kernel_optimize_test/fs/btrfs/btrfs_inode.h
Filipe Manana 487781796d btrfs: make fast fsyncs wait only for writeback
Currently regardless of a full or a fast fsync we always wait for ordered
extents to complete, and then start logging the inode after that. However
for fast fsyncs we can just wait for the writeback to complete, we don't
need to wait for the ordered extents to complete since we use the list of
modified extents maps to figure out which extents we must log and we can
get their checksums directly from the ordered extents that are still in
flight, otherwise look them up from the checksums tree.

Until commit b5e6c3e170 ("btrfs: always wait on ordered extents at
fsync time"), for fast fsyncs, we used to start logging without even
waiting for the writeback to complete first, we would wait for it to
complete after logging, while holding a transaction open, which lead to
performance issues when using cgroups and probably for other cases too,
as wait for IO while holding a transaction handle should be avoided as
much as possible. After that, for fast fsyncs, we started to wait for
ordered extents to complete before starting to log, which adds some
latency to fsyncs and we even got at least one report about a performance
drop which bisected to that particular change:

https://lore.kernel.org/linux-btrfs/20181109215148.GF23260@techsingularity.net/

This change makes fast fsyncs only wait for writeback to finish before
starting to log the inode, instead of waiting for both the writeback to
finish and for the ordered extents to complete. This brings back part of
the logic we had that extracts checksums from in flight ordered extents,
which are not yet in the checksums tree, and making sure transaction
commits wait for the completion of ordered extents previously logged
(by far most of the time they have already completed by the time a
transaction commit starts, resulting in no wait at all), to avoid any
data loss if an ordered extent completes after the transaction used to
log an inode is committed, followed by a power failure.

When there are no other tasks accessing the checksums and the subvolume
btrees, the ordered extent completion is pretty fast, typically taking
100 to 200 microseconds only in my observations. However when there are
other tasks accessing these btrees, ordered extent completion can take a
lot more time due to lock contention on nodes and leaves of these btrees.
I've seen cases over 2 milliseconds, which starts to be significant. In
particular when we do have concurrent fsyncs against different files there
is a lot of contention on the checksums btree, since we have many tasks
writing the checksums into the btree and other tasks that already started
the logging phase are doing lookups for checksums in the btree.

This change also turns all ranged fsyncs into full ranged fsyncs, which
is something we already did when not using the NO_HOLES features or when
doing a full fsync. This is to guarantee we never miss checksums due to
writeback having been triggered only for a part of an extent, and we end
up logging the full extent but only checksums for the written range, which
results in missing checksums after log replay. Allowing ranged fsyncs to
operate again only in the original range, when using the NO_HOLES feature
and doing a fast fsync is doable but requires some non trivial changes to
the writeback path, which can always be worked on later if needed, but I
don't think they are a very common use case.

Several tests were performed using fio for different numbers of concurrent
jobs, each writing and fsyncing its own file, for both sequential and
random file writes. The tests were run on bare metal, no virtualization,
on a box with 12 cores (Intel i7-8700), 64Gb of RAM and a NVMe device,
with a kernel configuration that is the default of typical distributions
(debian in this case), without debug options enabled (kasan, kmemleak,
slub debug, debug of page allocations, lock debugging, etc).

The following script that calls fio was used:

  $ cat test-fsync.sh
  #!/bin/bash

  DEV=/dev/nvme0n1
  MNT=/mnt/btrfs
  MOUNT_OPTIONS="-o ssd -o space_cache=v2"
  MKFS_OPTIONS="-d single -m single"

  if [ $# -ne 5 ]; then
    echo "Use $0 NUM_JOBS FILE_SIZE FSYNC_FREQ BLOCK_SIZE [write|randwrite]"
    exit 1
  fi

  NUM_JOBS=$1
  FILE_SIZE=$2
  FSYNC_FREQ=$3
  BLOCK_SIZE=$4
  WRITE_MODE=$5

  if [ "$WRITE_MODE" != "write" ] && [ "$WRITE_MODE" != "randwrite" ]; then
    echo "Invalid WRITE_MODE, must be 'write' or 'randwrite'"
    exit 1
  fi

  cat <<EOF > /tmp/fio-job.ini
  [writers]
  rw=$WRITE_MODE
  fsync=$FSYNC_FREQ
  fallocate=none
  group_reporting=1
  direct=0
  bs=$BLOCK_SIZE
  ioengine=sync
  size=$FILE_SIZE
  directory=$MNT
  numjobs=$NUM_JOBS
  EOF

  echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

  echo
  echo "Using config:"
  echo
  cat /tmp/fio-job.ini
  echo

  umount $MNT &> /dev/null
  mkfs.btrfs -f $MKFS_OPTIONS $DEV
  mount $MOUNT_OPTIONS $DEV $MNT
  fio /tmp/fio-job.ini
  umount $MNT

