>>>>> "Guoqing" == Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx> writes: Guoqing> Hi, Guoqing> 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. Guoqing> If 'N << 9', then seems you are convert it to sector, do you actually Guoqing> mean 'N << 12'? Aren't there helpers that can be used here instead of semi-magic numbers? At the least, the 9 and 12 should be #defines with good names, or using the standard PAGE_SIZE and other defines. >> + >> + 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). Guoqing> So with the above description, the algorithm should be 2 << 12 = 8KB and Guoqing> 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. >> + Cheers, John
