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OpenZFS 7004 - dmu_tx_hold_zap() does dnode_hold() 7x on same object

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Using a benchmark which has 32 threads creating 2 million files in the
same directory, on a machine with 16 CPU cores, I observed poor
performance. I noticed that dmu_tx_hold_zap() was using about 30% of
all CPU, and doing dnode_hold() 7 times on the same object (the ZAP
object that is being held).

dmu_tx_hold_zap() keeps a hold on the dnode_t the entire time it is
running, in dmu_tx_hold_t:txh_dnode, so it would be nice to use the
dnode_t that we already have in hand, rather than repeatedly calling
dnode_hold(). To do this, we need to pass the dnode_t down through
all the intermediate calls that dmu_tx_hold_zap() makes, making these
routines take the dnode_t* rather than an objset_t* and a uint64_t
object number. In particular, the following routines will need to have
analogous *_by_dnode() variants created:

dmu_buf_hold_noread()
dmu_buf_hold()
zap_lookup()
zap_lookup_norm()
zap_count_write()
zap_lockdir()
zap_count_write()

This can improve performance on the benchmark described above by 100%,
from 30,000 file creations per second to 60,000. (This improvement is on
top of that provided by working around the object allocation issue. Peak
performance of ~90,000 creations per second was observed with 8 CPUs;
adding CPUs past that decreased performance due to lock contention.) The
CPU used by dmu_tx_hold_zap() was reduced by 88%, from 340 CPU-seconds
to 40 CPU-seconds.

Sponsored by: Intel Corp.

Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/7004
OpenZFS-commit: https://github.com/openzfs/openzfs/pull/109
Closes #4641
Closes #4972
This commit is contained in:
Matthew Ahrens 2016-07-20 15:42:13 -07:00 committed by Brian Behlendorf
parent 8bea981504
commit 2bce8049c3
8 changed files with 146 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/sys/dmu.h
View File

@ -20,7 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2014 by Delphix. All rights reserved.
* Copyright (c) 2011, 2016 by Delphix. All rights reserved.
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2012, Joyent, Inc. All rights reserved.
* Copyright 2014 HybridCluster. All rights reserved.
@ -73,6 +73,7 @@ struct sa_handle;
typedef struct objset objset_t;
typedef struct dmu_tx dmu_tx_t;
typedef struct dsl_dir dsl_dir_t;
typedef struct dnode dnode_t;
typedef enum dmu_object_byteswap {
DMU_BSWAP_UINT8,
@ -420,7 +421,7 @@ dmu_write_embedded(objset_t *os, uint64_t object, uint64_t offset,
#define WP_DMU_SYNC 0x2
#define WP_SPILL 0x4
void dmu_write_policy(objset_t *os, struct dnode *dn, int level, int wp,
void dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp,
struct zio_prop *zp);
/*
* The bonus data is accessed more or less like a regular buffer.
@ -446,7 +447,7 @@ int dmu_rm_spill(objset_t *, uint64_t, dmu_tx_t *);
*/
int dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp);
int dmu_spill_hold_by_dnode(struct dnode *dn, uint32_t flags,
int dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags,
void *tag, dmu_buf_t **dbp);
int dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp);
@ -466,6 +467,8 @@ int dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp);
*/
int dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
void *tag, dmu_buf_t **, int flags);
int dmu_buf_hold_by_dnode(dnode_t *dn, uint64_t offset,
void *tag, dmu_buf_t **dbp, int flags);
/*
* Add a reference to a dmu buffer that has already been held via
@ -620,6 +623,8 @@ void *dmu_buf_remove_user(dmu_buf_t *db, dmu_buf_user_t *user);
void *dmu_buf_get_user(dmu_buf_t *db);
objset_t *dmu_buf_get_objset(dmu_buf_t *db);
dnode_t *dmu_buf_dnode_enter(dmu_buf_t *db);
void dmu_buf_dnode_exit(dmu_buf_t *db);
/* Block until any in-progress dmu buf user evictions complete. */
void dmu_buf_user_evict_wait(void);
@ -799,7 +804,7 @@ extern const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS];
int dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi);
void __dmu_object_info_from_dnode(struct dnode *dn, dmu_object_info_t *doi);
/* Like dmu_object_info, but faster if you have a held dnode in hand. */
void dmu_object_info_from_dnode(struct dnode *dn, dmu_object_info_t *doi);
void dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi);
/* Like dmu_object_info, but faster if you have a held dbuf in hand. */
void dmu_object_info_from_db(dmu_buf_t *db, dmu_object_info_t *doi);
/*

