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expose free space histograms in /proc 

example output:
```
[root@nixos:~]# cat /proc/spl/kstat/zfs/vm/fragmentation
normal{power="9",pool="vm"} 14
normal{power="10",pool="vm"} 75
normal{power="11",pool="vm"} 16
normal{power="12",pool="vm"} 37
```

this allows graphing `zdb -MM` without any performance costs

# Conflicts:
#	module/zfs/spa_stats.c
This commit is contained in:
Michael Bishop 2022-10-10 21:37:27 -03:00
parent c0bd9caebe
commit bbec9ab76d
2 changed files with 67 additions and 0 deletions
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1
include/sys/spa.h
View File

@ -902,6 +902,7 @@ typedef struct spa_stats {
spa_history_kstat_t state; /* pool state */
spa_history_kstat_t guid; /* pool guid */
spa_history_kstat_t iostats;
spa_history_kstat_t fragmentation;
} spa_stats_t;
typedef enum txg_state {

66
module/zfs/spa_stats.c
View File

@ -24,6 +24,7 @@
#include <sys/vdev_impl.h>
#include <sys/spa.h>
#include <zfs_comutil.h>
#include <sys/metaslab_impl.h>
/*
* Keeps stats on last N reads per spa_t, disabled by default.
@ -302,6 +303,69 @@ spa_txg_history_init(spa_t *spa)
offsetof(spa_txg_history_t, sth_node));
}
static void *
spa_frag_addr(kstat_t *ksp, loff_t n)
{
if (n == 0)
return ksp->ks_private;
return NULL;
}
static int
spa_frag_data(char *buf, size_t size, void *data) {
spa_t *spa = (spa_t *)data;
size_t offset = 0;
const char *name = spa_name(spa);
metaslab_class_t *mc = spa_normal_class(spa);
for (int i=0; i<RANGE_TREE_HISTOGRAM_SIZE; i++) {
if (mc->mc_histogram[i] > 0) {
int res = snprintf(buf + offset, size, "zfs_fragmentation_normal{power=\"%d\",pool=\"%s\"} %llu\n", i, name, (u_longlong_t)mc->mc_histogram[i]);
offset += res;
size -= res;
}
}
metaslab_class_t *smc = spa_special_class(spa);
for (int i=0; i<RANGE_TREE_HISTOGRAM_SIZE; i++) {
if (smc->mc_histogram[i] > 0) {
int res = snprintf(buf + offset, size, "zfs_fragmentation_special{power=\"%d\",pool=\"%s\"} %llu\n", i, name, (u_longlong_t)smc->mc_histogram[i]);
offset += res;
size -= res;
}
}
return 0;
}
static void
spa_fragmentation_init(spa_t *spa)
{
char *name;
spa_history_kstat_t *shk = &spa->spa_stats.fragmentation;
kstat_t *ksp;
name = kmem_asprintf("zfs/%s", spa_name(spa));
ksp = kstat_create(name, 0, "fragmentation", "misc", KSTAT_TYPE_RAW, 0, KSTAT_FLAG_VIRTUAL);
shk->kstat = ksp;
if (ksp) {
ksp->ks_private = spa;
ksp->ks_flags |= KSTAT_FLAG_NO_HEADERS;
kstat_set_raw_ops(ksp, NULL, spa_frag_data, spa_frag_addr);
kstat_install(ksp);
}
kmem_strfree(name);
}
static void
spa_fragmentation_destroy(spa_t *spa)
{
spa_history_kstat_t *shk = &spa->spa_stats.fragmentation;
kstat_t *ksp = shk->kstat;
if (ksp)
kstat_delete(ksp);
}
static void
spa_txg_history_destroy(spa_t *spa)
{
@ -998,11 +1062,13 @@ spa_stats_init(spa_t *spa)
spa_state_init(spa);
spa_guid_init(spa);
spa_iostats_init(spa);
spa_fragmentation_init(spa);
}
void
spa_stats_destroy(spa_t *spa)
{
spa_fragmentation_destroy(spa);
spa_iostats_destroy(spa);
spa_guid_destroy(spa);
spa_state_destroy(spa);