From: Jakub Jelinek <jakub@redhat.com>
To: Richard Guenther <rguenther@suse.de>
Cc: Paolo Carlini <paolo.carlini@oracle.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Decrease integer-share-limit
Date: Thu, 16 Aug 2012 14:59:00 -0000 [thread overview]
Message-ID: <20120816145705.GK1999@tucnak.redhat.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1208161643190.28649@zhemvz.fhfr.qr>
On Thu, Aug 16, 2012 at 04:44:03PM +0200, Richard Guenther wrote:
> On Thu, 16 Aug 2012, Paolo Carlini wrote:
> > On 08/16/2012 03:39 PM, Richard Guenther wrote:
> > > This decreases the integer-share-limit to make sure the TREE_VEC we
> > > allocate for the small cached integers has a reasonable size for
> > > our GC memory allocator.
> > Out of curiosity (just in case you hav two spare minutes) do you have any idea
> > why this is so? I mean, naively one would think that allowing for any 8 bit
> > constant would be a nice idea; puzzlingly, however the comment in the code
> > says just "experimentation". I'm wondering if tweaking a bit the memory
> > allocator itself could allow for the full 8 bit range without a big memory
> > waste...
>
> The GC memory allocator works on "pages", there are not pages of
> arbitrary size but only power-of-two sizes. It's hard to improve
> the allocator here.
The allocations are either power-of-two, or a couple of extra listed sizes.
So, the alternative would be to add an extra size for the default integer
share limit vector. See extra_order_size_table in ggc-page.c. Of course
only provided there are many of those vectors.
Jakub
next prev parent reply other threads:[~2012-08-16 14:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-16 13:41 Richard Guenther
2012-08-16 14:37 ` Paolo Carlini
2012-08-16 14:46 ` Richard Guenther
2012-08-16 14:59 ` Jakub Jelinek [this message]
2012-08-17 7:52 ` Richard Guenther
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