From: Ralf Baechle <ralf@linux-mips.org>
To: Thiemo Seufer <ths@networkno.de>
Cc: Carl van Schaik <carl@ok-labs.com>, linux-mips@linux-mips.org
Subject: Re: TLS register for NPTL
Date: Mon, 20 Aug 2007 15:54:49 +0100 [thread overview]
Message-ID: <20070820145449.GA11766@linux-mips.org> (raw)
In-Reply-To: <20070820080627.GF4479@networkno.de>
On Mon, Aug 20, 2007 at 09:06:27AM +0100, Thiemo Seufer wrote:
> > It seems the rdhwr emulation is used/proposed for accessing the thread
> > word in NPTL.
> > I've been reading some of the posts from 2005 about this choice of this
> > and what I have missed is anyone talking about using the "k0" register
> > for TLS. It seems logical that the kernel could always restore k0 on
> > returning to user-land and having k1 only for the last part of returning
> > to user is sufficient. Any reason why this was not looked at?
>
> The TLB handlers need k0/k1 as well and have no good place to save/restore
> a register.
It can be done but would require several extra instructions in the most
performance sensitive parts of the OS.
Aside, latest MIPS processors support a hardware implementation of rdhwr $29,
so there is no more emulation overhead for this instruction at full binary
compatibility.
Ralf
next prev parent reply other threads:[~2007-08-20 14:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-20 6:59 TLS register for NPTL Carl van Schaik
2007-08-20 8:06 ` Thiemo Seufer
2007-08-20 14:54 ` Ralf Baechle [this message]
2007-08-21 1:53 ` Carl van Schaik
2007-08-21 12:42 ` Ralf Baechle
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