mirror of https://github.com/openzfs/zfs.git
Reset l2ad_hand and l2ad_first in l2arc_evict
Increasing l2arc_write_size or l2arc_write_boost can result in l2arc_write_buffers() not having enough space to perform its writes and panic zio_write_phys(). Instead of resetting l2ad_hand to l2ad_start at the end of l2arc_write_buffers() and not taking into account a possible user-mediated increase of l2arc_write_max, we do this in l2arc_evict(), right after l2arc_write_size() has run. If there is not enough space to evict (ie we will exceed l2ad_end) we evict to the end of the device, reset l2ad_hand to l2ad_start, set l2ad_first to 0 and iterate l2arc_evict(). We avoid infinite iteration of l2arc_evict() by making sure in l2arc_write_size() that l2ad_start + size does not exceed l2ad_end. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #10154
This commit is contained in:
George Amanakis
GitHub
parent
c96a32e1a3
commit
37c22948e5
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@ -7467,9 +7467,9 @@ l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
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}
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static uint64_t
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l2arc_write_size(void)
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l2arc_write_size(l2arc_dev_t *dev)
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{
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uint64_t size;
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uint64_t size, dev_size;
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/*
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* Make sure our globals have meaningful values in case the user
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@ -7486,6 +7486,23 @@ l2arc_write_size(void)
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if (arc_warm == B_FALSE)
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size += l2arc_write_boost;
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/*
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* Make sure the write size does not exceed the size of the cache
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* device. This is important in l2arc_evict(), otherwise infinite
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* iteration can occur.
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*/
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dev_size = dev->l2ad_end - dev->l2ad_start;
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if (size >= dev_size) {
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cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
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"exceeds the size of the cache device (guid %llu), "
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"resetting them to the default (%d)",
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dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE);
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size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE;
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if (arc_warm == B_FALSE)
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size += l2arc_write_boost;
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}
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return (size);
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}
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@ -8008,22 +8025,22 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
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arc_buf_hdr_t *hdr, *hdr_prev;
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kmutex_t *hash_lock;
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uint64_t taddr;
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boolean_t rerun;
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buflist = &dev->l2ad_buflist;
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if (!all && dev->l2ad_first) {
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top:
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rerun = B_FALSE;
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if (dev->l2ad_hand >= (dev->l2ad_end - distance)) {
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/*
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* This is the first sweep through the device. There is
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* nothing to evict.
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*/
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return;
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}
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if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
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/*
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* When nearing the end of the device, evict to the end
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* before the device write hand jumps to the start.
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* When there is no space to accomodate upcoming writes,
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* evict to the end. Then bump the write hand to the start
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* and iterate. This iteration does not happen indefinitely
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* as we make sure in l2arc_write_size() that when l2ad_hand
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* is reset, the write size does not exceed the end of the
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* device.
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*/
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rerun = B_TRUE;
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taddr = dev->l2ad_end;
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} else {
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taddr = dev->l2ad_hand + distance;
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@ -8031,7 +8048,15 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
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DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
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uint64_t, taddr, boolean_t, all);
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top:
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if (!all && dev->l2ad_first) {
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/*
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* This is the first sweep through the device. There is
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* nothing to evict.
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*/
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goto out;
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}
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retry:
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mutex_enter(&dev->l2ad_mtx);
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for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
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hdr_prev = list_prev(buflist, hdr);
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@ -8052,7 +8077,7 @@ top:
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mutex_exit(&dev->l2ad_mtx);
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mutex_enter(hash_lock);
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mutex_exit(hash_lock);
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goto top;
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goto retry;
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}
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/*
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@ -8101,6 +8126,17 @@ top:
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mutex_exit(hash_lock);
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}
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mutex_exit(&dev->l2ad_mtx);
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out:
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if (rerun) {
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/*
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* Bump device hand to the device start if it is approaching the
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* end. l2arc_evict() has already evicted ahead for this case.
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*/
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dev->l2ad_hand = dev->l2ad_start;
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dev->l2ad_first = B_FALSE;
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goto top;
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}
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}
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/*
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@ -8448,15 +8484,6 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
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ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
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ARCSTAT_INCR(arcstat_l2_psize, write_psize);
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/*
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* Bump device hand to the device start if it is approaching the end.
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* l2arc_evict() will already have evicted ahead for this case.
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*/
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if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
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dev->l2ad_hand = dev->l2ad_start;
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dev->l2ad_first = B_FALSE;
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}
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dev->l2ad_writing = B_TRUE;
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(void) zio_wait(pio);
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dev->l2ad_writing = B_FALSE;
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@ -8539,7 +8566,7 @@ l2arc_feed_thread(void *unused)
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ARCSTAT_BUMP(arcstat_l2_feeds);
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size = l2arc_write_size();
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size = l2arc_write_size(dev);
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/*
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* Evict L2ARC buffers that will be overwritten.
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@ -49,7 +49,7 @@ post =
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[tests/functional/cache]
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tests = ['cache_001_pos', 'cache_002_pos', 'cache_003_pos', 'cache_004_neg',
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'cache_005_neg', 'cache_006_pos', 'cache_007_neg', 'cache_008_neg',
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'cache_009_pos', 'cache_010_neg', 'cache_011_pos']
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'cache_009_pos', 'cache_010_neg', 'cache_011_pos', 'cache_012_pos']
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tags = ['functional', 'cache']
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[tests/functional/cachefile]
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@ -4053,3 +4053,16 @@ function ls_xattr # path
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;;
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esac
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}
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function get_arcstat # stat
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{
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if is_linux; then
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typeset stat=$1
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typeset zfs_arcstats="/proc/spl/kstat/zfs/arcstats"
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[[ -f "$zfs_arcstats" ]] || return 1
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grep $stat $zfs_arcstats | awk '{print $3}'
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return $?
