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From: Fabrice Bellard <fabrice@bellard.org>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] env in TLS
Date: Mon, 11 Oct 2004 11:41:37 +0200	[thread overview]
Message-ID: <416A5551.9080703@bellard.org> (raw)
In-Reply-To: <20041011083228.6907.qmail@web52501.mail.yahoo.com>

Using TLS seems a good idea. I hesitated to implement it because I was 
not sure that segment overrides were as fast as an indexed memory access 
on all x86 processors. I think that imposing a gcc version >= 3.2 is no 
longer an issue. We must be sure that the other platforms support the 
__thread keyword though.

Fabrice.

Piotr Krysik wrote:
> Hi!
> 
> Fabrice, how about moving env variable to TLS?
> 
> This could improve performance (based on 
> http://lists.gnu.org/archive/html/qemu-devel/2004-09/msg00294.html
> 
> about 10% could be gained -- need to verify). Also 
> additional register would be available for op.c 
> (anyone to implement register renaming?).
> 
> The main problem with this approach is portability. 
> AFAIK GCC <= 3.2 doesn't recognize __thread keyword. 
> For x86 we could fall-back to the LDT method from 
> qemu-fast. How about other platforms? In the worst 
> case we could use global variable and forget about 
> multi-processor qemu-softmmu and multi-thread in 
> qemu-user for some platforms in the future.
> 
> 
> Comments?
> 
> Piotrek
> 
> 
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  reply	other threads:[~2004-10-11  9:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-10-11  8:32 [Qemu-devel] env in TLS Piotr Krysik
2004-10-11  9:41 ` Fabrice Bellard [this message]
2004-10-11 10:33   ` Lennert Buytenhek
2004-10-11 12:18     ` Johannes Schindelin
2004-10-11 12:37       ` Lennert Buytenhek
2004-10-11 14:59         ` Johannes Schindelin
2004-10-11 17:30           ` Lennert Buytenhek
2004-10-11 22:01             ` Johannes Schindelin
2004-10-12  2:33   ` André Braga
2004-10-11 21:34 ` Rafael Espíndola

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