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Btrfs: Allocator Hints: updates to read_stats

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Forza 2025-04-21 06:30:04 +02:00
parent 769ae8ee5c
commit bd9da52cc4
1 changed files with 329 additions and 27 deletions
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Btrfs/Allocator Hints/btrfs_allocator_hints-6.12_v4.patch
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@ -1,7 +1,7 @@
From 5e49c78f38cc7f5b7ec012021c8422c1db98ef7e Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:04 +0200
Subject: [PATCH 01/27] btrfs: add flags to give an hint to the chunk allocator
Subject: [PATCH 01/31] btrfs: add flags to give an hint to the chunk allocator
Add the following flags to give an hint about which chunk should be
allocated in which a disk.
@ -50,7 +50,7 @@ index fc29d273845d84..71c6135dc7cfb2 100644
From 160344ae9ae37b32593adc43716172c37b0a734c Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:05 +0200
Subject: [PATCH 02/27] btrfs: export dev_item.type in
Subject: [PATCH 02/31] btrfs: export dev_item.type in
/sys/fs/btrfs/<uuid>/devinfo/<devid>/type
Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
@ -91,7 +91,7 @@ index 03926ad467c919..fe07a7cbcf74c4 100644
From 29637f2e3a69fe77a8097bd772a8a7803b9ec576 Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:06 +0200
Subject: [PATCH 03/27] btrfs: change the DEV_ITEM 'type' field via sysfs
Subject: [PATCH 03/31] btrfs: change the DEV_ITEM 'type' field via sysfs
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
@ -197,7 +197,7 @@ index 4481575dd70f35..7bb14d51bffc58 100644
From 970b99e160487e9765b6e7db9f8a89a96ce79811 Mon Sep 17 00:00:00 2001
From: Goffredo Baroncelli <kreijack@inwind.it>
Date: Sun, 24 Oct 2021 17:31:07 +0200
Subject: [PATCH 04/27] btrfs: add allocator_hint mode
Subject: [PATCH 04/31] btrfs: add allocator_hint mode
When this mode is enabled, the chunk allocation policy is modified as
follow.
@ -388,7 +388,7 @@ index 7bb14d51bffc58..f3c5437e270a22 100644
From 1c1f2e27d3055b7721468c6980479a043f48e2b3 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kk@netactive.de>
Date: Thu, 27 Jun 2024 20:05:58 +0200
Subject: [PATCH 05/27] btrfs: add allocator_hint for no allocation preferred
Subject: [PATCH 05/31] btrfs: add allocator_hint for no allocation preferred
This is useful where you want to prevent new allocations of chunks on a
disk which is going to removed from the pool anyways, e.g. due to bad
@ -441,7 +441,7 @@ index 71c6135dc7cfb2..92bcc59b129a97 100644
From 82553effe6b655f97478b6d13df7ab0ecc192e58 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Fri, 6 Dec 2024 00:55:31 +0100
Subject: [PATCH 06/27] btrfs: add allocator_hint to disable allocation
Subject: [PATCH 06/31] btrfs: add allocator_hint to disable allocation
completely
This is useful where you want to prevent new allocations of chunks to
@ -516,7 +516,7 @@ index 92bcc59b129a97..3db20734aacfc6 100644
From 10248db4c682397c83b99daa2de4ee0e587c0be2 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:31 +0800
Subject: [PATCH 07/27] btrfs: simplify output formatting in
Subject: [PATCH 07/31] btrfs: simplify output formatting in
btrfs_read_policy_show
Refactor the logic in btrfs_read_policy_show() to streamline the
@ -562,7 +562,7 @@ index 3675d961b39a2a..cde47f1c11757f 100644
From 4a49a279c14d9003fd7d4865706bc78142bf1645 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:30 +0800
Subject: [PATCH 08/27] btrfs: initialize fs_devices->fs_info earlier
Subject: [PATCH 08/31] btrfs: initialize fs_devices->fs_info earlier
Currently, fs_devices->fs_info is initialized in btrfs_init_devices_late(),
but this occurs too late for find_live_mirror(), which is invoked by
@ -606,7 +606,7 @@ index 99d2c60ac2bf3e..21cc02df8edf06 100644
From ccb29226710d52abbd737fd0b2f438022c045af4 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:32 +0800
Subject: [PATCH 09/27] btrfs: add btrfs_read_policy_to_enum helper and
Subject: [PATCH 09/31] btrfs: add btrfs_read_policy_to_enum helper and
refactor read policy store
Introduce the `btrfs_read_policy_to_enum` helper function to simplify the
@ -683,7 +683,7 @@ index cde47f1c11757f..8540af0807648e 100644
From cf73e9084375ab73182d3a2d510e878a137a9664 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:34 +0800
Subject: [PATCH 10/27] btrfs: add tracking of read blocks for read policy
Subject: [PATCH 10/31] btrfs: add tracking of read blocks for read policy
Add fs_devices::read_cnt_blocks to track read blocks, initialize it in
open_fs_devices() and clean it up in close_fs_devices().
