On Saturday 25 February 2012, Andrew Bradford wrote:
On Thu, Feb 23, 2012, at 09:37 PM, Arnd Bergmann wrote:
On Monday 20 February 2012, Andrew Bradford wrote:
andrew@bigbox:~/flashbench$ sudo sfdisk -uS -l /dev/sdc
Disk /dev/sdc: 1890 cylinders, 128 heads, 32 sectors/track Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System/dev/sdc1 * 8192 7741439 7733248 c W95 FAT32 (LBA) /dev/sdc2 0 - 0 0 Empty /dev/sdc3 0 - 0 0 Empty /dev/sdc4 0 - 0 0 Empty
factor $[(7741439 + 1) / 2] 3870720: 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 5 7
This could be either 945 * 4 MB or 630 * 6 MB
This isn't the partition map that the card came with. I had to repartition it because I accidentally blew away the MBR. I would think that matters for your assessment.
Ah, well spotted. I normally use 'fdisk -l -u /dev/sdc' to find the exact size, and I had not realized that you used sfdisk on a somewhat addly partitioned device.
[andrew@mythdvr flashbench]$ sudo fdisk -l /dev/sdc | grep Disk Disk /dev/sdc: 3965 MB, 3965190144 bytes Disk identifier: 0x00000000 [andrew@mythdvr flashbench]$ factor 3965190144 3965190144: 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 2521
That 2^18 in the factor, would that indicate 512KiB making 7563 512 KiB blocks? Or 2521 1.5MiB blocks?
The 1.5MiB blocks would make sense for SanDisk, right?
Yes, this sounds right.
Does partitioning really matter for running flashbench if I'm doing it on the entire device and not within a partition? I know the partitioning matters for aligning the partition to the underlying flash for use as a filesystem, but I can't easily see how it matters for flashbench other than to get an idea of the manufacturer's partitioning to see the erase block size.
No, the partition does not matter at all. Only the size matters here.
andrew@bigbox:~/flashbench$ sudo ./flashbench -a /dev/sdc --blocksize=1024 --count=100 ## 2MiB erase block ## 8KiB pages? hard to see
I would rerun this with --blocksize=3072, there might be more to see if in case this has a multiple of 3 in it.
[andrew@mythdvr flashbench]$ sudo ./flashbench -a /dev/sdc --blocksize=3072 --count=100 align 805306368 pre 1.05ms on 1.16ms post 1.1ms diff 87.9µs align 402653184 pre 1.06ms on 1.12ms post 1.03ms diff 74.7µs align 201326592 pre 997µs on 1.1ms post 1ms diff 96.5µs align 100663296 pre 1.12ms on 1.21ms post 1.1ms diff 97.1µs align 50331648 pre 1.15ms on 1.27ms post 1.15ms diff 124µs align 25165824 pre 1.13ms on 1.23ms post 1.14ms diff 92.6µs align 12582912 pre 1.13ms on 1.23ms post 1.13ms diff 98.4µs align 6291456 pre 1.13ms on 1.27ms post 1.13ms diff 136µs ## align 3145728 pre 1.14ms on 1.18ms post 1.15ms diff 35.1µs align 1572864 pre 1.13ms on 1.19ms post 1.12ms diff 64.3µs align 786432 pre 1.13ms on 1.16ms post 1.11ms diff 34.4µs align 393216 pre 1.15ms on 1.13ms post 1.13ms diff -6419ns align 196608 pre 1.13ms on 1.15ms post 1.12ms diff 22.6µs align 98304 pre 1.12ms on 1.15ms post 1.15ms diff 15.7µs align 49152 pre 1.16ms on 1.18ms post 1.18ms diff 10.4µs align 24576 pre 1.11ms on 1.1ms post 1.13ms diff -23212n align 12288 pre 1.17ms on 1.13ms post 1.16ms diff -26969n align 6144 pre 1.14ms on 1.12ms post 1.11ms diff -9644ns
There's the 6 MB.
Yes, that's what it looks like.
With the numbers like this, my guess is that it can in fact do 9 erase blocks of some other size, possibly as small as 512KB using the sandisk trick where they write all bits at once to turn an 1.5MB TLC block into a 0.5MB SLC block.
