Re: [PATCH v3 3/4] x86/efi: print size in binary units in efi_print_memmap

From: Andy Shevchenko
Date: Mon Jan 25 2016 - 14:28:48 EST

On Mon, Jan 25, 2016 at 8:56 PM, James Bottomley
<James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 2016-01-25 at 18:02 +0000, Elliott, Robert (Persistent Memory)
> wrote:

> Using ffs leads to precision runaway

How exactly?!

> and
> exporting an array from string_helpers.c is simply the wrong way to do
> it.

This part I didn't object.

> Since we've now spent more time arguing about this than it would take
> to do a correct patch, this is what I was thinking. It extracts the
> precision reduction core from string_helpers.c and exposes it to all
> users who want to convert to units. I added a nozeros option becuase I
> think you want it to print 1 GiB rather than 1.00 GiB for exact powers
> of two. (OK, and I fixed a bug where it will report small amounts as
> 1.00 B instead of whole number of bytes). Absent the nozero option,
> you could simply have used string_get_size(), with a block size of 1.

It's good you are doing this better, but I still vote for __ffs64(),
since it would be faster on binary units.

Also, in one version I tried to convert couple of other users which
are using only KM (in general whatever range it would be) units. Any
ideas how to modify to support them?

With Best Regards,
Andy Shevchenko