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3740 Poor ZFS send / receive performance due to snapshot hold / release processing
Submitted by: Steven Hartland <steven.hartland@multiplay.co.uk>


 819         dsl_dataset_rele(ds, FTAG);
 820 }
 821 
 822 taskq_t *
 823 dsl_pool_vnrele_taskq(dsl_pool_t *dp)
 824 {
 825         return (dp->dp_vnrele_taskq);
 826 }
 827 
 828 /*
 829  * Walk through the pool-wide zap object of temporary snapshot user holds
 830  * and release them.
 831  */
 832 void
 833 dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp)
 834 {
 835         zap_attribute_t za;
 836         zap_cursor_t zc;
 837         objset_t *mos = dp->dp_meta_objset;
 838         uint64_t zapobj = dp->dp_tmp_userrefs_obj;

 839 
 840         if (zapobj == 0)
 841                 return;
 842         ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
 843 


 844         for (zap_cursor_init(&zc, mos, zapobj);
 845             zap_cursor_retrieve(&zc, &za) == 0;
 846             zap_cursor_advance(&zc)) {
 847                 char *htag;
 848                 uint64_t dsobj;

 849 
 850                 htag = strchr(za.za_name, '-');
 851                 *htag = '\0';
 852                 ++htag;
 853                 dsobj = strtonum(za.za_name, NULL);
 854                 dsl_dataset_user_release_tmp(dp, dsobj, htag);






 855         }


 856         zap_cursor_fini(&zc);
 857 }
 858 
 859 /*
 860  * Create the pool-wide zap object for storing temporary snapshot holds.
 861  */
 862 void
 863 dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx)
 864 {
 865         objset_t *mos = dp->dp_meta_objset;
 866 
 867         ASSERT(dp->dp_tmp_userrefs_obj == 0);
 868         ASSERT(dmu_tx_is_syncing(tx));
 869 
 870         dp->dp_tmp_userrefs_obj = zap_create_link(mos, DMU_OT_USERREFS,
 871             DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, tx);
 872 }
 873 
 874 static int
 875 dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj,




 819         dsl_dataset_rele(ds, FTAG);
 820 }
 821 
 822 taskq_t *
 823 dsl_pool_vnrele_taskq(dsl_pool_t *dp)
 824 {
 825         return (dp->dp_vnrele_taskq);
 826 }
 827 
 828 /*
 829  * Walk through the pool-wide zap object of temporary snapshot user holds
 830  * and release them.
 831  */
 832 void
 833 dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp)
 834 {
 835         zap_attribute_t za;
 836         zap_cursor_t zc;
 837         objset_t *mos = dp->dp_meta_objset;
 838         uint64_t zapobj = dp->dp_tmp_userrefs_obj;
 839         nvlist_t *holds;
 840 
 841         if (zapobj == 0)
 842                 return;
 843         ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
 844 
 845         holds = fnvlist_alloc();
 846 
 847         for (zap_cursor_init(&zc, mos, zapobj);
 848             zap_cursor_retrieve(&zc, &za) == 0;
 849             zap_cursor_advance(&zc)) {
 850                 char *htag;
 851                 uint64_t dsobj;
 852                 nvlist_t *tags;
 853 
 854                 htag = strchr(za.za_name, '-');
 855                 *htag = '\0';
 856                 ++htag;
 857                 if (nvlist_lookup_nvlist(holds, za.za_name, &tags) != 0) {
 858                         tags = fnvlist_alloc();
 859                         fnvlist_add_boolean(tags, htag);
 860                         fnvlist_add_nvlist(holds, za.za_name, tags);
 861                         fnvlist_free(tags);
 862                 } else {
 863                         fnvlist_add_boolean(tags, htag);
 864                 }
 865         }
 866         dsl_dataset_user_release_tmp(dp, holds);
 867         fnvlist_free(holds);
 868         zap_cursor_fini(&zc);
 869 }
 870 
 871 /*
 872  * Create the pool-wide zap object for storing temporary snapshot holds.
 873  */
 874 void
 875 dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx)
 876 {
 877         objset_t *mos = dp->dp_meta_objset;
 878 
 879         ASSERT(dp->dp_tmp_userrefs_obj == 0);
 880         ASSERT(dmu_tx_is_syncing(tx));
 881 
 882         dp->dp_tmp_userrefs_obj = zap_create_link(mos, DMU_OT_USERREFS,
 883             DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, tx);
 884 }
 885 
 886 static int
 887 dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj,