On Wed, 5 Sep 2012 13:52:20 -0700, Mark Trumpold wrote:
> Hello Vyacheslav,
> 
> > Do you use NILFS as root file system?
> >
> Actually, 'nilfs' on this system is just a container that contains loop
> images, one of which is the root filesystem.  As you can see this is
> a little out of the norm, so I think I should do more homework before
> involving a lot of your time..  At this point it in not clear if TRIM is
> working at all for 'ext4' or 'nilfs' on our system.  It may be that the
> warning from 'nilfs' is legitimate.

Actually, ext4 does not emit warning even if the TRIM is not supported
by underlying block devices; it simply ignores the error status of the
discard request.

> I think it might be best for me to first find a way to test whether or
> not TRIM is working in general for a particular configuration.
> I've gone to a totally generic system with just a test 'nilfs' and 'ext4'
> partition to get some experience.  One thing I've noticed is 'ext4' does
> not complain if you mount with 'discard' on a device that does NOT
> support it -- so that's no help.
> 
> I've tried the following simple sequence:
> dd if=/dev/urandom of=tempfile bs=1M count=3
> hdparm --fibmap tempfile    <-- get start address of the file
> hdparm --read-sector [ADDRESS] /dev/sda
> rm tempfile && sync && sleep 120
> hdparm --read-sector [ADDRESS] /dev/sda   <-- should be all zero's
> 
> Got this off the Internet.  The last step NEVER returns zero's for either
> 'nilfs' or 'ext4'.
> 
> If you happen to know of a better test, that would be appreciated.

mkfs.nilfs2 issues TRIM/DISCARD by default.

With mkfs.nilfs2, you can test if the TRIM is supported on the device
if you have an empty partition:

 # dd if=/dev/urandom of=/dev/sdc2
 # mkfs -t nilfs2 -v /dev/sdc2

 where /dev/sdc1 is the empty partition in this example.

You will see the following message if TRIM is supported.

 Discard succeeded and will return 0s - skip wiping

Then, you can confirm the device is actually cleared, for exapmle,
with dd command:

 # dd if=/dev/sdc2 iflag=direct 2> /dev/null | hexdump


With regards,
Ryusuke Konishi


> Thanks for your attention.
> Best regards,
> Mark Trumpold
> 
> 
> -----Original Message-----
> From: Vyacheslav Dubeyko [mailto:[email protected]]
> Sent: Tuesday, September 04, 2012 11:31 PM
> To: Mark Trumpold
> Cc: '[email protected]'
> Subject: Re: 'nilfs' TRIM issue?
> 
> Hi Mark,
> 
> On Tue, 2012-09-04 at 16:32 -0700, Mark Trumpold wrote:
> > Greetings,
> >
> > I am seeing the following message a few minutes after booting a system:
> >
> 
> Do you use NILFS as root file system?
> 
> > "NILFS warning: error -95 on discard request, turning discards off for the 
> > device"
> >
> 
> As I can see from message that operation is not supported (-95). So, it means 
> that you try to use discard in the case of no support of it on the flash.
> 
> How did you mount NILFS (I mean mount options)?
> Could you share mount utility output without any options?
> Could you share content of your fstab file?
> 
> > We are using the "Satadom-150" flash part which does support TRIM, as
> > evidenced by 'ext4' filesystems having no issue with the mount 'discard' 
> > option.
> >
> 
> You want that it hasn't any error message when you use 'discard' mount option 
> in the case no support of it on flash. Am I correct?
> 
> With the best regards,
> Vyacheslav Dubeyko.
> 
> 
> > I am running:
> >    Debian 6.0.5
> >    Linux kernel 3.3.1
> >    Nilfs-utils 2.1.1
> >
> > Any thoughts would be greatly appreciated.
> >
> > Thanks in advance,
> > Mark Trumpold
> >
> >
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