Initial import from vendor-sys branch of openzfs

1 files changed, 465 insertions, 0 deletions

diff --git a/sys/contrib/openzfs/module/os/linux/zfs/arc_os.c b/sys/contrib/openzfs/module/os/linux/zfs/arc_os.c
new file mode 100644
index 000000000000..92f9bae8ccd3
--- /dev/null
+++ b/sys/contrib/openzfs/module/os/linux/zfs/arc_os.c
@@ -0,0 +1,465 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, Joyent, Inc.
+ * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
+ * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
+ */
+
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/spa_impl.h>
+#include <sys/zio_compress.h>
+#include <sys/zio_checksum.h>
+#include <sys/zfs_context.h>
+#include <sys/arc.h>
+#include <sys/zfs_refcount.h>
+#include <sys/vdev.h>
+#include <sys/vdev_trim.h>
+#include <sys/vdev_impl.h>
+#include <sys/dsl_pool.h>
+#include <sys/zio_checksum.h>
+#include <sys/multilist.h>
+#include <sys/abd.h>
+#include <sys/zil.h>
+#include <sys/fm/fs/zfs.h>
+#ifdef _KERNEL
+#include <sys/shrinker.h>
+#include <sys/vmsystm.h>
+#include <sys/zpl.h>
+#include <linux/page_compat.h>
+#endif
+#include <sys/callb.h>
+#include <sys/kstat.h>
+#include <sys/zthr.h>
+#include <zfs_fletcher.h>
+#include <sys/arc_impl.h>
+#include <sys/trace_zfs.h>
+#include <sys/aggsum.h>
+
+/*
+ * This is a limit on how many pages the ARC shrinker makes available for
+ * eviction in response to one page allocation attempt.  Note that in
+ * practice, the kernel's shrinker can ask us to evict up to about 4x this
+ * for one allocation attempt.
+ *
+ * The default limit of 10,000 (in practice, 160MB per allocation attempt
+ * with 4K pages) limits the amount of time spent attempting to reclaim ARC
+ * memory to less than 100ms per allocation attempt, even with a small
+ * average compressed block size of ~8KB.
+ *
+ * See also the comment in arc_shrinker_count().
+ * Set to 0 to disable limit.
+ */
+int zfs_arc_shrinker_limit = 10000;
+
+
+/*
+ * Return a default max arc size based on the amount of physical memory.
+ */
+uint64_t
+arc_default_max(uint64_t min, uint64_t allmem)
+{
+	/* Default to 1/2 of all memory. */
+	return (MAX(allmem / 2, min));
+}
+
+#ifdef _KERNEL
+/*
+ * Return maximum amount of memory that we could possibly use.  Reduced
+ * to half of all memory in user space which is primarily used for testing.
+ */
+uint64_t
+arc_all_memory(void)
+{
+#ifdef CONFIG_HIGHMEM
+	return (ptob(zfs_totalram_pages - zfs_totalhigh_pages));
+#else
+	return (ptob(zfs_totalram_pages));
+#endif /* CONFIG_HIGHMEM */
+}
+
+/*
+ * Return the amount of memory that is considered free.  In user space
+ * which is primarily used for testing we pretend that free memory ranges
+ * from 0-20% of all memory.
+ */
+uint64_t
+arc_free_memory(void)
+{
+#ifdef CONFIG_HIGHMEM
+	struct sysinfo si;
+	si_meminfo(&si);
+	return (ptob(si.freeram - si.freehigh));
+#else
+	return (ptob(nr_free_pages() +
+	    nr_inactive_file_pages() +
+	    nr_slab_reclaimable_pages()));
+#endif /* CONFIG_HIGHMEM */
+}
+
+/*
+ * Return the amount of memory that can be consumed before reclaim will be
+ * needed.  Positive if there is sufficient free memory, negative indicates
+ * the amount of memory that needs to be freed up.
+ */
+int64_t
+arc_available_memory(void)
+{
+	return (arc_free_memory() - arc_sys_free);
+}
+
+static uint64_t
+arc_evictable_memory(void)
+{
+	int64_t asize = aggsum_value(&arc_size);
+	uint64_t arc_clean =
+	    zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_DATA]) +
+	    zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_METADATA]) +
+	    zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_DATA]) +
+	    zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
+	uint64_t arc_dirty = MAX((int64_t)asize - (int64_t)arc_clean, 0);
+
+	/*
+	 * Scale reported evictable memory in proportion to page cache, cap
+	 * at specified min/max.
+	 */
+	uint64_t min = (ptob(nr_file_pages()) / 100) * zfs_arc_pc_percent;
+	min = MAX(arc_c_min, MIN(arc_c_max, min));
+
+	if (arc_dirty >= min)
+		return (arc_clean);
+
+	return (MAX((int64_t)asize - (int64_t)min, 0));
+}
+
+/*
+ * The _count() function returns the number of free-able objects.
+ * The _scan() function returns the number of objects that were freed.
