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Add new kstat for monitoring time in dmu_tx_assign

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This change adds a new kstat to gain some visibility into the amount of
time spent in each call to dmu_tx_assign. A histogram is exported via
a new dmu_tx_assign_histogram-$POOLNAME file. The information contained
in this histogram is the frequency dmu_tx_assign took to complete given
an interval range. For example, given the below histogram file:

    $ cat /proc/spl/kstat/zfs/dmu_tx_assign_histogram-tank
    12 1 0x01 32 1536 19792068076691 20516481514522
    name                            type data
    1 us                            4    859
    2 us                            4    252
    4 us                            4    171
    8 us                            4    2
    16 us                           4    0
    32 us                           4    2
    64 us                           4    0
    128 us                          4    0
    256 us                          4    0
    512 us                          4    0
    1024 us                         4    0
    2048 us                         4    0
    4096 us                         4    0
    8192 us                         4    0
    16384 us                        4    0
    32768 us                        4    1
    65536 us                        4    1
    131072 us                       4    1
    262144 us                       4    4
    524288 us                       4    0
    1048576 us                      4    0
    2097152 us                      4    0
    4194304 us                      4    0
    8388608 us                      4    0
    16777216 us                     4    0
    33554432 us                     4    0
    67108864 us                     4    0
    134217728 us                    4    0
    268435456 us                    4    0
    536870912 us                    4    0
    1073741824 us                   4    0
    2147483648 us                   4    0

one can see most calls to dmu_tx_assign completed in 32us or less, but a
few outliers did not. Specifically, 4 of the calls took between 262144us
and 131072us. This information is difficult, if not impossible, to gather
without this change.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1584
This commit is contained in:
Prakash Surya
2013-07-10 15:53:48 -07:00
committed by Brian Behlendorf
parent bf89c19914
commit 92334b14ec
3 changed files with 72 additions and 0 deletions
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include/sys/dsl_pool.h
+5
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@@ -89,6 +89,7 @@ typedef struct dsl_pool {
uint64_t dp_root_dir_obj;
struct taskq *dp_iput_taskq;
kstat_t *dp_txg_kstat;
kstat_t *dp_tx_assign_kstat;
/* No lock needed - sync context only */
blkptr_t dp_meta_rootbp;
@@ -111,6 +112,8 @@ typedef struct dsl_pool {
uint64_t dp_mos_uncompressed_delta;
uint64_t dp_txg_history_size;
list_t dp_txg_history;
uint64_t dp_tx_assign_size;
kstat_named_t *dp_tx_assign_buckets;
/* Has its own locking */
@@ -162,6 +165,8 @@ extern int dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj,
extern void dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp);
int dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **);
void dsl_pool_tx_assign_add_usecs(dsl_pool_t *dp, uint64_t usecs);
txg_history_t *dsl_pool_txg_history_add(dsl_pool_t *dp, uint64_t txg);
txg_history_t *dsl_pool_txg_history_get(dsl_pool_t *dp, uint64_t txg);
void dsl_pool_txg_history_put(txg_history_t *th);