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Persistent L2ARC
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This commit makes the L2ARC persistent across reboots. We implement
a light-weight persistent L2ARC metadata structure that allows L2ARC
contents to be recovered after a reboot. This significantly eases the
impact a reboot has on read performance on systems with large caches.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Saso Kiselkov <skiselkov@gmail.com>
Co-authored-by: Jorgen Lundman <lundman@lundman.net>
Co-authored-by: George Amanakis <gamanakis@gmail.com>
Ported-by: Yuxuan Shui <yshuiv7@gmail.com>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes openzfs#925 
Closes openzfs#1823 
Closes openzfs#2672 
Closes openzfs#3744 
Closes openzfs#9582
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@gamanakis
gamanakis authored Apr 10, 2020
1 parent 36a6e23 commit 77f6826
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Showing 30 changed files with 3,020 additions and 88 deletions.
229 changes: 228 additions & 1 deletion cmd/zdb/zdb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,7 @@
#include <sys/zio_compress.h>
#include <sys/zfs_fuid.h>
#include <sys/arc.h>
#include <sys/arc_impl.h>
#include <sys/ddt.h>
#include <sys/zfeature.h>
#include <sys/abd.h>
Expand Down Expand Up @@ -3474,6 +3475,216 @@ print_label_header(zdb_label_t *label, int l)
label->header_printed = B_TRUE;
}

static void
print_l2arc_header(void)
{
(void) printf("------------------------------------\n");
(void) printf("L2ARC device header\n");
(void) printf("------------------------------------\n");
}

static void
print_l2arc_log_blocks(void)
{
(void) printf("------------------------------------\n");
(void) printf("L2ARC device log blocks\n");
(void) printf("------------------------------------\n");
}

static void
dump_l2arc_log_entries(uint64_t log_entries,
l2arc_log_ent_phys_t *le, int i)
{
for (int j = 0; j < log_entries; j++) {
dva_t dva = le[j].le_dva;
(void) printf("lb[%4d]\tle[%4d]\tDVA asize: %llu, "
"vdev: %llu, offset: %llu\n", i, j + 1,
(u_longlong_t)DVA_GET_ASIZE(&dva),
(u_longlong_t)DVA_GET_VDEV(&dva),
(u_longlong_t)DVA_GET_OFFSET(&dva));
(void) printf("|\t\t\t\tbirth: %llu\n",
(u_longlong_t)le[j].le_birth);
(void) printf("|\t\t\t\tlsize: %llu\n",
(u_longlong_t)L2BLK_GET_LSIZE((&le[j])->le_prop));
(void) printf("|\t\t\t\tpsize: %llu\n",
(u_longlong_t)L2BLK_GET_PSIZE((&le[j])->le_prop));
(void) printf("|\t\t\t\tcompr: %llu\n",
(u_longlong_t)L2BLK_GET_COMPRESS((&le[j])->le_prop));
(void) printf("|\t\t\t\ttype: %llu\n",
(u_longlong_t)L2BLK_GET_TYPE((&le[j])->le_prop));
(void) printf("|\t\t\t\tprotected: %llu\n",
(u_longlong_t)L2BLK_GET_PROTECTED((&le[j])->le_prop));
(void) printf("|\t\t\t\tprefetch: %llu\n",
(u_longlong_t)L2BLK_GET_PREFETCH((&le[j])->le_prop));
(void) printf("|\t\t\t\taddress: %llu\n",
(u_longlong_t)le[j].le_daddr);
(void) printf("|\n");
}
(void) printf("\n");
}

static void
dump_l2arc_log_blkptr(l2arc_log_blkptr_t lbps)
{
(void) printf("|\t\tdaddr: %llu\n", (u_longlong_t)lbps.lbp_daddr);
(void) printf("|\t\tpayload_asize: %llu\n",
(u_longlong_t)lbps.lbp_payload_asize);
(void) printf("|\t\tpayload_start: %llu\n",
(u_longlong_t)lbps.lbp_payload_start);
(void) printf("|\t\tlsize: %llu\n",
(u_longlong_t)L2BLK_GET_LSIZE((&lbps)->lbp_prop));
(void) printf("|\t\tpsize: %llu\n",
(u_longlong_t)L2BLK_GET_PSIZE((&lbps)->lbp_prop));
(void) printf("|\t\tcompralgo: %llu\n",
(u_longlong_t)L2BLK_GET_COMPRESS((&lbps)->lbp_prop));
(void) printf("|\t\tcksumalgo: %llu\n",
(u_longlong_t)L2BLK_GET_CHECKSUM((&lbps)->lbp_prop));
(void) printf("|\n\n");
}

