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zdb: add extra -T flag to show histograms of BRT refcounts 

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #16692
This commit is contained in:
Rob Norris 2024-11-02 03:08:33 +11:00 committed by GitHub
parent acb6e71eda
commit 673efbbf5d
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GPG Key ID: B5690EEEBB952194
2 changed files with 27 additions and 6 deletions
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29
cmd/zdb/zdb.c
View File

@ -2152,14 +2152,21 @@ dump_brt(spa_t *spa)
if (dump_opt['T'] < 3)
return;
/* -TTT shows a per-vdev histograms; -TTTT shows all entries */
boolean_t do_histo = dump_opt['T'] == 3;
char dva[64];
printf("\n%-16s %-10s\n", "DVA", "REFCNT");
if (!do_histo)
printf("\n%-16s %-10s\n", "DVA", "REFCNT");
for (uint64_t vdevid = 0; vdevid < brt->brt_nvdevs; vdevid++) {
brt_vdev_t *brtvd = &brt->brt_vdevs[vdevid];
if (brtvd == NULL || !brtvd->bv_initiated)
continue;
uint64_t counts[64] = {};
zap_cursor_t zc;
zap_attribute_t *za = zap_attribute_alloc();
for (zap_cursor_init(&zc, brt->brt_mos, brtvd->bv_mos_entries);
@ -2172,14 +2179,26 @@ dump_brt(spa_t *spa)
za->za_integer_length, za->za_num_integers,
&refcnt));
uint64_t offset = *(const uint64_t *)za->za_name;
if (do_histo)
counts[highbit64(refcnt)]++;
else {
uint64_t offset =
*(const uint64_t *)za->za_name;
snprintf(dva, sizeof (dva), "%" PRIu64 ":%llx", vdevid,
(u_longlong_t)offset);
printf("%-16s %-10llu\n", dva, (u_longlong_t)refcnt);
snprintf(dva, sizeof (dva), "%" PRIu64 ":%llx",
vdevid, (u_longlong_t)offset);
printf("%-16s %-10llu\n", dva,
(u_longlong_t)refcnt);
}
}
zap_cursor_fini(&zc);
zap_attribute_free(za);
if (do_histo) {
printf("\nBRT: vdev %" PRIu64
": DVAs with 2^n refcnts:\n", vdevid);
dump_histogram(counts, 64, 0);
}
}
}

4
man/man8/zdb.8
View File

@ -14,7 +14,7 @@
.\" Copyright (c) 2017 Lawrence Livermore National Security, LLC.
.\" Copyright (c) 2017 Intel Corporation.
.\"
.Dd November 18, 2023
.Dd October 27, 2024
.Dt ZDB 8
.Os
.
@ -408,6 +408,8 @@ blocks cloned, the space saving as a result of cloning, and the saving ratio.
.It Fl TT
Display the per-vdev BRT statistics, including total references.
.It Fl TTT
Display histograms of per-vdev BRT refcounts.
.It Fl TTTT
Dump the contents of the block reference tables.
.It Fl u , -uberblock
Display the current uberblock.