linux-kernel - Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

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Message-Id: <201007171100.31186.arnd@arndb.de>
Date:	Sat, 17 Jul 2010 11:00:30 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mark Harris <mhlk@....us>
Cc:	David Howells <dhowells@...hat.com>,
	Steve French <smfrench@...il.com>, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org,
	samba-technical@...ts.samba.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

On Saturday 17 July 2010 07:51:30 Mark Harris wrote:
> David Howells wrote:
> > With a 2:2 split between exponent
> > (tv_gran_units) and mantissa (tv_granularity), you can do:
> > 
> >       UNIT            SECONDS/UNIT    EXPONENT        MANTISSA
> >       nanoseconds     0.000000001     -9              1
> >       microseconds    0.000001        -6              1
> >       millseconds     0.001           -3              1
> >       seconds         1               0               1
> >       minutes         60              1               6
> >       hours           3600            2               36
> >       days            86400           2               864
> >       weeks           604800          2               6048
> 
> At least for the in-tree filesystems, I do not see any that keep
> timestamps with a granularity larger than 2s.  For that, a simple
> 32-bit tv_granularity in nanoseconds (not limited to 1e9) would
> suffice, and there is no need for the complexity of dealing with
> a separate exponent.

Yes, good point. That would indeed be a significant simplification.

	Arnd
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