From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [66.187.233.31]) by ozlabs.org (Postfix) with ESMTP id 5B6E9679F3 for ; Wed, 10 May 2006 20:16:33 +1000 (EST) From: David Howells In-Reply-To: <1147245709.32448.74.camel@localhost.localdomain> References: <1147245709.32448.74.camel@localhost.localdomain> <17505.26159.807484.477212@cargo.ozlabs.ibm.com> <20060510051649.GD1794@lixom.net> <17505.34919.750295.170941@cargo.ozlabs.ibm.com> <20060509.233958.73723993.davem@davemloft.net> To: Benjamin Herrenschmidt Subject: Re: [RFC/PATCH] Make powerpc64 use __thread for per-cpu variables Date: Wed, 10 May 2006 11:14:53 +0100 Message-ID: <14201.1147256093@warthog.cambridge.redhat.com> Sender: dhowells@redhat.com Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, paulus@samba.org, olof@lixom.net, "David S. Miller" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Benjamin Herrenschmidt wrote: > > That first cache line of current_thread_info() should be so hot that > > it's probably just fine to use current_thread_info()->task since > > you're just doing a mask on a fixed register (r1) to implement that. > > Iirc, he tried that, though it did bloat the kernel size a bit due the > the amount of occurences of current-> in there. We are now thinking > about either dedicating a register to current (that would avoid the > problem of printk() using it in start_kernel before we get the per-cpu > areas setup) in addition to __thread (heh, we have lots of registers on > ppc :) or maybe putting current back in the paca... I dedicated registers to current and current threadinfo in the FRV arch. As I recall doing that improved both performance and code size quite a bit. It also means that I get sensible bug panic reports when the stack pointer overruns the stack space. David