LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Austin S Hemmelgarn <ahferroin7@gmail.com>
To: "Theodore Ts'o" <tytso@mit.edu>,
	Martin Tournoij <martin@arp242.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC] The SIGINFO signal from BSD
Date: Wed, 05 Nov 2014 15:30:30 -0500
Message-ID: <545A88E6.2060509@gmail.com> (raw)
In-Reply-To: <20141105201404.GH27083@thunk.org>

[-- Attachment #1: Type: text/plain, Size: 1842 bytes --]

On 2014-11-05 15:14, Theodore Ts'o wrote:
> On Wed, Nov 05, 2014 at 02:31:12PM -0500, Austin S Hemmelgarn wrote:
>>>
>>> SIGINFO prints the status of the process to the terminal; BSD cp, for example,
>>> shows show much data it's copied:
>>>
>>>      $ cp large_file /dev/null
>>>      <press ^t>
>>>      load: 1.39  cmd: cp 85837 [running] 3.91r 0.00u 0.98s 8% 2340k
>>>      large_file -> /dev/null  15%
>>>
>>> As you see, it shows the current load, pid, process status, memory usage, as
>>> well as how much of the file has been copied. Many other BSD tools print similar
>>> statistics (mv, tar, dd, sleep, fetch, etc.).
>>
>> You have to understand however, that the reason that SIGINFO works like that
>> on *BSD is that the kernel and core userspace are developed together,
>> whereas on Linux, they are maintained entirely separately. Outside of core
>> userspace components, using SIGINFO that way on *BSD is just convention.
>
> Actually, the first line:
>
> 	load: 1.39  cmd: cp 85837 [running] 3.91r 0.00u 0.98s 8% 2340k
>
> is actually printed by the kernel.  It's actually something which is
> implemented in the BSD N_TTY line displine.  We never implemented it
> (at least when I was maintaining the tty subsystem) mostly out of
> laziness.  Part of the reason is that the main reason was that main
> reason why people (at least systems programmers / kernel programers
> like me) used ^T was to debug an apparently hung system, and for
> Linux, we had a much more powerful system using the magic-sysrq key.
>
I hadn't realized that it was actually the kernel printing that, but 
then I've never really looked all that deep into the BSD source code.
Ironically, the magic-sysrq key is one of the big reasons I've 
personally chosen to stay with Linux over any of the BSD derivatives. :)


[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 2455 bytes --]

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-05 15:17 Martin Tournoij
2014-11-05 19:31 ` Austin S Hemmelgarn
2014-11-05 20:14   ` Theodore Ts'o
2014-11-05 20:30     ` Austin S Hemmelgarn [this message]
2014-11-05 22:13     ` Martin Tournoij
2014-11-06 13:19       ` Pádraig Brady
2014-11-10 14:22     ` One Thousand Gnomes
2014-11-10 14:34       ` Martin Tournoij
2014-11-10 16:16       ` Austin S Hemmelgarn
2014-11-23  9:48       ` Pavel Machek

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=545A88E6.2060509@gmail.com \
    --to=ahferroin7@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=martin@arp242.net \
    --cc=tytso@mit.edu \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org linux-kernel@archiver.kernel.org
	public-inbox-index lkml


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox