5376 arc_kmem_reap_now() should not result in clearing arc_no_grow
Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Steven Hartland <killing@multiplay.co.uk> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Author: Matthew Ahrens <mahrens@delphix.com> illumos/illumos-gate@2ec99e3e98
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@ -149,13 +149,7 @@ static kmutex_t arc_reclaim_thr_lock;
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static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
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static uint8_t arc_thread_exit;
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#define ARC_REDUCE_DNLC_PERCENT 3
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uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
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typedef enum arc_reclaim_strategy {
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ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
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ARC_RECLAIM_CONS /* Conservative reclaim strategy */
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} arc_reclaim_strategy_t;
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uint_t arc_reduce_dnlc_percent = 3;
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/*
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* The number of iterations through arc_evict_*() before we
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@ -170,7 +164,19 @@ static int arc_grow_retry = 60;
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static int arc_p_min_shift = 4;
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/* log2(fraction of arc to reclaim) */
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static int arc_shrink_shift = 5;
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static int arc_shrink_shift = 7;
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/*
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* log2(fraction of ARC which must be free to allow growing).
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* I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
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* when reading a new block into the ARC, we will evict an equal-sized block
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* from the ARC.
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*
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* This must be less than arc_shrink_shift, so that when we shrink the ARC,
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* we will still not allow it to grow.
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*/
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int arc_no_grow_shift = 5;
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/*
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* minimum lifespan of a prefetch block in clock ticks
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@ -2194,16 +2200,10 @@ arc_flush(spa_t *spa)
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}
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void
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arc_shrink(void)
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arc_shrink(int64_t to_free)
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{
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if (arc_c > arc_c_min) {
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uint64_t to_free;
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#ifdef _KERNEL
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to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
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#else
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to_free = arc_c >> arc_shrink_shift;
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#endif
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if (arc_c > arc_c_min + to_free)
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atomic_add_64(&arc_c, -to_free);
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else
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@ -2222,25 +2222,49 @@ arc_shrink(void)
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arc_adjust();
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}
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typedef enum free_memory_reason_t {
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FMR_UNKNOWN,
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FMR_NEEDFREE,
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FMR_LOTSFREE,
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FMR_SWAPFS_MINFREE,
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FMR_PAGES_PP_MAXIMUM,
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FMR_HEAP_ARENA,
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FMR_ZIO_ARENA,
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} free_memory_reason_t;
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int64_t last_free_memory;
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free_memory_reason_t last_free_reason;
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/*
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* Determine if the system is under memory pressure and is asking
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* to reclaim memory. A return value of 1 indicates that the system
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* is under memory pressure and that the arc should adjust accordingly.
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* Additional reserve of pages for pp_reserve.
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*/
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static int
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arc_reclaim_needed(void)
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int64_t arc_pages_pp_reserve = 64;
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/*
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* Additional reserve of pages for swapfs.
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*/
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int64_t arc_swapfs_reserve = 64;
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/*
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* Return the amount of memory that can be consumed before reclaim will be
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* needed. Positive if there is sufficient free memory, negative indicates
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* the amount of memory that needs to be freed up.
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*/
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static int64_t
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arc_available_memory(void)
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{
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uint64_t extra;
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int64_t lowest = INT64_MAX;
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int64_t n;
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free_memory_reason_t r = FMR_UNKNOWN;
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#ifdef _KERNEL
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if (needfree)
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return (1);
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/*
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* take 'desfree' extra pages, so we reclaim sooner, rather than later
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*/
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extra = desfree;
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if (needfree > 0) {
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n = PAGESIZE * (-needfree);
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if (n < lowest) {
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lowest = n;
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r = FMR_NEEDFREE;
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}
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}
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/*
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* check that we're out of range of the pageout scanner. It starts to
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@ -2249,8 +2273,11 @@ arc_reclaim_needed(void)
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* number of needed free pages. We add extra pages here to make sure
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* the scanner doesn't start up while we're freeing memory.