The results were the following:

*************************
*** sequential writes ***
*************************

==== 1 job, 8GiB file, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=36.6MiB/s (38.4MB/s), 36.6MiB/s-36.6MiB/s (38.4MB/s-38.4MB/s), io=8192MiB (8590MB), run=223689-223689msec

After patch:

WRITE: bw=40.2MiB/s (42.1MB/s), 40.2MiB/s-40.2MiB/s (42.1MB/s-42.1MB/s), io=8192MiB (8590MB), run=203980-203980msec
(+9.8%, -8.8% runtime)

==== 2 jobs, 4GiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=35.8MiB/s (37.5MB/s), 35.8MiB/s-35.8MiB/s (37.5MB/s-37.5MB/s), io=8192MiB (8590MB), run=228950-228950msec

After patch:

WRITE: bw=43.5MiB/s (45.6MB/s), 43.5MiB/s-43.5MiB/s (45.6MB/s-45.6MB/s), io=8192MiB (8590MB), run=188272-188272msec
(+21.5% throughput, -17.8% runtime)

==== 4 jobs, 2GiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=50.1MiB/s (52.6MB/s), 50.1MiB/s-50.1MiB/s (52.6MB/s-52.6MB/s), io=8192MiB (8590MB), run=163446-163446msec

After patch:

WRITE: bw=64.5MiB/s (67.6MB/s), 64.5MiB/s-64.5MiB/s (67.6MB/s-67.6MB/s), io=8192MiB (8590MB), run=126987-126987msec
(+28.7% throughput, -22.3% runtime)

==== 8 jobs, 1GiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=64.0MiB/s (68.1MB/s), 64.0MiB/s-64.0MiB/s (68.1MB/s-68.1MB/s), io=8192MiB (8590MB), run=126075-126075msec

After patch:

WRITE: bw=86.8MiB/s (91.0MB/s), 86.8MiB/s-86.8MiB/s (91.0MB/s-91.0MB/s), io=8192MiB (8590MB), run=94358-94358msec
(+35.6% throughput, -25.2% runtime)

==== 16 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=79.8MiB/s (83.6MB/s), 79.8MiB/s-79.8MiB/s (83.6MB/s-83.6MB/s), io=8192MiB (8590MB), run=102694-102694msec

After patch:

WRITE: bw=107MiB/s (112MB/s), 107MiB/s-107MiB/s (112MB/s-112MB/s), io=8192MiB (8590MB), run=76446-76446msec
(+34.1% throughput, -25.6% runtime)

==== 32 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=93.2MiB/s (97.7MB/s), 93.2MiB/s-93.2MiB/s (97.7MB/s-97.7MB/s), io=16.0GiB (17.2GB), run=175836-175836msec

After patch:

WRITE: bw=111MiB/s (117MB/s), 111MiB/s-111MiB/s (117MB/s-117MB/s), io=16.0GiB (17.2GB), run=147001-147001msec
(+19.1% throughput, -16.4% runtime)

==== 64 jobs, 512MiB files, fsync frequency 1, block size 64KiB ====

Before patch:

WRITE: bw=108MiB/s (114MB/s), 108MiB/s-108MiB/s (114MB/s-114MB/s), io=32.0GiB (34.4GB), run=302656-302656msec

After patch:

WRITE: bw=133MiB/s (140MB/s), 133MiB/s-133MiB/s (140MB/s-140MB/s), io=32.0GiB (34.4GB), run=246003-246003msec
(+23.1% throughput, -18.7% runtime)

************************
***   random writes  ***
************************

==== 1 job, 8GiB file, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=11.5MiB/s (12.0MB/s), 11.5MiB/s-11.5MiB/s (12.0MB/s-12.0MB/s), io=8192MiB (8590MB), run=714281-714281msec

After patch:

WRITE: bw=11.6MiB/s (12.2MB/s), 11.6MiB/s-11.6MiB/s (12.2MB/s-12.2MB/s), io=8192MiB (8590MB), run=705959-705959msec
(+0.9% throughput, -1.7% runtime)

==== 2 jobs, 4GiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=12.8MiB/s (13.5MB/s), 12.8MiB/s-12.8MiB/s (13.5MB/s-13.5MB/s), io=8192MiB (8590MB), run=638101-638101msec

After patch:

