On Tue, 21 Sep 2004, Kyle Harris wrote:

> While debugging my new hcd 2.6.8.1 HCD on PXA platform I get the following 
> error:
> 
> usb-storage: page allocation failure. order:0, mode:0x20
> 
> I've checked for memory leaks in the hcd but pretty sure there are none 
> (count mallocs and frees). I can copy small files to the usbdrive and see 
> free memory go down. But as soon as I umount the device, available memory 
> comes back. Is it normal to see this error?

This message indicates you have run out of free memory, right?  No, it's 
not usual, at least not on desktop machines with lots of memory and swap 
space.  It might end up being a lot more common on PXA platforms.

usb-storage (or rather, the scatter-gather library that usb-storage calls) 
needs to allocate memory to do its work.  It has to use SLAB_NOIO because 
there might be a swap partition on the USB storage device -- we wouldn't 
want a transfer to block waiting for memory to be swapped out to the 
device that's blocked!  So it's vulnerable to low-memory conditions.

The memory usage that you see while the device is mounted doesn't come 
from usb-storage; it must come from the filesystem code.

Alan Stern



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