Subject: bug#28695: 26.0.60; Rendering lag spikes caused by double-buffering on Linux

From: Dmitry Gutov <[email-masked]>
Date: Thu, 5 Oct 2017 16:36:53 +0300

On 10/4/17 2:21 PM, Bryan Gilbert wrote:

>> Isn't it strange that only some people see these problems, while
>> others (the majority?) are very happy with double-buffering?  Could it
>> be that the problems are triggered by some specific system
>> configurations or Emacs build-time features?  If so, we could perhaps
>> turn it off only for those configurations, because people who are
>> happy with this are extremely happy, and will probably be disappointed
>> if we just turn it off globally.

Eli, perhaps it would be wise to ask the reporter if he'd like it to be 
turned off by default, if this problem can't be fixed in time.

Personally, I can stand a few minor glitches, given that double 
buffering saves me from flickering, which has been an annoyance for years.

> I'm currently using a Dell XPS 15 laptop with a 4K display and running
> at a resolution of 3840x2160.

Bryan, which revision/year is it? I also have an XPS 15 (with Skylake 
CPU) with 4K resolution, and at worst, I see the minor stutters you show 
in the 1080p video (after adding the advice, yes).

Ubuntu 17.04 with Unity 7 here.

I wasn't able to compare with the revision before double buffering, 
though: after checking out c29071587c64efb30792bd72248d3c791abd9337^, 
./autogen.sh says:

Checking whether you have the necessary tools...
(Read INSTALL.REPO for more details on building Emacs)
Checking for autoconf (need at least version 2.65)...
ok
Checking for automake (need at least version 1.11)...
ok
Your system has the required tools.
Running 'autoreconf -fi -I m4' ...
/usr/bin/m4:aclocal.m4:9: cannot open `m4/count-leading-zeros.m4': No 
such file or directory
/usr/bin/m4:aclocal.m4:12: cannot open `m4/d-type.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:20: cannot open `m4/explicit_bzero.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:46: cannot open `m4/localtime-buffer.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:52: cannot open `m4/minmax.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:55: cannot open `m4/mode_t.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:58: cannot open `m4/nstrftime.m4': No such file 
or directory
/usr/bin/m4:aclocal.m4:60: cannot open `m4/open-cloexec.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:61: cannot open `m4/open.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:103: cannot open `m4/unlocked-io.m4': No such 
file or directory
autom4te: /usr/bin/m4 failed with exit status: 1
/usr/bin/m4:aclocal.m4:9: cannot open `m4/count-leading-zeros.m4': No 
such file or directory
/usr/bin/m4:aclocal.m4:12: cannot open `m4/d-type.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:20: cannot open `m4/explicit_bzero.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:46: cannot open `m4/localtime-buffer.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:52: cannot open `m4/minmax.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:55: cannot open `m4/mode_t.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:58: cannot open `m4/nstrftime.m4': No such file 
or directory
/usr/bin/m4:aclocal.m4:60: cannot open `m4/open-cloexec.m4': No such 
file or directory
/usr/bin/m4:aclocal.m4:61: cannot open `m4/open.m4': No such file or 
directory
/usr/bin/m4:aclocal.m4:103: cannot open `m4/unlocked-io.m4': No such 
file or directory
autom4te: /usr/bin/m4 failed with exit status: 1
autoreconf: /usr/bin/autoconf failed with exit status: 1