static void
dump_l2arc_log_blocks(int fd, l2arc_dev_hdr_phys_t l2dhdr)
{
l2arc_log_blk_phys_t this_lb;
uint64_t psize;
l2arc_log_blkptr_t lbps[2];
abd_t *abd;
zio_cksum_t cksum;
int i = 0, failed = 0;
l2arc_dev_t dev;

print_l2arc_log_blocks();
bcopy((&l2dhdr)->dh_start_lbps, lbps, sizeof (lbps));

dev.l2ad_evict = l2dhdr.dh_evict;
dev.l2ad_start = l2dhdr.dh_start;
dev.l2ad_end = l2dhdr.dh_end;

if (l2dhdr.dh_start_lbps[0].lbp_daddr == 0) {
/* no log blocks to read */
(void) printf("No log blocks to read\n");
(void) printf("\n");
return;
} else {
dev.l2ad_hand = lbps[0].lbp_daddr +
L2BLK_GET_PSIZE((&lbps[0])->lbp_prop);
}

dev.l2ad_first = !!(l2dhdr.dh_flags & L2ARC_DEV_HDR_EVICT_FIRST);

for (;;) {
if (!l2arc_log_blkptr_valid(&dev, &lbps[0]))
break;

psize = L2BLK_GET_PSIZE((&lbps[0])->lbp_prop);
if (pread64(fd, &this_lb, psize, lbps[0].lbp_daddr) != psize) {
(void) printf("Error while reading next log block\n\n");
break;
}

fletcher_4_native_varsize(&this_lb, psize, &cksum);
if (!ZIO_CHECKSUM_EQUAL(cksum, lbps[0].lbp_cksum)) {
failed++;
(void) printf("Invalid cksum\n");
dump_l2arc_log_blkptr(lbps[0]);
break;
}

switch (L2BLK_GET_COMPRESS((&lbps[0])->lbp_prop)) {
case ZIO_COMPRESS_OFF:
break;
case ZIO_COMPRESS_LZ4:
abd = abd_alloc_for_io(psize, B_TRUE);
abd_copy_from_buf_off(abd, &this_lb, 0, psize);
zio_decompress_data(L2BLK_GET_COMPRESS(
(&lbps[0])->lbp_prop), abd, &this_lb,
psize, sizeof (this_lb));
abd_free(abd);
break;
default:
break;
}

if (this_lb.lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC))
byteswap_uint64_array(&this_lb, psize);

if (this_lb.lb_magic != L2ARC_LOG_BLK_MAGIC) {
(void) printf("Invalid log block magic\n\n");
break;
}

i++;
if (dump_opt['l'] > 1) {
(void) printf("lb[%4d]\tmagic: %llu\n", i,
(u_longlong_t)this_lb.lb_magic);
dump_l2arc_log_blkptr(lbps[0]);
}

if (dump_opt['l'] > 2)
dump_l2arc_log_entries(l2dhdr.dh_log_blk_ent,
this_lb.lb_entries, i);

if (l2arc_range_check_overlap(lbps[1].lbp_daddr,
lbps[0].lbp_daddr, dev.l2ad_evict) && !dev.l2ad_first)
break;

lbps[0] = lbps[1];
lbps[1] = this_lb.lb_prev_lbp;
}

(void) printf("log_blk_count:\t %d with valid cksum\n", i);
(void) printf("\t\t %d with invalid cksum\n\n", failed);
}

static void
dump_l2arc_header(int fd)
{
l2arc_dev_hdr_phys_t l2dhdr;
int error = B_FALSE;

if (pread64(fd, &l2dhdr, sizeof (l2dhdr),
VDEV_LABEL_START_SIZE) != sizeof (l2dhdr)) {
error = B_TRUE;
} else {
if (l2dhdr.dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC))
byteswap_uint64_array(&l2dhdr, sizeof (l2dhdr));

if (l2dhdr.dh_magic != L2ARC_DEV_HDR_MAGIC)
error = B_TRUE;
}

if (error) {
(void) printf("L2ARC device header not found\n\n");
} else if (!dump_opt['q']) {
print_l2arc_header();

