Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754366AbbGTKz0 (ORCPT ); Mon, 20 Jul 2015 06:55:26 -0400 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:59765 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753512AbbGTKzZ (ORCPT ); Mon, 20 Jul 2015 06:55:25 -0400 X-Helo: d23dlp02.au.ibm.com X-MailFrom: ananth@in.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Subject: [PATCH V3 2/2] kprobes: Mark OPTPROBES na for powerpc From: Ananth N Mavinakayanahalli To: masami.hiramatsu.pt@hitachi.com, mpe@ellerman.id.au, mingo@kernel.org Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Mon, 20 Jul 2015 16:24:22 +0530 Message-ID: <20150720105417.24801.66440.stgit@thinktux.in.ibm.com> In-Reply-To: <20150720105349.24801.64387.stgit@thinktux.in.ibm.com> References: <20150720105349.24801.64387.stgit@thinktux.in.ibm.com> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15072010-0005-0000-0000-0000022433F6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1712 Lines: 40 Kprobes uses a breakpoint instruction to trap into execution flow and the probed instruction is single-stepped from an alternate location. On some architectures like x86, under certain conditions, the OPTPROBES feature enables replacing the probed instruction with a jump instead, resulting in a significant perfomance boost (both the breakpoint and single-step exception is bypassed for each kprobe). Powerpc has an in-kernel instruction emulator. Kprobes on powerpc uses this emulator already and bypasses the single-step exception, with a lot less complexity. There is a potential gain to be had with a direct jump instead of a breakpoint, but the caveats need to be traded off with the complexity it brings in. For now, mark OPTPROBES na for powerpc. Signed-off-by: Ananth N Mavinakayanahalli --- .../features/debug/optprobes/arch-support.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/features/debug/optprobes/arch-support.txt b/Documentation/features/debug/optprobes/arch-support.txt index b8999d8..73662f9 100644 --- a/Documentation/features/debug/optprobes/arch-support.txt +++ b/Documentation/features/debug/optprobes/arch-support.txt @@ -27,7 +27,7 @@ | nios2: | TODO | | openrisc: | TODO | | parisc: | TODO | - | powerpc: | TODO | + | powerpc: | na | | s390: | TODO | | score: | TODO | | sh: | TODO | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/