From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268574AbUGXNBy (ORCPT ); Sat, 24 Jul 2004 09:01:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268575AbUGXNBy (ORCPT ); Sat, 24 Jul 2004 09:01:54 -0400 Received: from ozlabs.org ([203.10.76.45]:38088 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S268574AbUGXNBv (ORCPT ); Sat, 24 Jul 2004 09:01:51 -0400 Date: Sat, 24 Jul 2004 22:59:37 +1000 From: Anton Blanchard To: torvalds@osdl.org Cc: paulus@samba.org, torvalds@osdl.org, linux-kernel@vger.kernel.org Subject: [PATCH] [ppc64] Exception path optimisations Message-ID: <20040724125937.GH4556@krispykreme> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.6+20040523i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org - We were statically predicting syscalls would be 32bit which meant every 64bit syscall was guaranteed to be mispredicted. Just let the hardware predict this one. - We shouldnt use blrl for indirect function calls, it is unlikely to be predicted correctly and corrupts the link prediction stack. We should use bctrl instead. - Statically predict a branch in the system call path, favouring calls from userspace. - Remove static prediction in pagefault path, hardware prediction should do a better job here. Signed-off-by: Anton Blanchard ===== arch/ppc64/kernel/entry.S 1.41 vs edited ===== --- 1.41/arch/ppc64/kernel/entry.S Thu Jun 17 15:48:02 2004 +++ edited/arch/ppc64/kernel/entry.S Sat Jul 24 22:47:03 2004 @@ -132,7 +132,7 @@ */ ld r11,.SYS_CALL_TABLE@toc(2) andi. r10,r10,_TIF_32BIT - beq- 15f + beq 15f ld r11,.SYS_CALL_TABLE32@toc(2) clrldi r3,r3,32 clrldi r4,r4,32 @@ -143,8 +143,8 @@ 15: slwi r0,r0,3 ldx r10,r11,r0 /* Fetch system call handler [ptr] */ - mtlr r10 - blrl /* Call handler */ + mtctr r10 + bctrl /* Call handler */ syscall_exit: #ifdef SHOW_SYSCALLS @@ -182,7 +182,7 @@ stdcx. r0,0,r1 /* to clear the reservation */ andi. r6,r8,MSR_PR ld r4,_LINK(r1) - beq 1f /* only restore r13 if */ + beq- 1f /* only restore r13 if */ ld r13,GPR13(r1) /* returning to usermode */ 1: ld r2,GPR2(r1) ld r1,GPR1(r1) ===== arch/ppc64/kernel/head.S 1.67 vs edited ===== --- 1.67/arch/ppc64/kernel/head.S Mon Jul 5 20:27:11 2004 +++ edited/arch/ppc64/kernel/head.S Sat Jul 24 22:47:03 2004 @@ -1028,7 +1028,7 @@ bl .local_irq_restore b 11f #else - beq+ fast_exception_return /* Return from exception on success */ + beq fast_exception_return /* Return from exception on success */ /* fall through */ #endif