arc_reclaim_thr_cv);
-}
-
static void
buf_init(void)
{
}
hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
- 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
+ 0, hdr_cons, hdr_dest, NULL, NULL, NULL, 0);
buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
}
void
-arc_shrink(void)
+arc_shrink(uint64_t bytes)
{
if (arc_c > arc_c_min) {
uint64_t to_free;
-#ifdef _KERNEL
- to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
-#else
- to_free = arc_c >> arc_shrink_shift;
-#endif
+ to_free = bytes ? bytes : arc_c >> arc_shrink_shift;
+
if (arc_c > arc_c_min + to_free)
atomic_add_64(&arc_c, -to_free);
else
arc_adjust();
}
-static int
-arc_reclaim_needed(void)
-{
-#ifdef _KERNEL
- uint64_t extra;
-
- if (needfree)
- return (1);
-
- /*
- * take 'desfree' extra pages, so we reclaim sooner, rather than later
- */
- extra = desfree;
-
- /*
- * check that we're out of range of the pageout scanner. It starts to
- * schedule paging if freemem is less than lotsfree and needfree.
- * lotsfree is the high-water mark for pageout, and needfree is the
- * number of needed free pages. We add extra pages here to make sure
- * the scanner doesn't start up while we're freeing memory.
- */
- if (freemem < lotsfree + needfree + extra)
- return (1);
-
- /*
- * check to make sure that swapfs has enough space so that anon
- * reservations can still succeed. anon_resvmem() checks that the
- * availrmem is greater than swapfs_minfree, and the number of reserved
- * swap pages. We also add a bit of extra here just to prevent
- * circumstances from getting really dire.
- */
- if (availrmem < swapfs_minfree + swapfs_reserve + extra)
- return (1);
-
-#if defined(__i386)
- /*
- * If we're on an i386 platform, it's possible that we'll exhaust the
- * kernel heap space before we ever run out of available physical
- * memory. Most checks of the size of the heap_area compare against
- * tune.t_minarmem, which is the minimum available real memory that we
- * can have in the system. However, this is generally fixed at 25 pages
- * which is so low that it's useless. In this comparison, we seek to
- * calculate the total heap-size, and reclaim if more than 3/4ths of the
- * heap is allocated. (Or, in the calculation, if less than 1/4th is
- * free)
- */
- if (btop(vmem_size(heap_arena, VMEM_FREE)) <
- (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
- return (1);
-#endif
-
-#else
- if (spa_get_random(100) == 0)
- return (1);
-#endif
- return (0);
-}
-
static void
-arc_kmem_reap_now(arc_reclaim_strategy_t strat)
+arc_kmem_reap_now(arc_reclaim_strategy_t strat, uint64_t bytes)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
* reap free buffers from the arc kmem caches.
*/
if (strat == ARC_RECLAIM_AGGR)
- arc_shrink();
+ arc_shrink(bytes);
for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
if (zio_buf_cache[i] != prev_cache) {
kmem_cache_reap_now(hdr_cache);
}
+/*
+ * Unlike other ZFS implementations this thread is only responsible for
+ * adapting the target ARC size on Linux. The responsibility for memory
+ * reclamation has been entirely delegated to the arc_shrinker_func()
+ * which is registered with the VM. To reflect this change in behavior
+ * the arc_reclaim thread has been renamed to arc_adapt.
+ */
static void
-arc_reclaim_thread(void)
+arc_adapt_thread(void)
{
- clock_t growtime = 0;
- arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
callb_cpr_t cpr;
int64_t prune;
mutex_enter(&arc_reclaim_thr_lock);
while (arc_thread_exit == 0) {
- if (arc_reclaim_needed()) {
+#ifndef _KERNEL
+ arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
+
+ if (spa_get_random(100) == 0) {
if (arc_no_grow) {
if (last_reclaim == ARC_RECLAIM_CONS) {
}
/* reset the growth delay for every reclaim */
- growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
+ arc_grow_time = ddi_get_lbolt()+(arc_grow_retry * hz);
- arc_kmem_reap_now(last_reclaim);
+ arc_kmem_reap_now(last_reclaim, 0);
arc_warm = B_TRUE;
+ }
+#endif /* !_KERNEL */
- } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
+ /* No recent memory pressure allow the ARC to grow. */
+ if (arc_no_grow && ddi_get_lbolt() >= arc_grow_time)
arc_no_grow = FALSE;
- }
/*
* Keep meta data usage within limits, arc_shrink() is not
#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.