(void) printf(" magic: %llu\n",
(u_longlong_t)l2dhdr.dh_magic);
(void) printf(" version: %llu\n",
(u_longlong_t)l2dhdr.dh_version);
(void) printf(" pool_guid: %llu\n",
(u_longlong_t)l2dhdr.dh_spa_guid);
(void) printf(" flags: %llu\n",
(u_longlong_t)l2dhdr.dh_flags);
(void) printf(" start_lbps[0]: %llu\n",
(u_longlong_t)
l2dhdr.dh_start_lbps[0].lbp_daddr);
(void) printf(" start_lbps[1]: %llu\n",
(u_longlong_t)
l2dhdr.dh_start_lbps[1].lbp_daddr);
(void) printf(" log_blk_ent: %llu\n",
(u_longlong_t)l2dhdr.dh_log_blk_ent);
(void) printf(" start: %llu\n",
(u_longlong_t)l2dhdr.dh_start);
(void) printf(" end: %llu\n",
(u_longlong_t)l2dhdr.dh_end);
(void) printf(" evict: %llu\n\n",
(u_longlong_t)l2dhdr.dh_evict);

dump_l2arc_log_blocks(fd, l2dhdr);
}
}

static void
dump_config_from_label(zdb_label_t *label, size_t buflen, int l)
{
Expand Down Expand Up @@ -3639,10 +3850,11 @@ dump_label(const char *dev)
{
char path[MAXPATHLEN];
zdb_label_t labels[VDEV_LABELS];
uint64_t psize, ashift;
uint64_t psize, ashift, l2cache;
struct stat64 statbuf;
boolean_t config_found = B_FALSE;
boolean_t error = B_FALSE;
boolean_t read_l2arc_header = B_FALSE;
avl_tree_t config_tree;
avl_tree_t uberblock_tree;
void *node, *cookie;
Expand Down Expand Up @@ -3735,6 +3947,15 @@ dump_label(const char *dev)
if (nvlist_size(config, &size, NV_ENCODE_XDR) != 0)
size = buflen;

/* If the device is a cache device clear the header. */
if (!read_l2arc_header) {
if (nvlist_lookup_uint64(config,
ZPOOL_CONFIG_POOL_STATE, &l2cache) == 0 &&
l2cache == POOL_STATE_L2CACHE) {
read_l2arc_header = B_TRUE;
}
}

fletcher_4_native_varsize(buf, size, &cksum);
rec = cksum_record_insert(&config_tree, &cksum, l);

Expand Down Expand Up @@ -3785,6 +4006,12 @@ dump_label(const char *dev)
nvlist_free(label->config_nv);
}

/*
* Dump the L2ARC header, if existent.
*/
if (read_l2arc_header)
dump_l2arc_header(fd);

cookie = NULL;
while ((node = avl_destroy_nodes(&config_tree, &cookie)) != NULL)
umem_free(node, sizeof (cksum_record_t));
Expand Down
1 change: 1 addition & 0 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -336,6 +336,7 @@ AC_CONFIG_FILES([
tests/zfs-tests/tests/functional/no_space/Makefile
tests/zfs-tests/tests/functional/nopwrite/Makefile
tests/zfs-tests/tests/functional/online_offline/Makefile
tests/zfs-tests/tests/functional/persist_l2arc/Makefile
tests/zfs-tests/tests/functional/pool_checkpoint/Makefile
tests/zfs-tests/tests/functional/pool_names/Makefile
tests/zfs-tests/tests/functional/poolversion/Makefile
Expand Down
4 changes: 4 additions & 0 deletions include/sys/arc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -310,10 +310,14 @@ void arc_fini(void);
void l2arc_add_vdev(spa_t *spa, vdev_t *vd);
void l2arc_remove_vdev(vdev_t *vd);
boolean_t l2arc_vdev_present(vdev_t *vd);
void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen);
boolean_t l2arc_range_check_overlap(uint64_t bottom, uint64_t top,
uint64_t check);
void l2arc_init(void);
void l2arc_fini(void);
void l2arc_start(void);
void l2arc_stop(void);
void l2arc_spa_rebuild_start(spa_t *spa);

#ifndef _KERNEL
extern boolean_t arc_watch;
Expand Down
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