WRITE: bw=13.1MiB/s (13.7MB/s), 13.1MiB/s-13.1MiB/s (13.7MB/s-13.7MB/s), io=8192MiB (8590MB), run=625374-625374msec
(+2.3% throughput, -2.0% runtime)

==== 4 jobs, 2GiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=15.4MiB/s (16.2MB/s), 15.4MiB/s-15.4MiB/s (16.2MB/s-16.2MB/s), io=8192MiB (8590MB), run=531146-531146msec

After patch:

WRITE: bw=17.8MiB/s (18.7MB/s), 17.8MiB/s-17.8MiB/s (18.7MB/s-18.7MB/s), io=8192MiB (8590MB), run=460431-460431msec
(+15.6% throughput, -13.3% runtime)

==== 8 jobs, 1GiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=19.9MiB/s (20.8MB/s), 19.9MiB/s-19.9MiB/s (20.8MB/s-20.8MB/s), io=8192MiB (8590MB), run=412664-412664msec

After patch:

WRITE: bw=22.2MiB/s (23.3MB/s), 22.2MiB/s-22.2MiB/s (23.3MB/s-23.3MB/s), io=8192MiB (8590MB), run=368589-368589msec
(+11.6% throughput, -10.7% runtime)

==== 16 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=29.3MiB/s (30.7MB/s), 29.3MiB/s-29.3MiB/s (30.7MB/s-30.7MB/s), io=8192MiB (8590MB), run=279924-279924msec

After patch:

WRITE: bw=30.4MiB/s (31.9MB/s), 30.4MiB/s-30.4MiB/s (31.9MB/s-31.9MB/s), io=8192MiB (8590MB), run=269258-269258msec
(+3.8% throughput, -3.8% runtime)

==== 32 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=36.9MiB/s (38.7MB/s), 36.9MiB/s-36.9MiB/s (38.7MB/s-38.7MB/s), io=16.0GiB (17.2GB), run=443581-443581msec

After patch:

WRITE: bw=41.6MiB/s (43.6MB/s), 41.6MiB/s-41.6MiB/s (43.6MB/s-43.6MB/s), io=16.0GiB (17.2GB), run=394114-394114msec
(+12.7% throughput, -11.2% runtime)

==== 64 jobs, 512MiB files, fsync frequency 16, block size 4KiB ====

Before patch:

WRITE: bw=45.9MiB/s (48.1MB/s), 45.9MiB/s-45.9MiB/s (48.1MB/s-48.1MB/s), io=32.0GiB (34.4GB), run=714614-714614msec

After patch:

WRITE: bw=48.8MiB/s (51.1MB/s), 48.8MiB/s-48.8MiB/s (51.1MB/s-51.1MB/s), io=32.0GiB (34.4GB), run=672087-672087msec
(+6.3% throughput, -6.0% runtime)