+ * Determine the amount of memory eligible for eviction contained in the
+ * ARC. All clean data reported by the ghost lists can always be safely
+ * evicted. Due to arc_c_min, the same does not hold for all clean data
+ * contained by the regular mru and mfu lists.
+ *
+ * In the case of the regular mru and mfu lists, we need to report as
+ * much clean data as possible, such that evicting that same reported
+ * data will not bring arc_size below arc_c_min. Thus, in certain
+ * circumstances, the total amount of clean data in the mru and mfu
+ * lists might not actually be evictable.
+ *
+ * The following two distinct cases are accounted for:
+ *
+ * 1. The sum of the amount of dirty data contained by both the mru and
+ * mfu lists, plus the ARC's other accounting (e.g. the anon list),
+ * is greater than or equal to arc_c_min.
+ * (i.e. amount of dirty data >= arc_c_min)
+ *
+ * This is the easy case; all clean data contained by the mru and mfu
+ * lists is evictable. Evicting all clean data can only drop arc_size
+ * to the amount of dirty data, which is greater than arc_c_min.
+ *
+ * 2. The sum of the amount of dirty data contained by both the mru and
+ * mfu lists, plus the ARC's other accounting (e.g. the anon list),
+ * is less than arc_c_min.
+ * (i.e. arc_c_min > amount of dirty data)
+ *
+ * 2.1. arc_size is greater than or equal arc_c_min.
+ * (i.e. arc_size >= arc_c_min > amount of dirty data)
+ *
+ * In this case, not all clean data from the regular mru and mfu
+ * lists is actually evictable; we must leave enough clean data
+ * to keep arc_size above arc_c_min. Thus, the maximum amount of
+ * evictable data from the two lists combined, is exactly the
+ * difference between arc_size and arc_c_min.
+ *
+ * 2.2. arc_size is less than arc_c_min
+ * (i.e. arc_c_min > arc_size > amount of dirty data)
+ *
+ * In this case, none of the data contained in the mru and mfu
+ * lists is evictable, even if it's clean. Since arc_size is
+ * already below arc_c_min, evicting any more would only
+ * increase this negative difference.
*/
+static uint64_t
+arc_evictable_memory(void) {
+ uint64_t arc_clean =
+ arc_mru->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
+ uint64_t ghost_clean =
+ arc_mru_ghost->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mru_ghost->arcs_lsize[ARC_BUFC_METADATA] +
+ arc_mfu_ghost->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mfu_ghost->arcs_lsize[ARC_BUFC_METADATA];
+ uint64_t arc_dirty = MAX((int64_t)arc_size - (int64_t)arc_clean, 0);
+
+ if (arc_dirty >= arc_c_min)
+ return (ghost_clean + arc_clean);
+
+ return (ghost_clean + MAX((int64_t)arc_size - (int64_t)arc_c_min, 0));
+}
+
static int
__arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
{
- arc_reclaim_strategy_t strategy;
- int arc_reclaim;
+ uint64_t pages;
- /* Return number of reclaimable pages based on arc_shrink_shift */
- arc_reclaim = MAX(btop(((int64_t)arc_size - (int64_t)arc_c_min))
- >> arc_shrink_shift, 0);
- if (sc->nr_to_scan == 0)
- return (arc_reclaim);
+ /* The arc is considered warm once reclaim has occurred */
+ if (unlikely(arc_warm == B_FALSE))
+ arc_warm = B_TRUE;
- /* Prevent reclaim below arc_c_min */
- if (arc_reclaim <= 0)
- return (-1);
+ /* Return the potential number of reclaimable pages */
+ pages = btop(arc_evictable_memory());
+ if (sc->nr_to_scan == 0)
+ return (pages);
/* Not allowed to perform filesystem reclaim */
if (!(sc->gfp_mask & __GFP_FS))
if (mutex_tryenter(&arc_reclaim_thr_lock) == 0)
return (-1);
+ /*
+ * Evict the requested number of pages by shrinking arc_c the
+ * requested amount. If there is nothing left to evict just
+ * reap whatever we can from the various arc slabs.
