diff --git a/module/zfs/arc.c b/module/zfs/arc.c index cbc27d368..d6eaa6cf0 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -158,7 +158,10 @@ typedef enum arc_reclaim_strategy { } 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; @@ -909,21 +912,6 @@ buf_dest(void *vbuf, void *unused) 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) { @@ -956,7 +944,7 @@ retry: } 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); @@ -2101,16 +2089,13 @@ arc_flush(spa_t *spa) } 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 @@ -2129,66 +2114,8 @@ arc_shrink(void) 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; @@ -2201,7 +2128,7 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat) * 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) { @@ -2218,11 +2145,16 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat) 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; @@ -2230,7 +2162,10 @@ arc_reclaim_thread(void) 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) { @@ -2245,14 +2180,16 @@ arc_reclaim_thread(void) } /* 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; - - } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { - arc_no_grow = FALSE; } +#endif /* !_KERNEL */ + + /* 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 @@ -2283,28 +2220,83 @@ arc_reclaim_thread(void) #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); + /* The arc is considered warm once reclaim has occurred */ + if (unlikely(arc_warm == B_FALSE)) + arc_warm = B_TRUE; + + /* Return the potential number of reclaimable pages */ + pages = btop(arc_evictable_memory()); if (sc->nr_to_scan == 0) - return (arc_reclaim); - - /* Prevent reclaim below arc_c_min */ - if (arc_reclaim <= 0) - return (-1); + return (pages); /* Not allowed to perform filesystem reclaim */ if (!(sc->gfp_mask & __GFP_FS)) @@ -2314,20 +2306,37 @@ __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc) 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); + /* + * 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 { - strategy = ARC_RECLAIM_AGGR; - ARCSTAT_INCR(arcstat_memory_direct_count, 1); + 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()) { + ARCSTAT_BUMP(arcstat_memory_indirect_count); + } else { + 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); @@ -2375,11 +2384,6 @@ arc_adapt(int bytes, arc_state_t *state) } ASSERT((int64_t)arc_p >= 0); - if (arc_reclaim_needed()) { - cv_signal(&arc_reclaim_thr_cv); - return; - } - if (arc_no_grow) return; @@ -2424,7 +2428,7 @@ arc_evict_needed(arc_buf_contents_t type) return (1); #endif - if (arc_reclaim_needed()) + if (arc_no_grow) return (1); return (arc_size > arc_c); @@ -3557,48 +3561,20 @@ static int 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); @@ -3850,7 +3826,7 @@ arc_init(void) 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; @@ -4775,7 +4751,7 @@ l2arc_feed_thread(void) /* * 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;