@ -801,7 +801,7 @@ index f3c5437e270a22..91a2358b74c91f 100644
From 7070070e90e889d165590aa05f02e671d041d12c Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Mon, 16 Sep 2024 18:18:25 +0930
Subject: [PATCH 11/27] btrfs: introduce CONFIG_BTRFS_EXPERIMENTAL from 6.13
Subject: [PATCH 11/31] btrfs: introduce CONFIG_BTRFS_EXPERIMENTAL from 6.13
CONFIG_BTRFS_EXPERIMENTAL is needed by the RAID1 balancing patches but
we don't want to use the full scope of the 6.13 patch because it also
@ -838,7 +838,7 @@ index 4fb925e8c981d8..ead317f1eeb859 100644
From 3efa6c755e4ae0dc36f606b329b10587f24dcab3 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:33 +0800
Subject: [PATCH 12/27] btrfs: handle value associated with read policy
Subject: [PATCH 12/31] btrfs: handle value associated with read policy
parameter
This change enables specifying additional configuration values alongside
@ -901,7 +901,7 @@ index 8540af0807648e..b0e624c0598f48 100644
From 687cdc03a694afb2236c7c87de458c519be771ea Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:35 +0800
Subject: [PATCH 13/27] btrfs: introduce round-robin read policy
Subject: [PATCH 13/31] btrfs: introduce round-robin read policy
This feature balances I/O across the striped devices when reading from
mirrored blocks.
@ -1130,7 +1130,7 @@ index 91a2358b74c91f..65d56bffc6ef8b 100644
From 328002ad27e90dc8ff6b7c2022711b6f0df74a01 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:36 +0800
Subject: [PATCH 14/27] btrfs: add RAID1 preferred read device
Subject: [PATCH 14/31] btrfs: add RAID1 preferred read device
When there's stale data on a mirrored device, this feature lets you choose
which device to read from. Mainly used for testing.
@ -1276,7 +1276,7 @@ index 65d56bffc6ef8b..d8075ad17a6d3a 100644
From 5084cf69a0e706dfcae5e594d915e46a124fb25c Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:37 +0800
Subject: [PATCH 15/27] btrfs: expose experimental mode in module information
Subject: [PATCH 15/31] btrfs: expose experimental mode in module information
Commit c9c49e8f157e ("btrfs: split out CONFIG_BTRFS_EXPERIMENTAL from
CONFIG_BTRFS_DEBUG") introduces a way to enable or disable experimental
@ -1307,7 +1307,7 @@ index c64d0713412231..4742bb2af601a7 100644
From fd9d23cf84c07baec0ba5d4bbd9ecd4c0e671e47 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:38 +0800
Subject: [PATCH 16/27] btrfs: enable read policy configuration via modprobe
Subject: [PATCH 16/31] btrfs: enable read policy configuration via modprobe
parameter
This update allows configuring the `read_policy` methods using a
@ -1454,7 +1454,7 @@ index a2a0af8f6a9f94..f61844fc2da9ab 100644
From 77f79e1f0d91253b9a2aa0ff975bf34ecf3d243e Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 2 Jan 2025 02:06:39 +0800
Subject: [PATCH 17/27] btrfs: modload to print read policy status
Subject: [PATCH 17/31] btrfs: modload to print read policy status
Modified the Btrfs loading message to include the read policy status
if the experimental feature is enabled.
