From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel @ vger . kernel . org"
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 3/4] x86/efi: print size in binary units in efi_print_memmap
Date: Mon, 25 Jan 2016 12:18:55 -0800 [thread overview]
Message-ID: <1453753135.2363.60.camel@HansenPartnership.com> (raw)
In-Reply-To: <CAHp75VeXHoyOgFSb4vzWBmELH_yJx1mSN+quxue=tSZCh5sTXw@mail.gmail.com>
On Mon, 2016-01-25 at 22:01 +0200, Andy Shevchenko wrote:
> On Mon, Jan 25, 2016 at 9:45 PM, James Bottomley
> <James.Bottomley@hansenpartnership.com> wrote:
> > On Mon, 2016-01-25 at 21:28 +0200, Andy Shevchenko wrote:
> > > On Mon, Jan 25, 2016 at 8:56 PM, James Bottomley
> > > <James.Bottomley@hansenpartnership.com> wrote:
> > > > On Mon, 2016-01-25 at 18:02 +0000, Elliott, Robert (Persistent
> > > > Memory)
> > > > wrote:
> > >
> > > > Using ffs leads to precision runaway
> > >
> > > How exactly?!
> >
> > Off by one. A size of 0xffffffffffffffff prints
> > 18446744073709551615 B
> > rather than 20 GiB.
>
> Because it's not a 20 GiB. It's exactly 20 GiB - 1 B.
>
> AFAIU, the intention was to show _exact_ size.
I think that's a bad idea: The range shows you the exact stuff in hex,
so all the information is present if you want precision. What's
printed in brackets is for humans to read. I'd have to reach for a
calculator to work out that 18446744073709551615 is actually around 20
GiB.
James
WARNING: multiple messages have this Message-ID (diff)
From: James Bottomley <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org>
To: Andy Shevchenko
<andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: "Elliott,
Robert (Persistent Memory)"
<elliott-ZPxbGqLxI0U@public.gmane.org>,
Andy Shevchenko
<andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
Matt Fleming
<matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"H . Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Rasmus Villemoes
<linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
"linux-kernel @ vger . kernel . org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH v3 3/4] x86/efi: print size in binary units in efi_print_memmap
Date: Mon, 25 Jan 2016 12:18:55 -0800 [thread overview]
Message-ID: <1453753135.2363.60.camel@HansenPartnership.com> (raw)
In-Reply-To: <CAHp75VeXHoyOgFSb4vzWBmELH_yJx1mSN+quxue=tSZCh5sTXw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Mon, 2016-01-25 at 22:01 +0200, Andy Shevchenko wrote:
> On Mon, Jan 25, 2016 at 9:45 PM, James Bottomley
> <James.Bottomley-JuX6DAaQMKPCXq6kfMZ53/egYHeGw8Jk@public.gmane.org> wrote:
> > On Mon, 2016-01-25 at 21:28 +0200, Andy Shevchenko wrote:
> > > On Mon, Jan 25, 2016 at 8:56 PM, James Bottomley
> > > <James.Bottomley-JuX6DAaQMKPCXq6kfMZ53/egYHeGw8Jk@public.gmane.org> wrote:
> > > > On Mon, 2016-01-25 at 18:02 +0000, Elliott, Robert (Persistent
> > > > Memory)
> > > > wrote:
> > >
> > > > Using ffs leads to precision runaway
> > >
> > > How exactly?!
> >
> > Off by one. A size of 0xffffffffffffffff prints
> > 18446744073709551615 B
> > rather than 20 GiB.
>
> Because it's not a 20 GiB. It's exactly 20 GiB - 1 B.
>
> AFAIU, the intention was to show _exact_ size.
I think that's a bad idea: The range shows you the exact stuff in hex,
so all the information is present if you want precision. What's
printed in brackets is for humans to read. I'd have to reach for a
calculator to work out that 18446744073709551615 is actually around 20
GiB.
James
next prev parent reply other threads:[~2016-01-25 20:19 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-23 14:55 [PATCH v3 0/4] x86/efi: use binary units when printing Andy Shevchenko
2016-01-23 14:55 ` [PATCH v3 1/4] lib/string_helpers: export string_units_{2,10} for others Andy Shevchenko
2016-01-23 16:14 ` James Bottomley
2016-01-23 16:14 ` James Bottomley
2016-01-23 16:58 ` Andy Shevchenko
2016-01-23 16:58 ` Andy Shevchenko
2016-01-23 14:55 ` [PATCH v3 2/4] lib/string_helpers: fix indentation in few places Andy Shevchenko
2016-01-23 14:55 ` [PATCH v3 3/4] x86/efi: print size in binary units in efi_print_memmap Andy Shevchenko
2016-01-23 16:44 ` James Bottomley
2016-01-23 16:44 ` James Bottomley
2016-01-23 17:18 ` Andy Shevchenko
2016-01-23 17:18 ` Andy Shevchenko
2016-01-23 18:03 ` James Bottomley
2016-01-23 18:03 ` James Bottomley
2016-01-25 8:31 ` Andy Shevchenko
2016-01-25 8:31 ` Andy Shevchenko
2016-01-25 15:25 ` James Bottomley
2016-01-25 15:25 ` James Bottomley
2016-01-23 18:12 ` James Bottomley
2016-01-23 18:12 ` James Bottomley
2016-01-23 20:29 ` One Thousand Gnomes
2016-01-23 20:43 ` H. Peter Anvin
2016-01-23 20:43 ` H. Peter Anvin
2016-01-25 18:02 ` Elliott, Robert (Persistent Memory)
2016-01-25 18:02 ` Elliott, Robert (Persistent Memory)
2016-01-25 18:56 ` James Bottomley
2016-01-25 18:56 ` James Bottomley
2016-01-25 19:28 ` Andy Shevchenko
2016-01-25 19:28 ` Andy Shevchenko
2016-01-25 19:45 ` James Bottomley
2016-01-25 19:45 ` James Bottomley
2016-01-25 20:01 ` Andy Shevchenko
2016-01-25 20:01 ` Andy Shevchenko
2016-01-25 20:18 ` James Bottomley [this message]
2016-01-25 20:18 ` James Bottomley
2016-01-25 20:37 ` Elliott, Robert (Persistent Memory)
2016-01-25 20:37 ` Elliott, Robert (Persistent Memory)
2016-01-26 11:50 ` Matt Fleming
2016-01-26 11:59 ` Andy Shevchenko
2016-01-26 11:59 ` Andy Shevchenko
2016-01-28 9:29 ` Matt Fleming
2016-01-28 9:29 ` Matt Fleming
2016-01-28 11:15 ` Andy Shevchenko
2016-01-28 11:15 ` Andy Shevchenko
2016-01-25 20:44 ` James Bottomley
2016-01-25 20:44 ` James Bottomley
2016-01-23 14:55 ` [PATCH v3 4/4] x86/efi: Use proper units in efi_find_mirror() Andy Shevchenko
2016-01-23 14:55 ` Andy Shevchenko
2016-01-23 16:34 ` [PATCH v3 0/4] x86/efi: use binary units when printing James Bottomley
2016-01-23 16:34 ` James Bottomley
2016-01-23 17:20 ` Andy Shevchenko
2016-01-23 17:20 ` Andy Shevchenko
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