From: Tomi Ollila <tomi.ollila@iki.fi>
To: Pieter Praet <pieter@praet.org>,
	Jameson Graef Rollins <jrollins@finestructure.net>,
	Notmuch Mail <notmuch@notmuchmail.org>
Subject: Re: [PATCH] test: use dtach(1) instead of screen(1) in emacs tests.
In-Reply-To: <87hb2btsv2.fsf@praet.org>
References: <yf6mxc3ab4t.fsf@taco2.nixu.fi>
	<1320963737-1666-1-git-send-email-jrollins@finestructure.net>
	<87hb2btsv2.fsf@praet.org>
User-Agent: Notmuch/0.9+23~g556c5fa (http://notmuchmail.org) Emacs/23.3.1
	(i686-pc-linux-gnu)
Date: Fri, 11 Nov 2011 10:09:17 +0200
Message-ID: <yf6ipmrdqs2.fsf@taco2.nixu.fi>
MIME-Version: 1.0
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Precedence: list

On Fri, 11 Nov 2011 01:17:37 +0100, Pieter Praet <pieter@praet.org> wrote:
> On Thu, 10 Nov 2011 14:22:17 -0800, Jameson Graef Rollins <jrollins@finestructure.net> wrote:
> > From: Tomi Ollila <tomi.ollila@iki.fi>
> > 
> > dtach is lighter than screen and is not setuid/setgid program so
> > TMPDIR does not get reset by dynamic loader when executed.
> > 
> 
> `dtach' may be lighter than `screen', but contrary to my expectations,
> it appears to be far less efficient:
> 
> |      | original [1] | w/ screen [2] | w/ dtach [3] |
> |------+--------------+---------------+--------------|
> | real |    0m17.570s |     0m20.132s |    0m28.567s |
> | user |     0m2.453s |      0m2.593s |     0m2.753s |
> | sys  |     0m1.700s |      0m1.577s |     0m1.753s |

This sounds interesting; how were these runs measured?
Just using shell builtin time command ?

Does time measure the time of the process and it's subprocesses
or just the process. In any way 20 vs 28 second 'real' time difference
could indicate that there are more other processes running and
the context switch time affects user and system time.

Or, dtach does some stupid io things. Or screen does some advanced
optimizations. Or emacs works more effectively when TERM=screen.
Or the 'virtual' window size emacs sees is unsuitable...


> 
> > Signed-off-by: Jameson Graef Rollins <jrollins@finestructure.net>
> > ---
> > This tweaks the original patch slightly by removing the no-longer needed
> > screenrc variables.
> > 
> >  test/test-lib.sh |    5 ++---
> >  1 files changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/test/test-lib.sh b/test/test-lib.sh
> > index c81c709..c0fe037 100755
> > --- a/test/test-lib.sh
> > +++ b/test/test-lib.sh
> > @@ -50,8 +50,6 @@ TZ=UTC
> >  TERM=dumb
> >  export LANG LC_ALL PAGER TERM TZ
> >  GIT_TEST_CMP=${GIT_TEST_CMP:-diff -u}
> > -export SCREENRC=/dev/null
> > -export SYSSCREENRC=/dev/null
> >  
> >  # Protect ourselves from common misconfiguration to export
> >  # CDPATH into the environment
> > @@ -844,7 +842,8 @@ test_emacs () {
> >  	if [ -z "$EMACS_SERVER" ]; then
> >  		EMACS_SERVER="notmuch-test-suite-$$"
> >  		# start a detached screen session with an emacs server
> > -		screen -S "$EMACS_SERVER" -d -m "$TMP_DIRECTORY/run_emacs" \
> > +		TERM=xterm dtach -n "$TMP_DIRECTORY/dtach-emacs-socket-$$" \
> 
> It's worth noting that $TERM is only set to "xterm" to deceive `dtach',
> so thankfully, xterm (and all its deps) aren't actually required to run
> the tests.

Actually, emacs SIGSEGVs if there is unsuitable TERM in use. I don't know
what it originally was.

> 
> > +			"$TMP_DIRECTORY/run_emacs" \
> >  			--no-window-system \
> >  			--eval "(setq server-name \"$EMACS_SERVER\")" \
> >  			--eval '(server-start)' \
> > -- 
> > 1.7.7.1
> > 
> > _______________________________________________
> > notmuch mailing list
> > notmuch@notmuchmail.org
> > http://notmuchmail.org/mailman/listinfo/notmuch
> 
> 
> Peace
> 
> -- 
> Pieter
> 
> [1] @ commit 749abb74
> [2] @ commit 760b311b
> [3] @ commit 760b311b + id:"1320963737-1666-1-git-send-email-jrollins@finestructure.net"
> _______________________________________________
> notmuch mailing list
> notmuch@notmuchmail.org
> http://notmuchmail.org/mailman/listinfo/notmuch
> 

Tomi