Re: slow sync of fat 32 hotplugged devices

[Greg KH <greg@kroah.com>]

On Thu, Dec 15, 2005 at 07:28:09PM +0100, Patrick Fritzsch wrote:
> Hallo,
> I checked out suse10 lately and discovered some annoying behaviour in
> hotplugging an USB Stick.
> 
> It seems that the hal daemon mounts a usbstick in fat32 mode, where
> default the sync option ist on. Actually this is a nice behaviour,
> because a cp to the stick should last so long until the file was
> completly written.

This is a HAL issue, just have it mount without sync enabled and your
speed will return.

> Actually the performance is very bad. A 200 MB file needs around 10
> Minutes in sync mode, while it needs around 1 Minute in not synchronous
> mode + executing a sync command later.
> 
> I guess that the kernel checks after every block of the file, which is
> written, if the stick has really written it, which leads to such a big
> slowdown. There are already lots of comments of this in the web, where
> the solution is always to disable the sync mode in the hal daemon device
> files.
> 
> Wouldnt it be a nice behaviour, if you could mount a file in a new sync
> mode, where it isnt synchronized during writing a file, only when a
> close ioctl command was executed on a filehandle?
> sync writing to hotplugged devices would be a lot faster then.

Yes it would, and I'm pretty sure people are already working on this :)

But if you have some patches that enable this functionality already,
please post them.

thanks,

greg k-h