From: Eli Zaretskii <eliz@gnu.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Optimizing memory footprint of bidi code
Date: Mon, 07 Jun 2010 19:10:08 -0400 [thread overview]
Message-ID: <E1OLlSK-0005ic-Tj@fencepost.gnu.org> (raw)
In-Reply-To: <jwvwruadfaa.fsf-monnier+emacs@gnu.org> (message from Stefan Monnier on Mon, 07 Jun 2010 12:01:26 -0400)
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: emacs-devel@gnu.org
> Date: Mon, 07 Jun 2010 12:01:26 -0400
>
> > If so, this part is already taken care of. If not, how to make this
> > type smaller without losing the benefits of an enumerated type (I
> > don't want to manipulate magic values or macros)?
>
> I'm not sure what you're worried about. What's wrong with adding a ":2"
> to the field?
Nothing's wrong. I was saying that I would like to still be able to
use enumerated values and not just literal numerical constants. But I
think Tom explained that with GCC this is not a problem.
> > . struct bidi_it weighs in at 712 bytes on a 64-bit machine. Can
> > this amount of memory cause more frequent cache misses, with
> > today's cache sizes?
>
> If there's only one such struct used, then it's probably small enough
> that it doesn't matter.
There's only one such struct, it is part of struct it, the display
iterator used by redisplay. Since windows are redisplayed one at a
time, there's only one instance of struct it and correspondingly only
one instance of struct bidi_it.
There's a cache inside bidi.c that caches bidi_it states. That one
holds snapshots of struct bidi_it, but it is actively used only when
text actually needs reordering; otherwise, there's only one instance
there. When reordering _is_ needed, the number of instances there
could be potentially large, but the intent of this cache is to prevent
repeated application of UAX#9 rules to characters we already saw and
processed. This cache is on the heap.
> Of course, only measurements can give reliable answers.
I'd surely love to see some.
prev parent reply other threads:[~2010-06-07 23:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-07 14:30 Optimizing memory footprint of bidi code Eli Zaretskii
2010-06-07 15:14 ` Tom Tromey
2010-06-07 15:46 ` Andreas Schwab
2010-06-07 16:01 ` Stefan Monnier
2010-06-07 23:10 ` Eli Zaretskii [this message]
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