+ */
+static unsigned long
+arc_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	/*
+	 * __GFP_FS won't be set if we are called from ZFS code (see
+	 * kmem_flags_convert(), which removes it).  To avoid a deadlock, we
+	 * don't allow evicting in this case.  We return 0 rather than
+	 * SHRINK_STOP so that the shrinker logic doesn't accumulate a
+	 * deficit against us.
+	 */
+	if (!(sc->gfp_mask & __GFP_FS)) {
+		return (0);
+	}
+
+	/*
+	 * This code is reached in the "direct reclaim" case, where the
+	 * kernel (outside ZFS) is trying to allocate a page, and the system
+	 * is low on memory.
+	 *
+	 * The kernel's shrinker code doesn't understand how many pages the
+	 * ARC's callback actually frees, so it may ask the ARC to shrink a
+	 * lot for one page allocation. This is problematic because it may
+	 * take a long time, thus delaying the page allocation, and because
+	 * it may force the ARC to unnecessarily shrink very small.
+	 *
+	 * Therefore, we limit the amount of data that we say is evictable,
+	 * which limits the amount that the shrinker will ask us to evict for
+	 * one page allocation attempt.
+	 *
+	 * In practice, we may be asked to shrink 4x the limit to satisfy one
+	 * page allocation, before the kernel's shrinker code gives up on us.
+	 * When that happens, we rely on the kernel code to find the pages
+	 * that we freed before invoking the OOM killer.  This happens in
+	 * __alloc_pages_slowpath(), which retries and finds the pages we
+	 * freed when it calls get_page_from_freelist().
+	 *
+	 * See also the comment above zfs_arc_shrinker_limit.
+	 */
+	int64_t limit = zfs_arc_shrinker_limit != 0 ?
+	    zfs_arc_shrinker_limit : INT64_MAX;
+	return (MIN(limit, btop((int64_t)arc_evictable_memory())));
+}
+
+static unsigned long
+arc_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+	ASSERT((sc->gfp_mask & __GFP_FS) != 0);
+
+	/* The arc is considered warm once reclaim has occurred */
+	if (unlikely(arc_warm == B_FALSE))
+		arc_warm = B_TRUE;
+
+	/*
+	 * Evict the requested number of pages by reducing arc_c and waiting
+	 * for the requested amount of data to be evicted.
+	 */
+	arc_reduce_target_size(ptob(sc->nr_to_scan));
+	arc_wait_for_eviction(ptob(sc->nr_to_scan));
+	if (current->reclaim_state != NULL)
+		current->reclaim_state->reclaimed_slab += sc->nr_to_scan;
+
+	/*
+	 * We are experiencing memory pressure which the arc_evict_zthr was
+	 * unable to keep up with. Set arc_no_grow to briefly pause arc
+	 * growth to avoid compounding the memory pressure.
+	 */
+	arc_no_grow = B_TRUE;
+
+	/*
+	 * 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.
+	 */
+	if (current_is_kswapd()) {
+		ARCSTAT_BUMP(arcstat_memory_indirect_count);
+	} else {
+		ARCSTAT_BUMP(arcstat_memory_direct_count);
+	}
+
+	return (sc->nr_to_scan);
+}
+
+SPL_SHRINKER_DECLARE(arc_shrinker,
+    arc_shrinker_count, arc_shrinker_scan, DEFAULT_SEEKS);
+
+int
+arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
+{
+	uint64_t free_memory = arc_free_memory();
+
+	if (free_memory > arc_all_memory() * arc_lotsfree_percent / 100)
+		return (0);
+
+	if (txg > spa->spa_lowmem_last_txg) {
+		spa->spa_lowmem_last_txg = txg;
+		spa->spa_lowmem_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 (current_is_kswapd()) {
+		if (spa->spa_lowmem_page_load >
+		    MAX(arc_sys_free / 4, free_memory) / 4) {
+			DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
+			return (SET_ERROR(ERESTART));
+		}
+		/* Note: reserve is inflated, so we deflate */
+		atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8);
+		return (0);
+	} else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) {
+		/* memory is low, delay before restarting */
+		ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
+		DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
+		return (SET_ERROR(EAGAIN));
+	}
+	spa->spa_lowmem_page_load = 0;
+	return (0);
+}
+
+void
+arc_lowmem_init(void)
+{
+	uint64_t allmem = arc_all_memory();
+
+	/*
+	 * 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);
+
+	/*
+	 * The ARC tries to keep at least this much memory available for the
+	 * system.  This gives the ARC time to shrink in response to memory
+	 * pressure, before running completely out of memory and invoking the
+	 * direct-reclaim ARC shrinker.
+	 *
+	 * This should be more than twice high_wmark_pages(), so that
+	 * arc_wait_for_eviction() will wait until at least the
+	 * high_wmark_pages() are free (see arc_evict_state_impl()).
