MMC quirks relating to performance/lifetime.
From: Andrei Warkentin <hidden>
Date: 2011-02-22 06:42:59
Also in:
linux-mmc
On Sun, Feb 20, 2011 at 9:03 AM, Arnd Bergmann [off-list ref] wrote:
From your flashbench -a run, I would guess that it uses 8 MB allocation units, although the data is not 100% conclusive there.
Because the 8MB aligned write time is significantly faster, right?
My interpretation is that it uses 16 KB pages, but can do two page-sized writes in a single access (multi-plane write). Anything smaller than a page goes to a temporary buffer first (like the Toshiba chip), but gets flushed when the next one is not contiguous. If you manage to fill the entire 16 KB page using small contiguous writes, it can do a single efficient write access instead. To confirm that 16 KB is the page size, you can try flashbench -s --scatter-span=1 --scatter-order=10 -o plot.data \ ? ? ? ?/dev/mmcblk1 -c 32 --blocksize=16384 gnuplot -p -e 'plot "plot.data" ' On most MLC flashes, this will show a pattern alternating between slow and fast pages like the one from https://lwn.net/Articles/428836/
Cool. I am attaching some graphs. The 16k sandisk shows the slow and fast page parallel lines, as does the 8k toshiba (but we knew it for the toshiba case), but the boundaries are strange for the sandisk case, and there an interesting 2mb variation in the toshiba 8k graph. What is the correct way to interpret graphs with other block sizes? A -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_8k_read_ts.png Type: image/png Size: 11238 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0006.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_8k_sandisk.png Type: image/png Size: 8964 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0007.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_16k_sandisk.png Type: image/png Size: 6853 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0008.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_32k_read_ts.png Type: image/png Size: 9471 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0009.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_32k_sandisk.png Type: image/png Size: 6790 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0010.png> -------------- next part -------------- A non-text attachment was scrubbed... Name: scatter_16k_read_ts.png Type: image/png Size: 9040 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110222/220679a1/attachment-0011.png>
