thanks your answer very much! I have test dd commond,but the speed is less than 200k still,if i mount the sd card not with -o sync,It will use fs cache to store data,I didn't want to use the fs cache,So i must use the -o sync option! My projest need to record 320x240 picures(infrared datas) wholely,The frame speed is 30 f/s,I have to save 15 f/s at least! if i just used c function fwrite() to save data to sd card,I find my program will been blocked,and the capture pictures(infrared datas) will been lost much! It is prohibited!
2009-08-04 zuowenping 发件人： Koen Kooi 发送时间： 2009-08-04 14:32:34 收件人： davinci-linux-open-source@linux.davincidsp.com 抄送： 主题： Re: why is the sd/mmc so slowly in writing about dm355? On 03-08-09 13:08, zuowenping wrote: > I am testing the speed of sd/mmc in dm355 which using kernel 2.6.18. > > bash-3.00# mount /dev/mmcblk0p1 /mnt -o sync > bash-3.00# time cp /tmp/ramdisk.img.gz /mnt/ That's not testing how fast the sd card is, that's testing how sucky the interaction between the block and fs schedulers is for sync mounts. A better test would be to do 'hdparm -tT /dev/mmcblk0' or 'dd if=/dev/mmcblk0 of=/dev/null bs=512k'. regards, Koen _______________________________________________ Davinci-linux-open-source mailing list Davinci-linux-open-source@linux.davincidsp.com http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
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