From: Dmitry Antipov <dmantipov@yandex.ru>
To: Thien-Thi Nguyen <ttn@gnuvola.org>
Cc: emacs-devel@gnu.org
Subject: Re: Note on 109327
Date: Wed, 01 Aug 2012 08:34:55 +0400 [thread overview]
Message-ID: <5018B1EF.8010909@yandex.ru> (raw)
In-Reply-To: <87obmv1u3i.fsf@zigzag.favinet>
On 08/01/2012 01:47 AM, Thien-Thi Nguyen wrote:
> > I think to do this well you will need separate macros for getting
> > and setting.
>
> Sure, but it's almost impossible to do this at once.
>
> Why?
As an exercise, try this for 'contents' member of Lisp_Vector.
>
> At the very beginning, it's possible to "overestimate" barrier
> assuming that each XVAR (obj, field) changes FIELD in OBJ; in the
> future, reads and writes may be separated, thus giving a precise
> write barrier.
>
> I think you're saying that you prefer to do:
>
> a1. substitute object access (whether LHS or RHS) w/ XVAR (obj, field)
> a2. distinguish LHS (which could benefit from optimization) from RHS
> a3. substitue LHS ‘XVAR (...) = value’ w/ SETVAR (obj, field, value)
>
> instead of:
>
> b1. distinguish LHS (which could benefit from optimization) from RHS
> b2. substitute LHS object access w/ SETVAR (obj, field, value)
> b3. substitute RHS object access w/ XVAR (obj, field)
>
> Is my understanding correct?
a1) is definitely the first, since this gives a base to design an
"overestimated" write barrier (each XVAR (obj, field) issues the
barrier). Next, it should be possible to implement generational
pass for GC (which collects only an objects changed since the last
collection). This is expected to be very inefficient because write
barrier is hugely overestimated. Finally, it's time for a3) or b2),
i.e. removing the barrier from XVAR (obj, field) and installing it
only at XSETVAR (obj, field, value), thus reducing "overestimation"
of the barrier.
Dmitry
next prev parent reply other threads:[~2012-08-01 4:34 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-31 12:38 Note on 109327 Dmitry Antipov
2012-07-31 13:13 ` Dan Nicolaescu
2012-07-31 13:25 ` Dmitry Antipov
2012-07-31 13:33 ` Tom Tromey
2012-07-31 13:50 ` Dmitry Antipov
2012-07-31 21:47 ` Thien-Thi Nguyen
2012-08-01 4:34 ` Dmitry Antipov [this message]
2012-07-31 13:54 ` Juanma Barranquero
2012-07-31 17:04 ` Eli Zaretskii
2012-07-31 17:17 ` Juanma Barranquero
2012-07-31 17:35 ` joakim
2012-07-31 17:56 ` Dmitry Antipov
2012-07-31 17:42 ` Dmitry Antipov
2012-07-31 18:06 ` Refactoring in Emacs (was: Note on 109327) Eli Zaretskii
2012-08-01 4:14 ` Refactoring in Emacs Dmitry Antipov
2012-08-01 11:41 ` Refactoring in Emacs : CEDET Eric M. Ludlam
2012-08-01 14:50 ` Eli Zaretskii
2012-08-01 23:42 ` Eric Ludlam
2012-08-01 22:41 ` Refactoring in Emacs Richard Stallman
2012-08-01 14:05 ` Jason Rumney
2012-07-31 15:16 ` Note on 109327 Jan Djärv
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