6
include/sys/dnode.h
View File

@ -20,7 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2014 by Delphix. All rights reserved.
* Copyright (c) 2012, 2016 by Delphix. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
*/
@ -187,7 +187,7 @@ typedef struct dnode_phys {
#define DN_SPILL_BLKPTR(dnp) (blkptr_t *)((char *)(dnp) + \
(((dnp)->dn_extra_slots + 1) << DNODE_SHIFT) - (1 << SPA_BLKPTRSHIFT))
typedef struct dnode {
struct dnode {
/*
* Protects the structure of the dnode, including the number of levels
* of indirection (dn_nlevels), dn_maxblkid, and dn_next_*
@ -286,7 +286,7 @@ typedef struct dnode {
/* holds prefetch structure */
struct zfetch dn_zfetch;
} dnode_t;
};
/*
* Adds a level of indirection between the dbuf and the dnode to avoid

9
include/sys/zap.h
View File

@ -236,7 +236,14 @@ int zap_prefetch(objset_t *os, uint64_t zapobj, const char *name);
int zap_prefetch_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
int key_numints);
int zap_count_write(objset_t *os, uint64_t zapobj, const char *name,
int zap_lookup_by_dnode(dnode_t *dn, const char *name,
uint64_t integer_size, uint64_t num_integers, void *buf);
int zap_lookup_norm_by_dnode(dnode_t *dn, const char *name,
uint64_t integer_size, uint64_t num_integers, void *buf,
matchtype_t mt, char *realname, int rn_len,
boolean_t *ncp);
int zap_count_write_by_dnode(dnode_t *dn, const char *name,
int add, uint64_t *towrite, uint64_t *tooverwrite);
/*

17
module/zfs/dbuf.c
View File

@ -21,7 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2012, 2015 by Delphix. All rights reserved.
* Copyright (c) 2012, 2016 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
*/
@ -2843,6 +2843,21 @@ dmu_buf_get_objset(dmu_buf_t *db)
return (dbi->db_objset);
}
dnode_t *
dmu_buf_dnode_enter(dmu_buf_t *db)
{
dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
DB_DNODE_ENTER(dbi);
return (DB_DNODE(dbi));
}
void
dmu_buf_dnode_exit(dmu_buf_t *db)
{
dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
DB_DNODE_EXIT(dbi);
}
static void
dbuf_check_blkptr(dnode_t *dn, dmu_buf_impl_t *db)
{

43
module/zfs/dmu.c
View File

@ -127,6 +127,26 @@ const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
{ zfs_acl_byteswap, "acl" }
};
int
dmu_buf_hold_noread_by_dnode(dnode_t *dn, uint64_t offset,
void *tag, dmu_buf_t **dbp)
{
uint64_t blkid;
dmu_buf_impl_t *db;
blkid = dbuf_whichblock(dn, 0, offset);
rw_enter(&dn->dn_struct_rwlock, RW_READER);
db = dbuf_hold(dn, blkid, tag);
rw_exit(&dn->dn_struct_rwlock);
if (db == NULL) {
*dbp = NULL;
return (SET_ERROR(EIO));
}
*dbp = &db->db;
return (0);
}
int
dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset,
void *tag, dmu_buf_t **dbp)
@ -154,6 +174,29 @@ dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset,
return (err);
}
int
dmu_buf_hold_by_dnode(dnode_t *dn, uint64_t offset,
void *tag, dmu_buf_t **dbp, int flags)
{
int err;
int db_flags = DB_RF_CANFAIL;
if (flags & DMU_READ_NO_PREFETCH)
db_flags |= DB_RF_NOPREFETCH;
err = dmu_buf_hold_noread_by_dnode(dn, offset, tag, dbp);
if (err == 0) {
dmu_buf_impl_t *db = (dmu_buf_impl_t *)(*dbp);
err = dbuf_read(db, NULL, db_flags);
if (err != 0) {
dbuf_rele(db, tag);
*dbp = NULL;
}
}
return (err);
}
int
dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
void *tag, dmu_buf_t **dbp, int flags)

7
module/zfs/dmu_tx.c
View File

@ -21,7 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2012, 2015 by Delphix. All rights reserved.
* Copyright (c) 2012, 2016 by Delphix. All rights reserved.
*/
#include <sys/dmu.h>
@ -794,15 +794,14 @@ dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name)
* access the name in this fat-zap so that we'll check
* for i/o errors to the leaf blocks, etc.
*/
err = zap_lookup(dn->dn_objset, dn->dn_object, name,
8, 0, NULL);
err = zap_lookup_by_dnode(dn, name, 8, 0, NULL);
if (err == EIO) {
tx->tx_err = err;
return;
}
}
err = zap_count_write(dn->dn_objset, dn->dn_object, name, add,
err = zap_count_write_by_dnode(dn, name, add,
&txh->txh_space_towrite, &txh->txh_space_tooverwrite);
/*