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-10-07 12:06:56 +02:00

380 lines
10 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2007 Oracle. All rights reserved.
*/
#ifndef BTRFS_INODE_H
#define BTRFS_INODE_H
#include <linux/hash.h>
#include <linux/refcount.h>
#include "extent_map.h"
#include "extent_io.h"
#include "ordered-data.h"
#include "delayed-inode.h"
/*
* ordered_data_close is set by truncate when a file that used
* to have good data has been truncated to zero. When it is set
* the btrfs file release call will add this inode to the
* ordered operations list so that we make sure to flush out any
* new data the application may have written before commit.
*/
enum {
BTRFS_INODE_ORDERED_DATA_CLOSE,
BTRFS_INODE_DUMMY,
BTRFS_INODE_IN_DEFRAG,
BTRFS_INODE_HAS_ASYNC_EXTENT,
/*
* Always set under the VFS' inode lock, otherwise it can cause races
* during fsync (we start as a fast fsync and then end up in a full
* fsync racing with ordered extent completion).
*/
BTRFS_INODE_NEEDS_FULL_SYNC,
BTRFS_INODE_COPY_EVERYTHING,
BTRFS_INODE_IN_DELALLOC_LIST,
BTRFS_INODE_READDIO_NEED_LOCK,
BTRFS_INODE_HAS_PROPS,
BTRFS_INODE_SNAPSHOT_FLUSH,
};
/* in memory btrfs inode */
struct btrfs_inode {
/* which subvolume this inode belongs to */
struct btrfs_root *root;
/* key used to find this inode on disk. This is used by the code
* to read in roots of subvolumes
*/
struct btrfs_key location;
/*
* Lock for counters and all fields used to determine if the inode is in
* the log or not (last_trans, last_sub_trans, last_log_commit,
* logged_trans).
*/
spinlock_t lock;
/* the extent_tree has caches of all the extent mappings to disk */
struct extent_map_tree extent_tree;
/* the io_tree does range state (DIRTY, LOCKED etc) */
struct extent_io_tree io_tree;
/* special utility tree used to record which mirrors have already been
* tried when checksums fail for a given block
*/
struct extent_io_tree io_failure_tree;
/*
* Keep track of where the inode has extent items mapped in order to
* make sure the i_size adjustments are accurate
*/
struct extent_io_tree file_extent_tree;
/* held while logging the inode in tree-log.c */
struct mutex log_mutex;
/* used to order data wrt metadata */
struct btrfs_ordered_inode_tree ordered_tree;
/* list of all the delalloc inodes in the FS. There are times we need
* to write all the delalloc pages to disk, and this list is used
* to walk them all.
*/
struct list_head delalloc_inodes;
/* node for the red-black tree that links inodes in subvolume root */
struct rb_node rb_node;
unsigned long runtime_flags;
/* Keep track of who's O_SYNC/fsyncing currently */
atomic_t sync_writers;
/* full 64 bit generation number, struct vfs_inode doesn't have a big
* enough field for this.
*/
u64 generation;
/*
* transid of the trans_handle that last modified this inode
*/
u64 last_trans;
/*
* transid that last logged this inode
*/
u64 logged_trans;
/*
* log transid when this inode was last modified
*/
int last_sub_trans;
/* a local copy of root's last_log_commit */
int last_log_commit;
/* total number of bytes pending delalloc, used by stat to calc the
* real block usage of the file
*/
u64 delalloc_bytes;
/*
* Total number of bytes pending delalloc that fall within a file
* range that is either a hole or beyond EOF (and no prealloc extent
* exists in the range). This is always <= delalloc_bytes.
*/
u64 new_delalloc_bytes;
/*
* total number of bytes pending defrag, used by stat to check whether
* it needs COW.
*/
u64 defrag_bytes;
/*
* the size of the file stored in the metadata on disk. data=ordered
* means the in-memory i_size might be larger than the size on disk
* because not all the blocks are written yet.
*/
u64 disk_i_size;
/*
* if this is a directory then index_cnt is the counter for the index
* number for new files that are created
*/
u64 index_cnt;
/* Cache the directory index number to speed the dir/file remove */
u64 dir_index;
/* the fsync log has some corner cases that mean we have to check
* directories to see if any unlinks have been done before
* the directory was logged. See tree-log.c for all the
* details
*/
u64 last_unlink_trans;
/*
* The id/generation of the last transaction where this inode was
* either the source or the destination of a clone/dedupe operation.
* Used when logging an inode to know if there are shared extents that
* need special care when logging checksum items, to avoid duplicate
* checksum items in a log (which can lead to a corruption where we end
* up with missing checksum ranges after log replay).
* Protected by the vfs inode lock.
*/
u64 last_reflink_trans;
/*
* Number of bytes outstanding that are going to need csums. This is
* used in ENOSPC accounting.
*/
u64 csum_bytes;
/* flags field from the on disk inode */
u32 flags;
/*
* Counters to keep track of the number of extent item's we may use due
* to delalloc and such. outstanding_extents is the number of extent
* items we think we'll end up using, and reserved_extents is the number
* of extent items we've reserved metadata for.
*/
unsigned outstanding_extents;