@ -1490,7 +1490,7 @@ index 448db8974cda70..ea5ff01881d706 100644
From ea9e632401927e9c38ae4b3e505fff377535f58b Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Fri, 11 Oct 2024 10:49:17 +0800
Subject: [PATCH 18/27] btrfs: use the path with the lowest latency for RAID1
Subject: [PATCH 18/31] btrfs: use the path with the lowest latency for RAID1
reads
This feature aims to direct the read I/O to the device with the lowest
@ -1605,7 +1605,7 @@ index d8075ad17a6d3a..6c1f219f83b388 100644
From 680350c9732c58e321968974868836bf13ec5c96 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Wed, 9 Apr 2025 14:07:18 +0200
Subject: [PATCH 19/27] btrfs: move latency-based selection into helper
Subject: [PATCH 19/31] btrfs: move latency-based selection into helper
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
@ -1688,7 +1688,7 @@ index a36c2bfa339785..c2f235a02a79ea 100644
From 1f255624630f889fbd9e268b8d7a77f5ed68fa8c Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Wed, 9 Apr 2025 15:21:14 +0200
Subject: [PATCH 20/27] btrfs: fix btrfs_read_rr to use the actual number of
Subject: [PATCH 20/31] btrfs: fix btrfs_read_rr to use the actual number of
stripes
While num_stripes is identical to index at the end of the loop, index
@ -1722,7 +1722,7 @@ index c2f235a02a79ea..63384cd731ded2 100644
From c26c5bdfbeea36dd89fcbefe1c86561a5113869a Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Tue, 15 Apr 2025 09:04:57 +0200
Subject: [PATCH 21/27] btrfs: create a helper instead of open coding device
Subject: [PATCH 21/31] btrfs: create a helper instead of open coding device
latency calculation
Signed-off-by: Kai Krakow <kai@kaishome.de>
@ -1797,7 +1797,7 @@ index 63384cd731ded2..14baa1b391a936 100644
From e54bf3f05a0c202c8637206b9a4bb03b1e5fe42f Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Tue, 15 Apr 2025 01:28:06 +0200
Subject: [PATCH 22/27] btrfs: add filtering by latency to btrfs_read_rr
Subject: [PATCH 22/31] btrfs: add filtering by latency to btrfs_read_rr
This introduces a new parameter to btrfs_read_rr to select whether we
filter for latency. In case the caller passes latency, we return -1 if
@ -1861,7 +1861,7 @@ index 14baa1b391a936..ff6fd21aaa3226 100644
From b606dcc6ff4a175a3e80a17bb9a85f85a0c9ec03 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Fri, 18 Apr 2025 23:31:04 +0200
Subject: [PATCH 23/27] btrfs: add hybrid latency-rr read policy
Subject: [PATCH 23/31] btrfs: add hybrid latency-rr read policy
This mode combines latency and round-robin modes by considering all
stripes within 125% of the minimum latency. It falls back to round-robin
@ -1994,7 +1994,7 @@ index 6c1f219f83b388..a6e8a722d9c742 100644
From 5f850824c0b496809d10b8c217c1f347f2f6377e Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Wed, 16 Apr 2025 22:06:37 +0200
Subject: [PATCH 24/27] btrfs: add devinfo read stats to sysfs
Subject: [PATCH 24/31] btrfs: add devinfo read stats to sysfs
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
@ -2053,7 +2053,7 @@ index 2014475af9716e..d629ececa0b65e 100644
From 127de63e502294bc6c27a9ae54208481a9b0cb51 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Wed, 16 Apr 2025 22:52:14 +0200
Subject: [PATCH 25/27] btrfs: add last IO age to sysfs read_stats
Subject: [PATCH 25/31] btrfs: add last IO age to sysfs read_stats
Each time a stripe is going to be selected, increase a counter in each
possible stripe. After selecting a stripe, reset the counter to zero.
@ -2147,7 +2147,7 @@ index a6e8a722d9c742..f2807a7463bf17 100644
From 911a9ed3b04a378537f16669676cfea6a557ec57 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Thu, 17 Apr 2025 00:26:03 +0200
Subject: [PATCH 26/27] btrfs: probe read latency if device is 1000 IOs behind
Subject: [PATCH 26/31] btrfs: probe read latency if device is 1000 IOs behind
its siblings
This should solve a problem where devices get "frozen" if their read
@ -2184,7 +2184,7 @@ index 59bc6fa8b68e40..124fac989a2541 100644
From 7c11b64d08d6b1a79ba2af5167330d63a392ac18 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Thu, 17 Apr 2025 23:59:58 +0200
Subject: [PATCH 27/27] btrfs: allow a short burst of IO for probing read
Subject: [PATCH 27/31] btrfs: allow a short burst of IO for probing read
latency
If we do a probe to detect the current read latency of the device,
@ -2259,3 +2259,305 @@ index 124fac989a2541..070e26fda91f8a 100644
#endif
/* we couldn't find one that doesn't fail. Just return something
From c0007becc57f2f8fd3b12be04ff3a62b142bf436 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Sun, 20 Apr 2025 21:38:56 +0200
Subject: [PATCH 28/31] btrfs: use checkpoint latency instead of cumulative
latency
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
fs/btrfs/volumes.c | 33 +++++++++++++++++++++------------
fs/btrfs/volumes.h | 7 +++++++
2 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 070e26fda91f8a..c8a1028852b00e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6013,17 +6013,21 @@ static int btrfs_read_preferred(struct btrfs_chunk_map *map, int first,
* Compute the average latency of the device by dividing total latency by
* number of IOs.
