On 2020/5/27 21:54, Guoqing Jiang wrote:
Hi,
On 5/27/20 3:19 PM, Yufen Yu wrote:
+config MD_RAID456_STRIPE_SHIFT
+ int "RAID4/RAID5/RAID6 stripe size shift"
+ default "1"
+ depends on MD_RAID456
+ help
+ When set the value as 'N', stripe size will be set as 'N << 9',
+ which is a multiple of 4KB.
If 'N << 9', then seems you are convert it to sector, do you actually mean 'N << 12'?
+
+ The default value is 1, that means the default stripe size is
+ 4096(1 << 9). Just setting as a bigger value when PAGE_SIZE is
+ bigger than 4096. In that case, you can set it as 2(8KB),
+ 4(16K), 16(64K).
So with the above description, the algorithm should be 2 << 12 = 8KB and so on.
+
+ When you try to set a big value, likely 16 on arm64 with 64KB
+ PAGE_SIZE, that means, you know size of each io that issued to
+ raid device is more than 4096. Otherwise just use default value.
+
+ Normally, using default value can get better performance.
+ Only change this value if you know what you are doing.
+
+
config MD_MULTIPATH
tristate "Multipath I/O support"
depends on BLK_DEV_MD
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index f90e0704bed9..b25f107dafc7 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -472,7 +472,9 @@ struct disk_info {
*/
#define NR_STRIPES 256
-#define STRIPE_SIZE PAGE_SIZE
+#define CONFIG_STRIPE_SIZE (CONFIG_MD_RAID456_STRIPE_SHIFT << 9)
+#define STRIPE_SIZE \
+ (CONFIG_STRIPE_SIZE > PAGE_SIZE ? PAGE_SIZE : CONFIG_STRIPE_SIZE)
If I am not misunderstand, you need to s/9/12/ above.
Oh yeah, thanks a lot for catching this. Sorry for this obvious error.
It show be 12, then STRIPE_SIZE can be multiple of 4KB, as Liu Song suggested.
Thanks,
Yufen,