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*/
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if (freemem < lotsfree + needfree + extra)
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return (1);
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n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
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if (n < lowest) {
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lowest = n;
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r = FMR_LOTSFREE;
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}
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/*
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* check to make sure that swapfs has enough space so that anon
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@ -2259,8 +2286,13 @@ arc_reclaim_needed(void)
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* swap pages. We also add a bit of extra here just to prevent
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* circumstances from getting really dire.
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*/
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if (availrmem < swapfs_minfree + swapfs_reserve + extra)
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return (1);
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n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
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desfree - arc_swapfs_reserve);
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if (n < lowest) {
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lowest = n;
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r = FMR_SWAPFS_MINFREE;
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}
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/*
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* Check that we have enough availrmem that memory locking (e.g., via
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@ -2269,8 +2301,12 @@ arc_reclaim_needed(void)
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* drops below pages_pp_maximum, page locking mechanisms such as
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* page_pp_lock() will fail.)
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*/
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if (availrmem <= pages_pp_maximum)
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return (1);
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n = PAGESIZE * (availrmem - pages_pp_maximum -
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arc_pages_pp_reserve);
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if (n < lowest) {
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lowest = n;
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r = FMR_PAGES_PP_MAXIMUM;
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}
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#if defined(__i386)
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/*
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@ -2284,9 +2320,12 @@ arc_reclaim_needed(void)
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* heap is allocated. (Or, in the calculation, if less than 1/4th is
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* free)
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*/
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if (vmem_size(heap_arena, VMEM_FREE) <
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(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2))
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return (1);
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n = vmem_size(heap_arena, VMEM_FREE) -
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(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
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if (n < lowest) {
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lowest = n;
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r = FMR_HEAP_ARENA;
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}
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#endif
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/*
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@ -2298,19 +2337,40 @@ arc_reclaim_needed(void)
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* to aggressively evict memory from the arc in order to avoid
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* memory fragmentation issues.
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*/
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if (zio_arena != NULL &&
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vmem_size(zio_arena, VMEM_FREE) <
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(vmem_size(zio_arena, VMEM_ALLOC) >> 4))
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return (1);
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if (zio_arena != NULL) {
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n = vmem_size(zio_arena, VMEM_FREE) -
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(vmem_size(zio_arena, VMEM_ALLOC) >> 4);
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if (n < lowest) {
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lowest = n;
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r = FMR_ZIO_ARENA;
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}
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}
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#else
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/* Every 100 calls, free a small amount */
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if (spa_get_random(100) == 0)
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return (1);
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lowest = -1024;
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#endif
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return (0);
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last_free_memory = lowest;
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last_free_reason = r;
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return (lowest);
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}
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/*
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* Determine if the system is under memory pressure and is asking
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* to reclaim memory. A return value of TRUE indicates that the system
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* is under memory pressure and that the arc should adjust accordingly.
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*/
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static boolean_t
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arc_reclaim_needed(void)
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{
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return (arc_available_memory() < 0);
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}
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static void
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arc_kmem_reap_now(arc_reclaim_strategy_t strat)
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arc_kmem_reap_now(void)
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{
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size_t i;
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kmem_cache_t *prev_cache = NULL;
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@ -2335,13 +2395,6 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat)
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#endif
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#endif
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/*
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* An aggressive reclamation will shrink the cache size as well as
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* reap free buffers from the arc kmem caches.
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*/
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if (strat == ARC_RECLAIM_AGGR)
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arc_shrink();
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for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
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if (zio_buf_cache[i] != prev_cache) {
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prev_cache = zio_buf_cache[i];
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@ -2356,47 +2409,57 @@ arc_kmem_reap_now(arc_reclaim_strategy_t strat)
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kmem_cache_reap_now(hdr_cache);
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kmem_cache_reap_now(range_seg_cache);
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/*
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* Ask the vmem areana to reclaim unused memory from its
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* quantum caches.
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*/
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if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
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if (zio_arena != NULL) {
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/*
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* Ask the vmem arena to reclaim unused memory from its
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* quantum caches.
