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List:       util-linux-ng
Subject:    Re: Slow USB storage device?
From:       Linus Torvalds <torvalds () linux-foundation ! org>
Date:       2010-01-21 0:34:06
Message-ID: alpine.LFD.2.00.1001201613250.13231 () localhost ! localdomain
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On Thu, 21 Jan 2010, Karel Zak wrote:
> 
>  Done. Now the code calls read() for necessary data only. Results:

Beautiful. And what a difference it makes:

	[root@EeePC util-linux-ng]# time /sbin/blkid -p /dev/sdc
	/dev/sdc: PTTYPE="dos" 
	real	0m0.269s
	user	0m0.002s
	sys	0m0.004s

	[root@EeePC util-linux-ng]# time /sbin/blkid -p /dev/sdc1
	/dev/sdc1: SEC_TYPE="msdos" VERSION="FAT12" TYPE="vfat" USAGE="filesystem" 
	
	real	0m0.271s
	user	0m0.002s
	sys	0m0.003s

so now blkid is no longer the problem.

There are still other things that are slower than I'd like, and it takes a 
total of about 8 seconds for the device to show up, but now it's one 
second of storage settling time, and 1.3s for the actual 'mount' itself to 
happen etc etc.

And part of it is that while I installed the self-compiled util-linux-ng, 
I didn't install the fixes to DeviceKit-disk, so there's two seconds of 
the slow devkit-disks-part-id and hald-probe-storage. There's at least a 
second and a half to be gained there from the trivial fadvise() thing.

But at this point, it's now just plain "that's an effing slow device", and 
no longer "the tools are just broken"

So thanks. Please do try to push this out as a release so that distros 
pick it up. And I'll do the same, and make 'delay_use' default to 0 at the 
beginning of the next merge window, to see if it really is needed. And 
we'll have a much snappier desktop.

			Linus
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