Excessive plugin reloads in Thunderbird 3

[Mark Peek]

I was trying to understand a different performance issue with Thunderbird 3
(3.0pre) on MacOS 10.6 when I noticed an interesting behavior using "sudo
dtruss -p pid". Just toggling between messages in the message pane will reload
the plugins for each message load. On my system this results in 200+ open
calls, re-reading files such as all the plist files and other system call
overhead. Attaching with gdb shows the opens are occurring from a call through
nsPluginHostImpl::ReloadPlugins(). This overhead might help account for the
fast churn through my laptop battery when offline. Somewhat related bugs could be:

https://bugzilla.mozilla.org/show_bug.cgi?id=438776
https://bugzilla.mozilla.org/show_bug.cgi?id=506472

I did not see this behavior on Thunderbird 2 but does show up on 3.0b4 as well
as my own 3.0pre from yesterday. Has anyone seen this as well on MacOS or
other operating systems?

Mark

[Andrew Sutherland]

On 11/05/2009 11:54 AM, Mark Peek wrote:
> I did not see this behavior on Thunderbird 2 but does show up on 3.0b4
> as well as my own 3.0pre from yesterday. Has anyone seen this as well on
> MacOS or other operating systems?

I've noticed something along these lines on linux for Thunderbird 3.
(Mainly complaints about plugins having the wrong ELFCLASS given that I
run amd64 so some things get 32-bit/64-bit unhappy.) A very cursory
investigation in bugzilla suggested that mozilla 1.9.2 had improvements
that might improve this situation, but I haven't had time to pursue it
further.

Any additional investigation you could perform would be extremely helpful.

Andrew

[Wayne Mery]

yes, there certainly is bug activity in this area. among them
https://bugzilla.mozilla.org/show_bug.cgi?id=500925 which is unclear
from the bug and patch comments whether it's in 1.9.1.5 or 1.9.1.6

[Mark Peek]

I was curious why TB2 did not show this issue. It appears that plugins were
not compiled into TB2 which would account for not showing up on the dtruss
output. I added "ac_add_options --disable-plugins" to my TB3 .mozconfig which
definitely reduced the system call overhead switching between messages due to
the plugin lookups. If I have time over the weekend I might look further at
the plugin code and delve beyond nsPluginHostImpl::ScanPluginsDirectory() to
see why the extra calls are occurring.

Mark

[Peter Weilbacher]

You could implement support for message/rfc822, so that it doesn't need to
reload the plugins at all for most messages. Bug 338762 has some details.
Peter.