+ */
+ if (pages > 0) {
+ arc_kmem_reap_now(ARC_RECLAIM_AGGR, ptob(sc->nr_to_scan));
+ pages = btop(arc_evictable_memory());
+ } else {
+ arc_kmem_reap_now(ARC_RECLAIM_CONS, ptob(sc->nr_to_scan));
+ pages = -1;
+ }
+
+ /*
+ * When direct reclaim is observed it usually indicates a rapid
+ * increase in memory pressure. This occurs because the kswapd
+ * threads were unable to asynchronously keep enough free memory
+ * available. In this case set arc_no_grow to briefly pause arc
+ * growth to avoid compounding the memory pressure.
+ */
if (current_is_kswapd()) {
- strategy = ARC_RECLAIM_CONS;
- ARCSTAT_INCR(arcstat_memory_indirect_count, 1);
+ ARCSTAT_BUMP(arcstat_memory_indirect_count);
} else {
- strategy = ARC_RECLAIM_AGGR;
- ARCSTAT_INCR(arcstat_memory_direct_count, 1);
+ arc_no_grow = B_TRUE;
+ arc_grow_time = ddi_get_lbolt() + (arc_grow_retry * hz);
+ ARCSTAT_BUMP(arcstat_memory_direct_count);
}
- arc_kmem_reap_now(strategy);
- arc_reclaim = MAX(btop(((int64_t)arc_size - (int64_t)arc_c_min))
- >> arc_shrink_shift, 0);
mutex_exit(&arc_reclaim_thr_lock);
- return (arc_reclaim);
+ return (pages);
}
SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
}
ASSERT((int64_t)arc_p >= 0);
- if (arc_reclaim_needed()) {
- cv_signal(&arc_reclaim_thr_cv);
- return;
- }
-
if (arc_no_grow)
return;
return (1);
#endif
- if (arc_reclaim_needed())
+ if (arc_no_grow)
return (1);
return (arc_size > arc_c);
arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
{
#ifdef _KERNEL
- uint64_t available_memory = ptob(freemem);
- static uint64_t page_load = 0;
- static uint64_t last_txg = 0;
+ uint64_t available_memory;
+ /* Easily reclaimable memory (free + inactive + arc-evictable) */
+ available_memory = ptob(spl_kmem_availrmem()) + arc_evictable_memory();
#if defined(__i386)
available_memory =
MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
#endif
- if (available_memory >= zfs_write_limit_max)
- return (0);
- if (txg > last_txg) {
- last_txg = txg;
- page_load = 0;
- }
- /*
- * If we are in pageout, we know that memory is already tight,
- * the arc is already going to be evicting, so we just want to
- * continue to let page writes occur as quickly as possible.
- */
- if (curproc == proc_pageout) {
- if (page_load > MAX(ptob(minfree), available_memory) / 4)
- return (ERESTART);
- /* Note: reserve is inflated, so we deflate */
- page_load += reserve / 8;
- return (0);
- } else if (page_load > 0 && arc_reclaim_needed()) {
- /* memory is low, delay before restarting */
+ if (available_memory <= zfs_write_limit_max) {
ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
return (EAGAIN);
}
- page_load = 0;
-
- if (arc_size > arc_c_min) {
- uint64_t evictable_memory =
- arc_mru->arcs_lsize[ARC_BUFC_DATA] +
- arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
- arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
- arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
- available_memory += MIN(evictable_memory, arc_size - arc_c_min);
- }
if (inflight_data > available_memory / 4) {
ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
kstat_install(arc_ksp);
}
- (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
+ (void) thread_create(NULL, 0, arc_adapt_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
arc_dead = FALSE;
/*
* Avoid contributing to memory pressure.
*/
- if (arc_reclaim_needed()) {
+ if (arc_no_grow) {
ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
git://git.camperquake.de / zfs.git / commitdiff