Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755413AbbDGP2g (ORCPT ); Tue, 7 Apr 2015 11:28:36 -0400 Received: from mail.skyhub.de ([78.46.96.112]:57432 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754104AbbDGP2d (ORCPT ); Tue, 7 Apr 2015 11:28:33 -0400 Date: Tue, 7 Apr 2015 17:26:23 +0200 From: Borislav Petkov To: Denys Vlasenko Cc: Ingo Molnar , Linus Torvalds , Steven Rostedt , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: simplify interrupt dispatch table Message-ID: <20150407152623.GD14095@pd.tnic> References: <1428090553-7283-1-git-send-email-dvlasenk@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1428090553-7283-1-git-send-email-dvlasenk@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2951 Lines: 84 On Fri, Apr 03, 2015 at 09:49:13PM +0200, Denys Vlasenko wrote: > Interrupt entry points are handled with the following code: > Each 32-byte code block contains seven entry points > > ... > [push][jump 22] // 4 bytes > [push][jump 18] // 4 bytes > [push][jump 14] // 4 bytes > [push][jump 10] // 4 bytes > [push][jump 6] // 4 bytes > [push][jump 2] // 4 bytes > [push][jump common_interrupt][padding] // 8 bytes > > [push][jump] > [push][jump] > [push][jump] > [push][jump] > [push][jump] > [push][jump] > [push][jump common_interrupt][padding] > > [padding_2] > common_interrupt: > > And there is a table which holds pointers to every entry point, > IOW: to every push. > > In cold cache, two jumps are still costlier than one, even though we get > the benefit of them residing in the same cacheline. > > This change replaces short jumps with near ones to common_interrupt, and pads > every push+jump pair to 8 bytes. This way, each interrupt takes only one jump. > > This change replaces ".p2align CONFIG_X86_L1_CACHE_SHIFT" before dispatch table > with ".align 8" - we do not need anything stronger than that. > > The table of entry addresses (the interrupt[] array) is no longer > necessary, the address of entries can be easily calculated as > (irq_entries_start + i*8). > > text data bss dec hex filename > 12546 0 0 12546 3102 entry_64.o.before > 11626 0 0 11626 2d6a entry_64.o > > The size decrease is because 1656 bytes of .init.rodata are gone. > That's initdata, though. The resident size does go up a bit. > > Run-tested (32 and 64 bits). > > Signed-off-by: Denys Vlasenko > CC: Linus Torvalds > CC: Steven Rostedt > CC: Ingo Molnar > CC: Borislav Petkov > CC: "H. Peter Anvin" > CC: Andy Lutomirski > CC: Oleg Nesterov > CC: Frederic Weisbecker > CC: Alexei Starovoitov > CC: Will Drewry > CC: Kees Cook > CC: x86@kernel.org > CC: linux-kernel@vger.kernel.org > --- > arch/x86/include/asm/hw_irq.h | 5 ++--- > arch/x86/kernel/entry_32.S | 41 ++++++++++------------------------------- > arch/x86/kernel/entry_64.S | 41 ++++++++++------------------------------- > arch/x86/kernel/irqinit.c | 3 ++- > arch/x86/lguest/boot.c | 3 ++- > 5 files changed, 26 insertions(+), 67 deletions(-) Acked-and-tested-by: Borislav Petkov -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- 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/