Re: Tooltips GC overhead

[Eli Zaretskii]

> Date: Thu, 30 Jul 2015 11:05:47 +0200
> From: martin rudalics <address@hidden>
> Cc: address@hidden
> 
>  >> I suppose you didn't wait until the tooltips really showed up.
>  >
>  > No, I waited.
> 
> This is hopeless.  Evaluating
> 
> (let ((c cons-cells-consed)
>        (v vector-cells-consed))
>    (tooltip-show "foobar")
>    (message "cons: %s vector: %s"
>          (- cons-cells-consed c)
>          (- vector-cells-consed v)))
> 
> gives here "cons: 58696 vector: 9443".  Evaluating
> 
> (let ((c cons-cells-consed)
>        (v vector-cells-consed))
>    (x-show-tip "foobar")
>    (message "cons: %s vector: %s"
>          (- cons-cells-consed c)
>          (- vector-cells-consed v)))
> 
> gets me "cons: 58649 vector: 9443", so the remainder of `tooltip-show'
> is responsible for just 47 additional conses.  We can ignore that.
> 
> I suppose most of the overhead goes to x_create_tip_frame - a normal
> `make-frame' here gets me "cons: 37464 vector: 33018".  Calculating the
> tooltip position doesn't seem to add much overhead.  So the only way to
> fix this is to hide tooltip frames instead of deleting and re-creating
> them.  If this can be done properly.

According to my testing, over 80% of consing happens inside
face-spec-recalc which is called by face-set-after-frame-default on
all the known faces.

I guess your numbers above are from a non-Q session with a lot of
additional faces, because in "emacs -Q" I get "only" about 15000
conses from a single tool-tip.

So maybe one other idea is to skip faces that are obviously unused in
tip frames.

Or maybe we should just make gc-cons-threshold higher ;-)

This is not new, btw: Emacs 24.1 exhibits approximately the same
numbers, Emacs 23 conses only two thirds of that, and Emacs 22.3 one
third.