Maybe you can try playing with the offset to find the correct erase block size. If 512KB gives you the full 12MB/s in linear mode with open-au-nr=9, try misaligning this:
# natural alignment (start at default of 16MB) sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] \ --blocksize=65536 --open-au-nr=9
[andrew@mythdvr flashbench]$ sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] --blocksize=$[4*1024] --open-au-nr=1 512KiB 13.3M/s 256KiB 12.2M/s 128KiB 12.3M/s 64KiB 12.4M/s 32KiB 12.4M/s 16KiB 11.4M/s 8KiB 9.09M/s 4KiB 6.58M/s
[andrew@mythdvr flashbench]$ sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] --blocksize=$[4*1024] --open-au-nr=9 512KiB 11.6M/s 256KiB 11.7M/s 128KiB 11M/s 64KiB 9.77M/s 32KiB 8.25M/s 16KiB 6.2M/s 8KiB 3.36M/s 4KiB 1.52M/s
4KiB is about half the speed of 8KiB is about half the speed of 16KiB.
Would this be any indicator that the page size is 16KiB?
Yes, exactly
With erasesize of 512KiB, 10 open-au is still very slow.
Right, that was expected.
# offset by one erase block, should still be fast sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] \ --blocksize=65536 --open-au-nr=9 --offset=$[18 * 1024 * 1024 + 512 * 1024]
[andrew@mythdvr flashbench]$ sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] --blocksize=$[8*1024] --open-au-nr=9 --offset=$[18*1024*1024+512*1024] 512KiB 12.2M/s 256KiB 11M/s 128KiB 9.98M/s 64KiB 9.87M/s 32KiB 7.62M/s 16KiB 6.16M/s 8KiB 3.26M/s
Ok, no difference to other offset. good.
# offset by half an erase block, only fast if actual block size is larger than 512KB sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] \ --blocksize=65536 --open-au-nr=9 --offset=$[18 * 1024 * 1024 + 256 * 1024]
[andrew@mythdvr flashbench]$ sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] --blocksize=$[8*1024] --open-au-nr=9 --offset=$[18*1024*1024+256*1024] 512KiB 12M/s 256KiB 7.93M/s 128KiB 7.46M/s 64KiB 7.11M/s 32KiB 6.25M/s 16KiB 4.89M/s 8KiB 2.95M/s
Reasonably fast, especially compared to the next test.
It is noticeably slower than the one before though, which indicates that it's not all the same the drive.
# offset by half an erase block backwards, should be slow sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] \ --blocksize=65536 --open-au-nr=9 --offset=$[18 * 1024 * 1024 - 256 * 1024]
[andrew@mythdvr flashbench]$ sudo ./flashbench /dev/sdc --open-au --erasesize=$[512*1024] --blocksize=$[8*1024] --open-au-nr=9 --offset=$[18*1024*1024-256*1024] 512KiB 5.77M/s 256KiB 2.32M/s 128KiB 2.28M/s 64KiB 2.26M/s 32KiB 2.16M/s 16KiB 1.99M/s 8KiB 2.19M/s
Ok. So 18MB is definitely an erase block boundary. The numbers here are not as slow as I had expected, but basically it does what's expected here.
I found that flashbench doesn't like erasesizes that aren't powers of 2, such as I can't do --erasesize=$[3*512*1024].
Yes, I've never managed to implement that. You can do it when you also set the blocksize to a multiple of three, as in
sudo ./flashbench /dev/sdc --open-au --erasesize=$[3* 512*1024] --blocksize=$[12*1024] --open-au-nr=9 --offset=$[18*1024*1024]
but that's not always ideal either, because small blocks will not be a multiple of the page size then.
One thing I usually try when I'm not entirely sure about the erase block size is to play a bit more with the offset. You have established that 18MB is a boundary, as it normally is for these 3-bit-per-cell chips. If the erase size is 1.5MB, the next boundary is at 19.5MB, while for a 6 MB erase size, it would be at 24 MB.
The offsets that I would try therefore are
19MB (should be fast) 19.25MB (should be either like 17.75 or like 18.25, which you've both tried before) 23.75 (should be like 17.75)
Arnd