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*/
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vmem_qcache_reap(zio_arena);
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}
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}
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static void
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arc_reclaim_thread(void)
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{
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clock_t growtime = 0;
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arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
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callb_cpr_t cpr;
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CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
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mutex_enter(&arc_reclaim_thr_lock);
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while (arc_thread_exit == 0) {
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if (arc_reclaim_needed()) {
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int64_t free_memory = arc_available_memory();
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if (free_memory < 0) {
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if (arc_no_grow) {
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if (last_reclaim == ARC_RECLAIM_CONS) {
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last_reclaim = ARC_RECLAIM_AGGR;
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} else {
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last_reclaim = ARC_RECLAIM_CONS;
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}
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} else {
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arc_no_grow = TRUE;
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last_reclaim = ARC_RECLAIM_AGGR;
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membar_producer();
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}
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/* reset the growth delay for every reclaim */
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growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
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arc_kmem_reap_now(last_reclaim);
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arc_no_grow = B_TRUE;
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arc_warm = B_TRUE;
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} else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
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arc_no_grow = FALSE;
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/*
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* Wait at least zfs_grow_retry (default 60) seconds
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* before considering growing.
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*/
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growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
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arc_kmem_reap_now();
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/*
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* If we are still low on memory, shrink the ARC
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* so that we have arc_shrink_min free space.
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*/
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free_memory = arc_available_memory();
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int64_t to_free =
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(arc_c >> arc_shrink_shift) - free_memory;
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if (to_free > 0) {
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#ifdef _KERNEL
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to_free = MAX(to_free, ptob(needfree));
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#endif
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arc_shrink(to_free);
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}
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} else if (free_memory < arc_c >> arc_no_grow_shift) {
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arc_no_grow = B_TRUE;
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} else if (ddi_get_lbolt() >= growtime) {
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arc_no_grow = B_FALSE;
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}
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arc_adjust();
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@ -3739,6 +3802,15 @@ arc_tempreserve_space(uint64_t reserve, uint64_t txg)
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void
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arc_init(void)
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{
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/*
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* allmem is "all memory that we could possibly use".
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*/
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#ifdef _KERNEL
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uint64_t allmem = ptob(physmem - swapfs_minfree);
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#else
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uint64_t allmem = (physmem * PAGESIZE) / 2;
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#endif
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mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
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cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
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@ -3746,7 +3818,7 @@ arc_init(void)
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arc_min_prefetch_lifespan = 1 * hz;
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/* Start out with 1/8 of all memory */
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arc_c = physmem * PAGESIZE / 8;
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arc_c = allmem / 8;
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#ifdef _KERNEL
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/*
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@ -3758,21 +3830,21 @@ arc_init(void)
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#endif
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/* set min cache to 1/32 of all memory, or 64MB, whichever is more */
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arc_c_min = MAX(arc_c / 4, 64<<20);
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arc_c_min = MAX(allmem / 32, 64 << 20);
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/* set max to 3/4 of all memory, or all but 1GB, whichever is more */
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if (arc_c * 8 >= 1<<30)
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arc_c_max = (arc_c * 8) - (1<<30);
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if (allmem >= 1 << 30)
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arc_c_max = allmem - (1 << 30);
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else
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arc_c_max = arc_c_min;
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arc_c_max = MAX(arc_c * 6, arc_c_max);
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arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
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/*
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* Allow the tunables to override our calculations if they are
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* reasonable (ie. over 64MB)
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*/
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if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
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if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem)
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arc_c_max = zfs_arc_max;
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if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
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if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
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arc_c_min = zfs_arc_min;
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arc_c = arc_c_max;
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@ -3800,6 +3872,12 @@ arc_init(void)
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if (zfs_arc_shrink_shift > 0)
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arc_shrink_shift = zfs_arc_shrink_shift;
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/*
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* Ensure that arc_no_grow_shift is less than arc_shrink_shift.
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*/
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if (arc_no_grow_shift >= arc_shrink_shift)
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arc_no_grow_shift = arc_shrink_shift - 1;
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if (zfs_arc_p_min_shift > 0)
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arc_p_min_shift = zfs_arc_p_min_shift;
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