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else
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return 1
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fi
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}
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@ -35,6 +35,9 @@ DISABLE_IVSET_GUID_CHECK disable_ivset_guid_check zfs_disable_ivset_guid_check
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INITIALIZE_CHUNK_SIZE initialize_chunk_size zfs_initialize_chunk_size
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INITIALIZE_VALUE initialize_value zfs_initialize_value
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KEEP_LOG_SPACEMAPS_AT_EXPORT keep_log_spacemaps_at_export zfs_keep_log_spacemaps_at_export
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L2ARC_NOPREFETCH l2arc.noprefetch l2arc_noprefetch
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L2ARC_WRITE_BOOST l2arc.write_boost l2arc_write_boost
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L2ARC_WRITE_MAX l2arc.write_max l2arc_write_max
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LIVELIST_CONDENSE_NEW_ALLOC livelist.condense.new_alloc zfs_livelist_condense_new_alloc
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LIVELIST_CONDENSE_SYNC_CANCEL livelist.condense.sync_cancel zfs_livelist_condense_sync_cancel
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LIVELIST_CONDENSE_SYNC_PAUSE livelist.condense.sync_pause zfs_livelist_condense_sync_pause
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@ -12,7 +12,8 @@ dist_pkgdata_SCRIPTS = \
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cache_008_neg.ksh \
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cache_009_pos.ksh \
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cache_010_neg.ksh \
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cache_011_pos.ksh
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cache_011_pos.ksh \
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cache_012_pos.ksh
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dist_pkgdata_DATA = \
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cache.cfg \
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@ -0,0 +1,110 @@
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#!/bin/ksh -p
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#
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# CDDL HEADER START
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#
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# This file and its contents are supplied under the terms of the
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# Common Development and Distribution License ("CDDL"), version 1.0.
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# You may only use this file in accordance with the terms of version
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# 1.0 of the CDDL.
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#
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# A full copy of the text of the CDDL should have accompanied this
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# source. A copy of the CDDL is also available via the Internet at
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# http://www.illumos.org/license/CDDL.
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#
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# CDDL HEADER END
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#
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#
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# Copyright (c) 2020, George Amanakis. All rights reserved.
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#
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. $STF_SUITE/tests/functional/cache/cache.cfg
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. $STF_SUITE/tests/functional/cache/cache.kshlib
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#
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# DESCRIPTION:
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# Looping around a cache device with l2arc_write_size exceeding
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# the device size succeeds.
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#
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# STRATEGY:
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# 1. Create pool with a cache device.
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# 2. Set l2arc_write_max to a value larger than the cache device.
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# 3. Create a file larger than the cache device and random read
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# for 10 sec.
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# 4. Verify that l2arc_write_max is set back to the default.
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# 5. Set l2arc_write_max to a value less than the cache device size but
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# larger than the default (64MB).
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# 6. Record the l2_size.
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# 7. Random read for 1 sec.
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# 8. Record the l2_size again.
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# 9. If (6) <= (8) then we have not looped around yet.
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# 10. If (6) > (8) then we looped around. Break out of the loop and test.
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# 11. Destroy pool.
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#
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verify_runnable "global"
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log_assert "Looping around a cache device succeeds."
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function cleanup
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{
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if poolexists $TESTPOOL ; then
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destroy_pool $TESTPOOL
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fi
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log_must set_tunable32 L2ARC_WRITE_MAX $write_max
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log_must set_tunable32 L2ARC_NOPREFETCH $noprefetch
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}
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log_onexit cleanup
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typeset write_max=$(get_tunable L2ARC_WRITE_MAX)
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typeset noprefetch=$(get_tunable L2ARC_NOPREFETCH)
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log_must set_tunable32 L2ARC_NOPREFETCH 0
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typeset VDEV="$VDIR/vdev.disk"
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typeset VDEV_SZ=$(( 4 * 1024 * 1024 * 1024 ))
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typeset VCACHE="$VDIR/vdev.cache"
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typeset VCACHE_SZ=$(( $VDEV_SZ / 2 ))
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typeset fill_mb=$(( floor($VDEV_SZ * 3 / 4 ) ))
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export DIRECTORY=/$TESTPOOL
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export NUMJOBS=4
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export RUNTIME=10
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export PERF_RANDSEED=1234
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export PERF_COMPPERCENT=66
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export PERF_COMPCHUNK=0
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export BLOCKSIZE=128K
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export SYNC_TYPE=0
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export DIRECT=1
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export FILE_SIZE=$(( floor($fill_mb / $NUMJOBS) ))
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log_must set_tunable32 L2ARC_WRITE_MAX $(( $VCACHE_SZ * 2 ))
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log_must truncate -s $VCACHE_SZ $VCACHE
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log_must truncate -s $VDEV_SZ $VDEV
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log_must zpool create -f $TESTPOOL $VDEV cache $VCACHE
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log_must fio $FIO_SCRIPTS/mkfiles.fio
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log_must fio $FIO_SCRIPTS/random_reads.fio
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typeset write_max2=$(get_tunable L2ARC_WRITE_MAX)
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log_must test $write_max2 -eq $write_max
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log_must set_tunable32 L2ARC_WRITE_MAX $(( 64 * 1024 * 1024 ))
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export RUNTIME=1
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typeset do_once=true
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while $do_once || [[ $l2_size1 -le $l2_size2 ]]; do
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typeset l2_size1=$(get_arcstat l2_size)
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log_must fio $FIO_SCRIPTS/random_reads.fio
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typeset l2_size2=$(get_arcstat l2_size)
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do_once=false
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done
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log_must test $l2_size1 -gt $l2_size2
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log_must zpool destroy $TESTPOOL
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log_pass "Looping around a cache device succeeds."
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