*/
-#define BTRFS_MAX_AGE_FOR_VALID_LATENCY 1000
+#define BTRFS_MAX_AGE_FOR_VALID_LATENCY 10000
static u64 btrfs_device_read_latency(struct btrfs_device *device)
{
u64 read_wait = part_stat_read(device->bdev, nsecs[READ]);
+ u64 last_nsecs_read = (u64)atomic64_read(&device->last_nsecs_read);
unsigned long read_ios = part_stat_read(device->bdev, ios[READ]);
+ unsigned long last_ios_read = (unsigned long)atomic64_read(&device->last_ios_read);
u64 last_io_age = (u64)atomic64_read(&device->last_io_age);
u64 avg_wait = 0;
+ s64 delta_read_wait = read_wait - last_nsecs_read;
+ s64 delta_read_ios = read_ios - last_ios_read;
if (last_io_age >= 0 && last_io_age < BTRFS_MAX_AGE_FOR_VALID_LATENCY
- && read_wait && read_ios && read_wait >= read_ios)
- avg_wait = div_u64(read_wait, read_ios);
+ && delta_read_wait > 0 && delta_read_ios > 0 && delta_read_wait >= delta_read_ios)
+ avg_wait = div_u64(delta_read_wait, delta_read_ios);
return avg_wait;
}
@@ -6178,7 +6182,7 @@ static int btrfs_read_fastest_rr(struct btrfs_fs_info *fs_info,
}
#endif
-#define BTRFS_OLD_AGE_IO_BURST 20
+#define BTRFS_OLD_AGE_IO_BURST 100
static int find_live_mirror(struct btrfs_fs_info *fs_info,
struct btrfs_chunk_map *map, int first,
int dev_replace_is_ongoing)
@@ -6260,19 +6264,24 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
out:
#ifdef CONFIG_BTRFS_EXPERIMENTAL
- /* reset age of selected stripe */
- s64 current_age, new_age;
do {
- current_age = atomic64_read(&map->stripes[preferred_mirror].dev->last_io_age);
+ /* reset age of selected stripe */
+ s64 current_age;
+ struct btrfs_device *pref_dev = map->stripes[preferred_mirror].dev;
+ spin_lock(&pref_dev->latency_lock);
+
+ current_age = atomic64_read(&pref_dev->last_io_age);
if (current_age >= BTRFS_MAX_AGE_FOR_VALID_LATENCY) {
- new_age = -BTRFS_OLD_AGE_IO_BURST;
+ atomic64_set(&pref_dev->last_io_age, -BTRFS_OLD_AGE_IO_BURST);
+ atomic64_set(&pref_dev->last_nsecs_read, part_stat_read(pref_dev->bdev, nsecs[READ]));
+ atomic64_set(&pref_dev->last_ios_read, part_stat_read(pref_dev->bdev, ios[READ]));
} else if (current_age >= 0) {
- new_age = 0;
- } else {
- return preferred_mirror;
+ atomic64_set(&pref_dev->last_io_age, 0);
}
- } while (unlikely(atomic64_cmpxchg(&map->stripes[preferred_mirror].dev->last_io_age, current_age, new_age) != current_age));
+
+ spin_unlock(&pref_dev->latency_lock);
+ } while (0);
#endif
/* we couldn't find one that doesn't fail. Just return something
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index f2807a7463bf17..cea9df414d3f61 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -201,6 +201,13 @@ struct btrfs_device {
#ifdef CONFIG_BTRFS_EXPERIMENTAL
/* store an age of last read access */
atomic64_t last_io_age;
+
+ /* lock while updating values */
+ spinlock_t latency_lock;
+
+ /* last latency values for short term latency calculation */
+ atomic64_t last_nsecs_read;
+ atomic64_t last_ios_read;
#endif
};
From de919ef3e87eeed3b3d9487314b0b27221f8d868 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Sun, 20 Apr 2025 22:10:02 +0200
Subject: [PATCH 29/31] btrfs: stat latency checkpoints to get more insight
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
