From e236858243d7a8e0ac60972d2f9522146088a736 Mon Sep 17 00:00:00 2001
From: Yufen Yu <yuyufen@huawei.com>
Date: Sat, 18 Jul 2020 05:29:08 -0400
Subject: [PATCH] md/raid5: set default stripe_size as 4096
Git-commit: e236858243d7a8e0ac60972d2f9522146088a736
Patch-mainline: v5.9-rc1
References: jsc#SLE-13984
In RAID5, if issued bio size is bigger than stripe_size, it will be
split in the unit of stripe_size and process them one by one. Even
for size less then stripe_size, RAID5 also request data from disk at
least of stripe_size.
Nowdays, stripe_size is equal to the value of PAGE_SIZE. Since filesystem
usually issue bio in the unit of 4KB, there is no problem for PAGE_SIZE
as 4KB. But, for 64KB PAGE_SIZE, bio from filesystem requests 4KB data
while RAID5 issue IO at least stripe_size (64KB) each time. That will
waste resource of disk bandwidth and compute xor.
To avoding the waste, we want to make stripe_size configurable. This
patch just set default stripe_size as 4096. User can also set the value
bigger than 4KB for some special requirements, such as we know the
issued io size is more than 4KB.
To evaluate the new feature, we create raid5 device '/dev/md5' with
4 SSD disk and test it on arm64 machine with 64KB PAGE_SIZE.
1) We format /dev/md5 with mkfs.ext4 and mount ext4 with default
configure on /mnt directory. Then, trying to test it by dbench with
command: dbench -D /mnt -t 1000 10. Result show as:
'stripe_size = 64KB'
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 9805011 0.021 64.728
Close 7202525 0.001 0.120
Rename 415213 0.051 44.681
Unlink 1980066 0.079 93.147
Deltree 240 1.793 6.516
Mkdir 120 0.004 0.007
Qpathinfo 8887512 0.007 37.114
Qfileinfo 1557262 0.001 0.030
Qfsinfo 1629582 0.012 0.152
Sfileinfo 798756 0.040 57.641
Find 3436004 0.019 57.782
WriteX 4887239 0.021 57.638
ReadX 15370483 0.005 37.818
LockX 31934 0.003 0.022
UnlockX 31933 0.001 0.021
Flush 687205 13.302 530.088
Throughput 307.799 MB/sec 10 clients 10 procs max_latency=530.091 ms
-------------------------------------------------------
'stripe_size = 4KB'
Operation Count AvgLat MaxLat
----------------------------------------
NTCreateX 11999166 0.021 36.380
Close 8814128 0.001 0.122
Rename 508113 0.051 29.169
Unlink 2423242 0.070 38.141
Deltree 300 1.885 7.155
Mkdir 150 0.004 0.006
Qpathinfo 10875921 0.007 35.485
Qfileinfo 1905837 0.001 0.032
Qfsinfo 1994304 0.012 0.125
Sfileinfo 977450 0.029 26.489
Find 4204952 0.019 9.361
WriteX 5981890 0.019 27.804
ReadX 18809742 0.004 33.491
LockX 39074 0.003 0.025
UnlockX 39074 0.001 0.014
Flush 841022 10.712 458.848
Throughput 376.777 MB/sec 10 clients 10 procs max_latency=458.852 ms
-------------------------------------------------------
It show that setting stripe_size as 4KB has higher thoughput, i.e.
(376.777 vs 307.799) and has smaller latency than that setting as 64KB.
2) We try to evaluate IO throughput for /dev/md5 by fio with config:
[4KB randwrite]
direct=1
numjob=2
iodepth=64
ioengine=libaio
filename=/dev/md5
bs=4KB
rw=randwrite
[64KB write]
direct=1
numjob=2
iodepth=64
ioengine=libaio
filename=/dev/md5
bs=1MB
rw=write
The result as follow:
+ +
| stripe_size(64KB) | stripe_size(4KB)
+----------------------------------------------------+
4KB randwrite | 15MB/s | 100MB/s
+----------------------------------------------------+
1MB write | 1000MB/s | 700MB/s
The result show that when size of io is bigger than 4KB (64KB),
64KB stripe_size has much higher IOPS. But for 4KB randwrite, that
means, size of io issued to device are smaller, 4KB stripe_size
have better performance.
Normally, default value (4096) can get relatively good performance.
But if each issued io is bigger than 4096, setting value more than
4096 may get better performance.
Here, we just set default stripe_size as 4096, and we will try to
support setting different stripe_size by sysfs interface in the
following patch.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Coly Li <colyli@suse.de>
---
drivers/md/raid5.c | 5 +++++
drivers/md/raid5.h | 22 +++++++++++++++++++---
2 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 18f20f3d9664..60cfa397f2d6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6943,6 +6943,11 @@ static struct r5conf *setup_conf(struct mddev *mddev)
if (conf == NULL)
goto abort;
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+ conf->stripe_size = DEFAULT_STRIPE_SIZE;
+ conf->stripe_shift = ilog2(DEFAULT_STRIPE_SIZE) - 9;
+ conf->stripe_sectors = DEFAULT_STRIPE_SIZE >> 9;
+#endif
INIT_LIST_HEAD(&conf->free_list);
INIT_LIST_HEAD(&conf->pending_list);
conf->pending_data = kcalloc(PENDING_IO_MAX,
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index ca21f30e31da..7fb3b26a181a 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -472,9 +472,14 @@ struct disk_info {
*/
#define NR_STRIPES 256
+#define DEFAULT_STRIPE_SIZE 4096
+
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
#define STRIPE_SIZE PAGE_SIZE
#define STRIPE_SHIFT (PAGE_SHIFT - 9)
#define STRIPE_SECTORS (STRIPE_SIZE>>9)
+#endif
+
#define IO_THRESHOLD 1
#define BYPASS_THRESHOLD 1
#define NR_HASH (PAGE_SIZE / sizeof(struct hlist_head))
@@ -557,6 +562,11 @@ struct r5conf {
int raid_disks;
int max_nr_stripes;
int min_nr_stripes;
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+ unsigned long stripe_size;
+ unsigned int stripe_shift;
+ unsigned long stripe_sectors;
+#endif
/* reshape_progress is the leading edge of a 'reshape'
* It has value MaxSector when no reshape is happening
@@ -673,9 +683,15 @@ struct r5conf {
struct r5pending_data *next_pending_data;
};
-#define RAID5_STRIPE_SIZE(conf) STRIPE_SIZE
-#define RAID5_STRIPE_SHIFT(conf) STRIPE_SHIFT
-#define RAID5_STRIPE_SECTORS(conf) STRIPE_SECTORS
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
+#define RAID5_STRIPE_SIZE(conf) STRIPE_SIZE
+#define RAID5_STRIPE_SHIFT(conf) STRIPE_SHIFT
+#define RAID5_STRIPE_SECTORS(conf) STRIPE_SECTORS
+#else
+#define RAID5_STRIPE_SIZE(conf) ((conf)->stripe_size)
+#define RAID5_STRIPE_SHIFT(conf) ((conf)->stripe_shift)
+#define RAID5_STRIPE_SECTORS(conf) ((conf)->stripe_sectors)
+#endif
/* bio's attached to a stripe+device for I/O are linked together in bi_sector
* order without overlap. There may be several bio's per stripe+device, and
--
2.26.2