19
module/zfs/zap.c
View File

@ -270,6 +270,7 @@ zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
uint64_t blk, off;
int err;
dmu_buf_t *db;
dnode_t *dn;
int bs = FZAP_BLOCK_SHIFT(zap);
ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
@ -277,8 +278,15 @@ zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
blk = idx >> (bs-3);
off = idx & ((1<<(bs-3))-1);
err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
/*
* Note: this is equivalent to dmu_buf_hold(), but we use
* _dnode_enter / _by_dnode because it's faster because we don't
* have to hold the dnode.
*/
dn = dmu_buf_dnode_enter(zap->zap_dbuf);
err = dmu_buf_hold_by_dnode(dn,
(tbl->zt_blk + blk) << bs, FTAG, &db, DMU_READ_NO_PREFETCH);
dmu_buf_dnode_exit(zap->zap_dbuf);
if (err)
return (err);
*valp = ((uint64_t *)db->db_data)[off];
@ -292,9 +300,11 @@ zap_table_load(zap_t *zap, zap_table_phys_t *tbl, uint64_t idx, uint64_t *valp)
*/
blk = (idx*2) >> (bs-3);
err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
dn = dmu_buf_dnode_enter(zap->zap_dbuf);
err = dmu_buf_hold_by_dnode(dn,
(tbl->zt_nextblk + blk) << bs, FTAG, &db,
DMU_READ_NO_PREFETCH);
dmu_buf_dnode_exit(zap->zap_dbuf);
if (err == 0)
dmu_buf_rele(db, FTAG);
}
@ -502,6 +512,7 @@ zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
zap_leaf_t *l;
int bs = FZAP_BLOCK_SHIFT(zap);
int err;
dnode_t *dn;
ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
@ -515,8 +526,10 @@ zap_get_leaf_byblk(zap_t *zap, uint64_t blkid, dmu_tx_t *tx, krw_t lt,
if (blkid == 0)
return (ENOENT);
err = dmu_buf_hold(zap->zap_objset, zap->zap_object,
dn = dmu_buf_dnode_enter(zap->zap_dbuf);
err = dmu_buf_hold_by_dnode(dn,
blkid << bs, NULL, &db, DMU_READ_NO_PREFETCH);
dmu_buf_dnode_exit(zap->zap_dbuf);
if (err)
return (err);

51
module/zfs/zap_micro.c
View File

@ -536,6 +536,24 @@ zap_lockdir_impl(dmu_buf_t *db, void *tag, dmu_tx_t *tx,
return (0);
}
static int
zap_lockdir_by_dnode(dnode_t *dn, dmu_tx_t *tx,
krw_t lti, boolean_t fatreader, boolean_t adding, void *tag, zap_t **zapp)
{
dmu_buf_t *db;
int err;
err = dmu_buf_hold_by_dnode(dn, 0, tag, &db, DMU_READ_NO_PREFETCH);
if (err != 0) {
return (err);
}
err = zap_lockdir_impl(db, tag, tx, lti, fatreader, adding, zapp);
if (err != 0) {
dmu_buf_rele(db, tag);
}
return (err);
}
int
zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
krw_t lti, boolean_t fatreader, boolean_t adding, void *tag, zap_t **zapp)
@ -927,6 +945,33 @@ zap_prefetch(objset_t *os, uint64_t zapobj, const char *name)
return (err);
}
int
zap_lookup_by_dnode(dnode_t *dn, const char *name,
uint64_t integer_size, uint64_t num_integers, void *buf)
{
return (zap_lookup_norm_by_dnode(dn, name, integer_size,
num_integers, buf, MT_EXACT, NULL, 0, NULL));
}
int
zap_lookup_norm_by_dnode(dnode_t *dn, const char *name,
uint64_t integer_size, uint64_t num_integers, void *buf,
matchtype_t mt, char *realname, int rn_len,
boolean_t *ncp)
{
zap_t *zap;
int err;
err = zap_lockdir_by_dnode(dn, NULL, RW_READER, TRUE, FALSE,
FTAG, &zap);
if (err != 0)
return (err);
err = zap_lookup_impl(zap, name, integer_size,
num_integers, buf, mt, realname, rn_len, ncp);
zap_unlockdir(zap, FTAG);
return (err);
}
int
zap_prefetch_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
int key_numints)
@ -1460,7 +1505,7 @@ zap_get_stats(objset_t *os, uint64_t zapobj, zap_stats_t *zs)
}
int
zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
zap_count_write_by_dnode(dnode_t *dn, const char *name, int add,
uint64_t *towrite, uint64_t *tooverwrite)
{
zap_t *zap;
@ -1488,7 +1533,7 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
* At present we are just evaluating the possibility of this operation
* and hence we do not want to trigger an upgrade.
*/
err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE,
err = zap_lockdir_by_dnode(dn, NULL, RW_READER, TRUE, FALSE,
FTAG, &zap);
if (err != 0)
return (err);
@ -1552,7 +1597,7 @@ EXPORT_SYMBOL(zap_lookup_uint64);
EXPORT_SYMBOL(zap_contains);
EXPORT_SYMBOL(zap_prefetch);
EXPORT_SYMBOL(zap_prefetch_uint64);
EXPORT_SYMBOL(zap_count_write);
EXPORT_SYMBOL(zap_count_write_by_dnode);
EXPORT_SYMBOL(zap_add);
EXPORT_SYMBOL(zap_add_uint64);
EXPORT_SYMBOL(zap_update);