Hi. Jst curious: How come access to eMMC via PC USB mode is faster than eMMC access via N900 xterm?

kh

Please elaborate on your test methodology and test results so that proper responses can be given.

No prob. Quite simple actually.
I do some backups using backupmenu.
These days they r often around 1GB in side.

If I use N900 to make a copy of the 1GB file frm eMMC to eMMC, it seems slower compared to copying that same file frm eMMC to eMMC using PC via USB...

So, m jst curious..

kh

Well, I assume your computer is way faster than the N900, so copying/caching/etc. will be (much) faster when using the PC.

After all, there's no reason why the N900 should be faster, just because the (embedded) MMC is inserted in the N900.

Yes thanks. You're likely correct.
I suspect the same as well but thought no harm asking in case someone has a different answer.

Thing is, usually IO is the slowest part of such operation & can be 80-90 pcnt the reason for the latency.
eMMC is accessed directly by N900 while via PC, there is the USB "bottleneck"... data might need to go all the way up into PC CPU/mem buffers and all the way back down into N900. Unless there is some mechanism in N900 eMMC which takes away the need for that to happen (, where data frm eMMC goes into an N900 local buffer and then go back onto eMMC for writes, thus bypassing USB and PC altogether). But if such a mechanism exists, wldnt it be used within the kernel in N900? (would mean that N900 eMMC IO could be much faster!). Hmmm. Curious curious...

kh

The question is: what is faster? USB or the MMC interface?

I guess it depends on lots of factors, but probably the interface speed is about the same. So it comes down to which computer (N900 vs PC) can handle the data transfer faster. The N900 is not only slow, but can get very busy while caching (+ swapping), while the PC can shuffle bits around with essentially no overhead.

Of course. The N900 can't do magic. If a partition is USB-mounted on a host, it is entirely controlled by the host, meaning that even if you copy from MMC to MMC the data will go "up" to the PC and then back "down" to the MMC.

Nope

Thanks for sharing
What you said makes sense.
Again, it was jst a curiosity thing.. and for a while, I wondered whther the eMMC drivers in N900 could have a chance to get upgraded to provide superior throughputs... guess not..

kh