+	 *
+	 * Note: Even when the system is very low on memory, the kernel's
+	 * shrinker code may only ask for one "batch" of pages (512KB) to be
+	 * evicted.  If concurrent allocations consume these pages, there may
+	 * still be insufficient free pages, and the OOM killer takes action.
+	 *
+	 * By setting arc_sys_free large enough, and having
+	 * arc_wait_for_eviction() wait until there is at least arc_sys_free/2
+	 * free memory, it is much less likely that concurrent allocations can
+	 * consume all the memory that was evicted before checking for
+	 * OOM.
+	 *
+	 * It's hard to iterate the zones from a linux kernel module, which
+	 * makes it difficult to determine the watermark dynamically. Instead
+	 * we compute the maximum high watermark for this system, based
+	 * on the amount of memory, assuming default parameters on Linux kernel
+	 * 5.3.
+	 */
+
+	/*
+	 * Base wmark_low is 4 * the square root of Kbytes of RAM.
+	 */
+	long wmark = 4 * int_sqrt(allmem/1024) * 1024;
+
+	/*
+	 * Clamp to between 128K and 64MB.
+	 */
+	wmark = MAX(wmark, 128 * 1024);
+	wmark = MIN(wmark, 64 * 1024 * 1024);
+
+	/*
+	 * watermark_boost can increase the wmark by up to 150%.
+	 */
+	wmark += wmark * 150 / 100;
+
+	/*
+	 * arc_sys_free needs to be more than 2x the watermark, because
+	 * arc_wait_for_eviction() waits for half of arc_sys_free.  Bump this up
+	 * to 3x to ensure we're above it.
+	 */
+	arc_sys_free = wmark * 3 + allmem / 32;
+}
+
+void
+arc_lowmem_fini(void)
+{
+	spl_unregister_shrinker(&arc_shrinker);
+}
+
+int
+param_set_arc_long(const char *buf, zfs_kernel_param_t *kp)
+{
+	int error;
+
+	error = param_set_long(buf, kp);
+	if (error < 0)
+		return (SET_ERROR(error));
+
+	arc_tuning_update(B_TRUE);
+
+	return (0);
+}
+
+int
+param_set_arc_int(const char *buf, zfs_kernel_param_t *kp)
+{
+	int error;
+
+	error = param_set_int(buf, kp);
+	if (error < 0)
+		return (SET_ERROR(error));
+
+	arc_tuning_update(B_TRUE);
+
+	return (0);
+}
+#else /* _KERNEL */
+int64_t
+arc_available_memory(void)
+{
+	int64_t lowest = INT64_MAX;
+
+	/* Every 100 calls, free a small amount */
+	if (spa_get_random(100) == 0)
+		lowest = -1024;
+
+	return (lowest);
+}
+
+int
+arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
+{
+	return (0);
+}
+
+uint64_t
+arc_all_memory(void)
+{
+	return (ptob(physmem) / 2);
+}
+
+uint64_t
+arc_free_memory(void)
+{
+	return (spa_get_random(arc_all_memory() * 20 / 100));
+}
+#endif /* _KERNEL */
+
+/*
+ * Helper function for arc_prune_async() it is responsible for safely
+ * handling the execution of a registered arc_prune_func_t.
+ */
+static void
+arc_prune_task(void *ptr)
+{
+	arc_prune_t *ap = (arc_prune_t *)ptr;
+	arc_prune_func_t *func = ap->p_pfunc;
+
+	if (func != NULL)
+		func(ap->p_adjust, ap->p_private);
+
+	zfs_refcount_remove(&ap->p_refcnt, func);
+}
+
+/*
+ * Notify registered consumers they must drop holds on a portion of the ARC
+ * buffered they reference.  This provides a mechanism to ensure the ARC can
+ * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers.  This
+ * is analogous to dnlc_reduce_cache() but more generic.
+ *
+ * This operation is performed asynchronously so it may be safely called
+ * in the context of the arc_reclaim_thread().  A reference is taken here
+ * for each registered arc_prune_t and the arc_prune_task() is responsible
+ * for releasing it once the registered arc_prune_func_t has completed.
+ */
+void
+arc_prune_async(int64_t adjust)
+{
+	arc_prune_t *ap;
+
+	mutex_enter(&arc_prune_mtx);
+	for (ap = list_head(&arc_prune_list); ap != NULL;
+	    ap = list_next(&arc_prune_list, ap)) {
+
+		if (zfs_refcount_count(&ap->p_refcnt) >= 2)
+			continue;
+
+		zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc);
+		ap->p_adjust = adjust;
+		if (taskq_dispatch(arc_prune_taskq, arc_prune_task,
+		    ap, TQ_SLEEP) == TASKQID_INVALID) {
+			zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc);
+			continue;
+		}
+		ARCSTAT_BUMP(arcstat_prune);
+	}
+	mutex_exit(&arc_prune_mtx);
+}
+
+/* BEGIN CSTYLED */
+ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, shrinker_limit, INT, ZMOD_RW,
+	"Limit on number of pages that ARC shrinker can reclaim at once");
+/* END CSTYLED */