fs/btrfs/sysfs.c | 17 ++++++++++++++---
fs/btrfs/volumes.c | 1 +
fs/btrfs/volumes.h | 1 +
3 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index fd4583b8b27a56..f6af3de5dbed36 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -2186,15 +2186,26 @@ static ssize_t btrfs_devinfo_read_stats_show(struct kobject *kobj,
struct btrfs_device *device = container_of(kobj, struct btrfs_device,
devid_kobj);
u64 read_wait = part_stat_read(device->bdev, nsecs[READ]);
+ u64 last_nsecs_read = (u64)atomic64_read(&device->last_nsecs_read);
unsigned long read_ios = part_stat_read(device->bdev, ios[READ]);
+ unsigned long last_ios_read = (unsigned long)atomic64_read(&device->last_ios_read);
+ s64 delta_read_wait = read_wait - last_nsecs_read;
+ long delta_read_ios = read_ios - last_ios_read;
+ u64 avg_wait = 0, delta_avg_wait = 0;
- u64 avg_wait = 0;
if (read_wait && read_ios && read_wait >= read_ios)
avg_wait = div_u64(read_wait, read_ios);
- return scnprintf(buf, PAGE_SIZE, "ios %lu wait %llu avg %llu age %lld\n",
+ if (delta_read_wait > 0 && delta_read_ios > 0 && delta_read_wait >= delta_read_ios)
+ delta_avg_wait = div_u64(delta_read_wait, delta_read_ios);
+
+ return scnprintf(buf, PAGE_SIZE,
+ "cumulative ios %lu wait %llu avg %llu "
+ "checkpoint ios %ld wait %lld avg %llu "
+ "age %lld count %llu\n",
read_ios, read_wait, avg_wait,
- atomic64_read(&device->last_io_age));
+ delta_read_ios, delta_read_wait, delta_avg_wait,
+ atomic64_read(&device->last_io_age), atomic64_read(&device->checkpoints));
}
BTRFS_ATTR(devid, read_stats, btrfs_devinfo_read_stats_show);
#endif
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c8a1028852b00e..edad363b8bf067 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6273,6 +6273,7 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
current_age = atomic64_read(&pref_dev->last_io_age);
if (current_age >= BTRFS_MAX_AGE_FOR_VALID_LATENCY) {
+ atomic64_inc(&pref_dev->checkpoints);
atomic64_set(&pref_dev->last_io_age, -BTRFS_OLD_AGE_IO_BURST);
atomic64_set(&pref_dev->last_nsecs_read, part_stat_read(pref_dev->bdev, nsecs[READ]));
atomic64_set(&pref_dev->last_ios_read, part_stat_read(pref_dev->bdev, ios[READ]));
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index cea9df414d3f61..88aa0057b51d50 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -201,6 +201,7 @@ struct btrfs_device {
#ifdef CONFIG_BTRFS_EXPERIMENTAL
/* store an age of last read access */
atomic64_t last_io_age;
+ atomic64_t checkpoints;
/* lock while updating values */
spinlock_t latency_lock;
From 48e811bf475762c7d66195dfb3d60873a636f417 Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Sun, 20 Apr 2025 23:10:29 +0200
Subject: [PATCH 30/31] btrfs: rename thresholds to better match with the
checkpoint logic
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
fs/btrfs/volumes.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index edad363b8bf067..236ba74f104411 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6013,7 +6013,7 @@ static int btrfs_read_preferred(struct btrfs_chunk_map *map, int first,
* Compute the average latency of the device by dividing total latency by
* number of IOs.
