From: Dmitry Antipov <dmantipov@yandex.ru>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: emacs-devel@gnu.org
Subject: Re: Proposal: block-based vector allocator
Date: Fri, 01 Jun 2012 09:15:59 +0400 [thread overview]
Message-ID: <4FC8500F.6000109@yandex.ru> (raw)
In-Reply-To: <4FC79188.4070200@cs.ucla.edu>
On 05/31/2012 07:43 PM, Paul Eggert wrote:
> Have you done some performance analysis on typical 64- and 32-bit hosts?
Sure.
> Has this been published somewhere? Should be in the ChangeLog entry or whatnot.
I'll post it here, just after making them readable and comparable.
>> + /* On a 32-bit system, rounding up vector size (in bytes) up
>> + to mult-of-8 helps to maintain mult-of-8 alignment. */
>> + roundup_size = 8
>
> This alignment is needed only if USE_LSB_TAG, right? If so, the
> roundup should occur only on such hosts.
It looks like you miss the core idea behind this code.
The rounding is not just to force alignment. For the block-allocated vectors,
this code rounds each possible vector size (in bytes) up to nearest
mult-of-roundup_size bytes, and then uses (size / roundup_size) as an index
into vector_free_lists. I believe this is the most natural way for both 32
and 64-bit systems with USE_LSB_TAG since it guarantees expected alignment
by design. On non-USE_LSB_TAG system, roundup_size is orthogonal to pointer
values (roundup_size can't be less than sizeof (Lisp_Object), of course).
For example, 32-bit system (non-wide-int, i.e. sizeof (Lisp_Object) == 4)
without USE_LSB_TAG is expected to work with roundup_size = 4, but I can't
test this and have no ideas why it's worth trying at all.
Dmitry
next prev parent reply other threads:[~2012-06-01 5:15 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-06 5:22 Proposal: block-based vector allocator Dmitry Antipov
2011-12-06 13:35 ` Stefan Monnier
2011-12-06 15:14 ` Dmitry Antipov
2011-12-06 19:39 ` Stefan Monnier
2011-12-07 5:05 ` Dmitry Antipov
2011-12-07 12:27 ` Carsten Mattner
2011-12-07 13:52 ` Stefan Monnier
2011-12-07 16:08 ` Dmitry Antipov
2011-12-07 16:30 ` Stefan Monnier
2011-12-08 8:50 ` Dmitry Antipov
2011-12-08 13:52 ` Stefan Monnier
2011-12-08 1:53 ` Stephen J. Turnbull
2011-12-08 4:41 ` Dmitry Antipov
2011-12-08 14:10 ` Stefan Monnier
2011-12-08 16:48 ` Dmitry Antipov
2011-12-08 19:58 ` Stefan Monnier
2011-12-09 7:32 ` Eli Zaretskii
2011-12-09 9:04 ` Dmitry Antipov
2011-12-09 14:05 ` Stefan Monnier
2011-12-09 16:15 ` Dmitry Antipov
2011-12-09 21:04 ` Stefan Monnier
2011-12-11 13:18 ` Dmitry Antipov
2011-12-12 3:07 ` Dmitry Antipov
2011-12-12 16:24 ` Stefan Monnier
2011-12-09 4:44 ` Stephen J. Turnbull
[not found] ` <jwvaa1yjs21.fsf-monnier+emacs@gnu.org>
2012-05-17 7:58 ` Dmitry Antipov
2012-05-18 17:40 ` Stefan Monnier
2012-05-21 12:19 ` Dmitry Antipov
2012-05-21 13:02 ` Andreas Schwab
2012-05-21 13:48 ` Dmitry Antipov
2012-05-21 15:07 ` Andreas Schwab
2012-05-22 5:23 ` Ken Raeburn
2012-05-21 20:12 ` Stefan Monnier
2012-05-22 8:24 ` Dmitry Antipov
2012-05-31 13:44 ` Dmitry Antipov
2012-05-31 15:43 ` Paul Eggert
2012-06-01 5:15 ` Dmitry Antipov [this message]
2012-06-01 5:44 ` Paul Eggert
2012-06-01 9:06 ` Dmitry Antipov
2012-06-01 17:36 ` Stefan Monnier
2012-06-02 0:32 ` Paul Eggert
2012-06-02 7:41 ` Eli Zaretskii
2012-06-03 6:49 ` Paul Eggert
2012-06-03 14:26 ` Eli Zaretskii
2012-05-31 21:16 ` Stefan Monnier
2012-06-01 7:34 ` Dmitry Antipov
2012-06-01 17:40 ` Stefan Monnier
2012-06-01 17:43 ` Stefan Monnier
2012-06-06 7:02 ` Dmitry Antipov
2012-06-06 13:13 ` Stefan Monnier
2012-06-06 14:58 ` Dmitry Antipov
2012-06-06 19:18 ` Stefan Monnier
2012-06-07 10:03 ` Dmitry Antipov
2012-06-07 14:07 ` Stefan Monnier
2012-06-08 5:50 ` Dmitry Antipov
2012-06-08 6:17 ` Stefan Monnier
2012-06-08 8:49 ` Dmitry Antipov
2012-06-08 8:53 ` Eli Zaretskii
2012-06-08 9:41 ` Eli Zaretskii
2012-06-08 10:00 ` Eli Zaretskii
2012-06-08 6:57 ` Eli Zaretskii
2012-06-08 6:38 ` Paul Eggert
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