On Thu, 8 Mar 2007 [EMAIL PROTECTED] wrote:
> Hi,
>
> I'm using the g_file_storage module to make a block device /dev/sdc
> out of another block device I have as a backing store. I was pleased
> with the functionality of the module, but unfortunately it's quite a
> bit slower than I expected. g_file_storage seems to top out at around
> 3MB/sec at reads, and 6MB/sec at writes.
>
> Is it possible to speed this up at all? I am not using the module to
> test USB hardware, but as a glorified loopback device, so ideally
> getting the full speed of the backing device would be what I want.
>
> Does the dummy_hcd module only support full speed (11mbps)?
Well, dummy_hcd wasn't really meant for this sort of thing and it doesn't
try to be especially fast. Also it was never updated to take into account
the change from HZ=1000 to HZ=250 (there's even a comment about it in
the source code around line number 1265). You can speed it up quite a bit
if you add a line saying something like:
total = 1000000;
right after that comment.
> Thanks,
> Joshua
>
> Oh, and if you're curious, the reason I'm using 'g_file_storage' to
> make a loopback block device instead of 'loop' is to route around a
> stupid and unnecessary limitation in vmware -- it won't let you use
> devices that /aren't/ /dev/[hs]d* as a disk for a VM. And with
> g_file_storage, it works, successfully, it is just too slow.
You know, you could always create an entry for /dev/loop0 with a different
name. For example:
mknod /dev/hdz b 7 0
Or maybe even
ln -s /dev/loop0 /dev/hdz
Then /dev/hdz would be a loopback block device and it would work okay with
VMware.
Alan Stern
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