GNU bug report logs - #17505
Interface inconsistency, use of intelligent defaults.

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Message #34 received at 17505 <at> debbugs.gnu.org (full text, mbox):

From: Linda Walsh <coreutils <at> tlinx.org>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 17505 <at> debbugs.gnu.org, P <at> draigBrady.com
Subject: Re: bug#17505: Interface inconsistency, use of intelligent defaults.
Date: Sat, 17 May 2014 01:23:20 -0700

Paul Eggert wrote:
> Linda Walsh wrote:
>> "125MB/s is literally impossible with a 1Gbit/s line - there will be 
> overhead"
> 
> This comment is using the usual powers-of-1000 abbreviations for both 
> the first figure (125 MB/s) and the second one (1 Gb/s), so it supports 
> the assertion that powers-of-1000 are more common in ordinary usage. 125 
> MB/s is impossible is because there is some overhead at lower protocol 
> levels, which means that you cannot possibly transfer 1 Gb of data over 
> a 1 Gb/s line in one second, i.e., you cannot possibly transfer 125 MB 
> of data over that line in one second, and that's what the comment says.
----
	I see what you are saying, but having done that measurement myself,
I can assure you the 125MB/s is exactly what 'dd' reports (using direct
I/O).  As I stated previously, when talking about bits, I see the decimal usage
as often as not.  But when people talk about timings, they want to know how
long it will take to transfer the data on their disk -- given in base2 units
to 'X'...

	Compare to 'ls', 'du', -- all give base2 units.  If you think about
it the only way it would be "impossible"  is if they though it was
125 * 2^20.  But getting 125*10^6, is relatively trivial if your overhead is
< 1% -- dd won't show it.  I could ask for clarification whether they were
using 2^20 or 10^6 for M.  But 'dd' only requires that the overhead be less
than .4 or .5% to display 125.

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