struct btrfs_block_rsv block_rsv;
/*
* Cached values of inode properties
*/
unsigned prop_compress; /* per-file compression algorithm */
/*
* Force compression on the file using the defrag ioctl, could be
* different from prop_compress and takes precedence if set
*/
unsigned defrag_compress;
struct btrfs_delayed_node *delayed_node;
/* File creation time. */
struct timespec64 i_otime;
/* Hook into fs_info->delayed_iputs */
struct list_head delayed_iput;
/*
* To avoid races between lockless (i_mutex not held) direct IO writes
* and concurrent fsync requests. Direct IO writes must acquire read
* access on this semaphore for creating an extent map and its
* corresponding ordered extent. The fast fsync path must acquire write
* access on this semaphore before it collects ordered extents and
* extent maps.
*/
struct rw_semaphore dio_sem;
struct inode vfs_inode;
};
static inline struct btrfs_inode *BTRFS_I(const struct inode *inode)
{
return container_of(inode, struct btrfs_inode, vfs_inode);
}
static inline unsigned long btrfs_inode_hash(u64 objectid,
const struct btrfs_root *root)
{
u64 h = objectid ^ (root->root_key.objectid * GOLDEN_RATIO_PRIME);
#if BITS_PER_LONG == 32
h = (h >> 32) ^ (h & 0xffffffff);
#endif
return (unsigned long)h;
}
static inline void btrfs_insert_inode_hash(struct inode *inode)
{
unsigned long h = btrfs_inode_hash(inode->i_ino, BTRFS_I(inode)->root);
__insert_inode_hash(inode, h);
}
static inline u64 btrfs_ino(const struct btrfs_inode *inode)
{
u64 ino = inode->location.objectid;
/*
* !ino: btree_inode
* type == BTRFS_ROOT_ITEM_KEY: subvol dir
*/
if (!ino || inode->location.type == BTRFS_ROOT_ITEM_KEY)
ino = inode->vfs_inode.i_ino;
return ino;
}
static inline void btrfs_i_size_write(struct btrfs_inode *inode, u64 size)
{
i_size_write(&inode->vfs_inode, size);
inode->disk_i_size = size;
}
static inline bool btrfs_is_free_space_inode(struct btrfs_inode *inode)
{
struct btrfs_root *root = inode->root;
if (root == root->fs_info->tree_root &&
btrfs_ino(inode) != BTRFS_BTREE_INODE_OBJECTID)
return true;
if (inode->location.objectid == BTRFS_FREE_INO_OBJECTID)
return true;
return false;
}
static inline bool is_data_inode(struct inode *inode)
{
return btrfs_ino(BTRFS_I(inode)) != BTRFS_BTREE_INODE_OBJECTID;
}
static inline void btrfs_mod_outstanding_extents(struct btrfs_inode *inode,
int mod)
{
lockdep_assert_held(&inode->lock);
inode->outstanding_extents += mod;
if (btrfs_is_free_space_inode(inode))
return;
trace_btrfs_inode_mod_outstanding_extents(inode->root, btrfs_ino(inode),
mod);
}
static inline int btrfs_inode_in_log(struct btrfs_inode *inode, u64 generation)
{
int ret = 0;
spin_lock(&inode->lock);
if (inode->logged_trans == generation &&
inode->last_sub_trans <= inode->last_log_commit &&
inode->last_sub_trans <= inode->root->last_log_commit) {
/*
* After a ranged fsync we might have left some extent maps
* (that fall outside the fsync's range). So return false
* here if the list isn't empty, to make sure btrfs_log_inode()
* will be called and process those extent maps.
*/
smp_mb();
if (list_empty(&inode->extent_tree.modified_extents))
ret = 1;
}
spin_unlock(&inode->lock);
return ret;
}
struct btrfs_dio_private {
struct inode *inode;
u64 logical_offset;
u64 disk_bytenr;
u64 bytes;
/*
* References to this structure. There is one reference per in-flight
* bio plus one while we're still setting up.
*/
refcount_t refs;
/* dio_bio came from fs/direct-io.c */
struct bio *dio_bio;
/* Array of checksums */
u8 csums[];
};
/*
* Disable DIO read nolock optimization, so new dio readers will be forced
* to grab i_mutex. It is used to avoid the endless truncate due to
* nonlocked dio read.
*/
static inline void btrfs_inode_block_unlocked_dio(struct btrfs_inode *inode)
{
set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
smp_mb();
}
static inline void btrfs_inode_resume_unlocked_dio(struct btrfs_inode *inode)
{
smp_mb__before_atomic();
clear_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
}
/* Array of bytes with variable length, hexadecimal format 0x1234 */
#define CSUM_FMT "0x%*phN"
#define CSUM_FMT_VALUE(size, bytes) size, bytes
static inline void btrfs_print_data_csum_error(struct btrfs_inode *inode,
u64 logical_start, u8 *csum, u8 *csum_expected, int mirror_num)
{
struct btrfs_root *root = inode->root;
struct btrfs_super_block *sb = root->fs_info->super_copy;
const u16 csum_size = btrfs_super_csum_size(sb);
/* Output minus objectid, which is more meaningful */
if (root->root_key.objectid >= BTRFS_LAST_FREE_OBJECTID)
btrfs_warn_rl(root->fs_info,
"csum failed root %lld ino %lld off %llu csum " CSUM_FMT " expected csum " CSUM_FMT " mirror %d",
root->root_key.objectid, btrfs_ino(inode),
logical_start,
CSUM_FMT_VALUE(csum_size, csum),
CSUM_FMT_VALUE(csum_size, csum_expected),
mirror_num);
else
btrfs_warn_rl(root->fs_info,
"csum failed root %llu ino %llu off %llu csum " CSUM_FMT " expected csum " CSUM_FMT " mirror %d",
root->root_key.objectid, btrfs_ino(inode),
logical_start,
CSUM_FMT_VALUE(csum_size, csum),
CSUM_FMT_VALUE(csum_size, csum_expected),
mirror_num);
}
#endif