From 090ff0929ec7a2e2e65efaaddb9981d15964f7d9 Mon Sep 17 00:00:00 2001 From: "Ricardo M. Correia" Date: Thu, 26 Aug 2010 10:17:18 -0700 Subject: [PATCH] Fix commit callbacks The upstream commit cb code had a few bugs: 1) The arguments of the list_move_tail() call in txg_dispatch_callbacks() were reversed by mistake. This caused the commit callbacks to not be called at all. 2) ztest had a bug in ztest_dmu_commit_callbacks() where "error" was not initialized correctly. This seems to have caused the test to always take the simulated error code path, which made ztest unable to detect whether commit cbs were being called for transactions that successfuly complete. 3) ztest had another bug in ztest_dmu_commit_callbacks() where the commit cb threshold was not being compared correctly. 4) The commit cb taskq was using 'max_ncpus * 2' as the maxalloc argument of taskq_create(), which could have caused unnecessary delays in the txg sync thread. Signed-off-by: Brian Behlendorf --- cmd/ztest/ztest.c | 47 ++++++++++++++++++++++++++++++++--------------- module/zfs/txg.c | 6 +++--- 2 files changed, 35 insertions(+), 18 deletions(-) diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c index ad73735581..b5cee5b3bd 100644 --- a/cmd/ztest/ztest.c +++ b/cmd/ztest/ztest.c @@ -341,6 +341,22 @@ static boolean_t ztest_exiting; /* Global commit callback list */ static ztest_cb_list_t zcl; +/* Commit cb delay */ +static uint64_t zc_min_txg_delay = UINT64_MAX; +static int zc_cb_counter = 0; + +/* + * Minimum number of commit callbacks that need to be registered for us to check + * whether the minimum txg delay is acceptable. + */ +#define ZTEST_COMMIT_CB_MIN_REG 100 + +/* + * If a number of txgs equal to this threshold have been created after a commit + * callback has been registered but not called, then we assume there is an + * implementation bug. + */ +#define ZTEST_COMMIT_CB_THRESH (TXG_CONCURRENT_STATES + 1000) extern uint64_t metaslab_gang_bang; extern uint64_t metaslab_df_alloc_threshold; @@ -4092,18 +4108,20 @@ ztest_commit_callback(void *arg, int error) return; } - /* Was this callback added to the global callback list? */ - if (!data->zcd_added) - goto out; - + ASSERT(data->zcd_added); ASSERT3U(data->zcd_txg, !=, 0); - /* Remove our callback from the list */ (void) mutex_lock(&zcl.zcl_callbacks_lock); + + /* See if this cb was called more quickly */ + if ((synced_txg - data->zcd_txg) < zc_min_txg_delay) + zc_min_txg_delay = synced_txg - data->zcd_txg; + + /* Remove our callback from the list */ list_remove(&zcl.zcl_callbacks, data); + (void) mutex_unlock(&zcl.zcl_callbacks_lock); -out: umem_free(data, sizeof (ztest_cb_data_t)); } @@ -4121,13 +4139,6 @@ ztest_create_cb_data(objset_t *os, uint64_t txg) return (cb_data); } -/* - * If a number of txgs equal to this threshold have been created after a commit - * callback has been registered but not called, then we assume there is an - * implementation bug. - */ -#define ZTEST_COMMIT_CALLBACK_THRESH (TXG_CONCURRENT_STATES + 2) - /* * Commit callback test. */ @@ -4139,7 +4150,7 @@ ztest_dmu_commit_callbacks(ztest_ds_t *zd, uint64_t id) dmu_tx_t *tx; ztest_cb_data_t *cb_data[3], *tmp_cb; uint64_t old_txg, txg; - int i, error; + int i, error = 0; ztest_od_init(&od[0], id, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0); @@ -4219,7 +4230,7 @@ ztest_dmu_commit_callbacks(ztest_ds_t *zd, uint64_t id) */ tmp_cb = list_head(&zcl.zcl_callbacks); if (tmp_cb != NULL && - tmp_cb->zcd_txg > txg - ZTEST_COMMIT_CALLBACK_THRESH) { + tmp_cb->zcd_txg + ZTEST_COMMIT_CB_THRESH < txg) { fatal(0, "Commit callback threshold exceeded, oldest txg: %" PRIu64 ", open txg: %" PRIu64 "\n", tmp_cb->zcd_txg, txg); } @@ -4250,6 +4261,8 @@ ztest_dmu_commit_callbacks(ztest_ds_t *zd, uint64_t id) tmp_cb = cb_data[i]; } + zc_cb_counter += 3; + (void) mutex_unlock(&zcl.zcl_callbacks_lock); dmu_tx_commit(tx); @@ -5256,6 +5269,10 @@ ztest_run(ztest_shared_t *zs) for (uint64_t object = 1; object < 50; object++) dmu_prefetch(spa->spa_meta_objset, object, 0, 1ULL << 20); + /* Verify that at least one commit cb was called in a timely fashion */ + if (zc_cb_counter >= ZTEST_COMMIT_CB_MIN_REG) + VERIFY3U(zc_min_txg_delay, ==, 0); + spa_close(spa, FTAG); /* diff --git a/module/zfs/txg.c b/module/zfs/txg.c index 9b308ca4e7..f9f24dd0a9 100644 --- a/module/zfs/txg.c +++ b/module/zfs/txg.c @@ -335,15 +335,15 @@ txg_dispatch_callbacks(dsl_pool_t *dp, uint64_t txg) * Commit callback taskq hasn't been created yet. */ tx->tx_commit_cb_taskq = taskq_create("tx_commit_cb", - max_ncpus, minclsyspri, max_ncpus, max_ncpus * 2, - TASKQ_PREPOPULATE); + 100, minclsyspri, max_ncpus, INT_MAX, + TASKQ_THREADS_CPU_PCT | TASKQ_PREPOPULATE); } cb_list = kmem_alloc(sizeof (list_t), KM_SLEEP); list_create(cb_list, sizeof (dmu_tx_callback_t), offsetof(dmu_tx_callback_t, dcb_node)); - list_move_tail(&tc->tc_callbacks[g], cb_list); + list_move_tail(cb_list, &tc->tc_callbacks[g]); (void) taskq_dispatch(tx->tx_commit_cb_taskq, (task_func_t *) txg_do_callbacks, cb_list, TQ_SLEEP);