*/
-#define BTRFS_MAX_AGE_FOR_VALID_LATENCY 10000
+#define BTRFS_DEVICE_LATENCY_CHECKPOINT_AGE 10000
static u64 btrfs_device_read_latency(struct btrfs_device *device)
{
u64 read_wait = part_stat_read(device->bdev, nsecs[READ]);
@@ -6025,7 +6025,7 @@ static u64 btrfs_device_read_latency(struct btrfs_device *device)
s64 delta_read_wait = read_wait - last_nsecs_read;
s64 delta_read_ios = read_ios - last_ios_read;
- if (last_io_age >= 0 && last_io_age < BTRFS_MAX_AGE_FOR_VALID_LATENCY
+ if (last_io_age >= 0 && last_io_age < BTRFS_DEVICE_LATENCY_CHECKPOINT_AGE
&& delta_read_wait > 0 && delta_read_ios > 0 && delta_read_wait >= delta_read_ios)
avg_wait = div_u64(delta_read_wait, delta_read_ios);
@@ -6182,7 +6182,7 @@ static int btrfs_read_fastest_rr(struct btrfs_fs_info *fs_info,
}
#endif
-#define BTRFS_OLD_AGE_IO_BURST 100
+#define BTRFS_DEVICE_LATENCY_CHECKPOINT_BURST_IO 100
static int find_live_mirror(struct btrfs_fs_info *fs_info,
struct btrfs_chunk_map *map, int first,
int dev_replace_is_ongoing)
@@ -6272,9 +6272,9 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
spin_lock(&pref_dev->latency_lock);
current_age = atomic64_read(&pref_dev->last_io_age);
- if (current_age >= BTRFS_MAX_AGE_FOR_VALID_LATENCY) {
+ if (current_age >= BTRFS_DEVICE_LATENCY_CHECKPOINT_AGE) {
atomic64_inc(&pref_dev->checkpoints);
- atomic64_set(&pref_dev->last_io_age, -BTRFS_OLD_AGE_IO_BURST);
+ atomic64_set(&pref_dev->last_io_age, -BTRFS_DEVICE_LATENCY_CHECKPOINT_BURST_IO);
atomic64_set(&pref_dev->last_nsecs_read, part_stat_read(pref_dev->bdev, nsecs[READ]));
atomic64_set(&pref_dev->last_ios_read, part_stat_read(pref_dev->bdev, ios[READ]));
} else if (current_age >= 0) {
From 5e140ba573925f30df00aece605fa1255d0ac50d Mon Sep 17 00:00:00 2001
From: Kai Krakow <kai@kaishome.de>
Date: Sun, 20 Apr 2025 23:12:56 +0200
Subject: [PATCH 31/31] btrfs: add a stripe ignored counter
To get some more insights, we can count how often a stripe has been
ignored relative to its neighbors. We simply increase the counter for
all candidates, then decrease it after selection.
This should show how evenly distributed one of the read balancing
algorithms is.
Signed-off-by: Kai Krakow <kai@kaishome.de>
---
fs/btrfs/sysfs.c | 5 +++--
fs/btrfs/volumes.c | 4 +++-
fs/btrfs/volumes.h | 1 +
3 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index f6af3de5dbed36..9bb159527b4be1 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -2202,10 +2202,11 @@ static ssize_t btrfs_devinfo_read_stats_show(struct kobject *kobj,
return scnprintf(buf, PAGE_SIZE,
"cumulative ios %lu wait %llu avg %llu "
"checkpoint ios %ld wait %lld avg %llu "
- "age %lld count %llu\n",
+ "age %lld count %llu ignored %lld\n",
read_ios, read_wait, avg_wait,
delta_read_ios, delta_read_wait, delta_avg_wait,
- atomic64_read(&device->last_io_age), atomic64_read(&device->checkpoints));
+ atomic64_read(&device->last_io_age), atomic64_read(&device->checkpoints),
+ atomic64_read(&device->stripe_ignored));
}
BTRFS_ATTR(devid, read_stats, btrfs_devinfo_read_stats_show);
#endif
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 236ba74f104411..22bcadb266c2b7 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6206,6 +6206,7 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
/* age each possible stripe by 1 IO */
for (int i = first; i < first + num_stripes; i++) {
atomic64_inc(&map->stripes[i].dev->last_io_age);
+ atomic64_inc(&map->stripes[i].dev->stripe_ignored);
}
#endif
@@ -6277,9 +6278,10 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
atomic64_set(&pref_dev->last_io_age, -BTRFS_DEVICE_LATENCY_CHECKPOINT_BURST_IO);
atomic64_set(&pref_dev->last_nsecs_read, part_stat_read(pref_dev->bdev, nsecs[READ]));
atomic64_set(&pref_dev->last_ios_read, part_stat_read(pref_dev->bdev, ios[READ]));
- } else if (current_age >= 0) {
+ } else if (current_age > 0) {
atomic64_set(&pref_dev->last_io_age, 0);
}
+ atomic64_dec(&pref_dev->stripe_ignored);
spin_unlock(&pref_dev->latency_lock);
} while (0);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 88aa0057b51d50..8906edbec4fd1e 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -202,6 +202,7 @@ struct btrfs_device {
/* store an age of last read access */
atomic64_t last_io_age;
atomic64_t checkpoints;
+ atomic64_t stripe_ignored;
/* lock while updating values */
spinlock_t latency_lock;