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Re: Low redisplay performance (23 regression)

From: YAMAMOTO Mitsuharu
Subject: Re: Low redisplay performance (23 regression)
Date: Thu, 30 Apr 2009 15:27:02 +0900
User-agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shij┼Ź) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI)

>>>>> 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

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