Re: Low redisplay performance (23 regression)

[YAMAMOTO Mitsuharu]

>>>>> On Wed, 29 Apr 2009 23:49:43 -0400, Chong Yidong <address@hidden> said:

>> Some profiling results show that many Lisp objects are constructed
>> in font_clear_prop, and that causes frequent GC triggered by Lisp
>> evaluations in redisplay such as mode/header-line calculation.
>> That would also explain why the OP doesn't observe the slowness on
>> Emacs 22 with backported face remapping.

> That's surprising.  I have experimented with making font_clear_prop
> overwrite font specs instead of allocating new ones, when possible.
> However, this does not seem to improve performance (I do not intend
> to change this for 23.1).  I think the fundamental problem does not
> lie in font_clear_prop, but in the fact that the face remapping
> code's lookup_basic_face function calls lookup_named_face ->
> merge_face_vectors far too often.

I confirmed that your latest change lowered the frequency of GC,
though I'm not sure which allocation is reduced most.

                                     YAMAMOTO Mitsuharu
                                address@hidden