From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C70C4C73C46 for ; Tue, 9 Jul 2019 19:17:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A0F382082A for ; Tue, 9 Jul 2019 19:17:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726491AbfGITR4 (ORCPT ); Tue, 9 Jul 2019 15:17:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56670 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726133AbfGITR4 (ORCPT ); Tue, 9 Jul 2019 15:17:56 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A952E30821AE; Tue, 9 Jul 2019 19:17:55 +0000 (UTC) Received: from treble (ovpn-112-43.rdu2.redhat.com [10.10.112.43]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9CFD15F9A6; Tue, 9 Jul 2019 19:17:53 +0000 (UTC) Date: Tue, 9 Jul 2019 14:17:51 -0500 From: Josh Poimboeuf To: Alexei Starovoitov Cc: Ingo Molnar , Thomas Gleixner , Steven Rostedt , Kairui Song , Daniel Borkmann , Peter Zijlstra , LKML , bpf Subject: Re: [tip:x86/urgent] bpf: Fix ORC unwinding in non-JIT BPF code Message-ID: <20190709191751.24eq5zx2c7hoqot6@treble> References: <20190707013206.don22x3tfldec4zm@treble> <20190707055209.xqyopsnxfurhrkxw@treble> <20190708223834.zx7u45a4uuu2yyol@treble> <20190708225359.ewk44pvrv6a4oao7@treble> <20190708230201.mol27wzansuy3n2v@treble> <20190709174744.dtbjm72cbu5fepar@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Tue, 09 Jul 2019 19:17:55 +0000 (UTC) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Jul 09, 2019 at 11:02:40AM -0700, Alexei Starovoitov wrote: > On Tue, Jul 9, 2019 at 10:48 AM Josh Poimboeuf wrote: > > > > On Mon, Jul 08, 2019 at 04:16:25PM -0700, Alexei Starovoitov wrote: > > > total time is hard to compare. > > > Could you compare few tests? > > > like two that are called "tcpdump *" > > > > > > I think small regression is ok. > > > Folks that care about performance should be using JIT. > > > > I did each test 20 times and computed the averages: > > > > "tcpdump port 22": > > default: 0.00743175s > > -fno-gcse: 0.00709920s (~4.5% speedup) > > > > "tcpdump complex": > > default: 0.00876715s > > -fno-gcse: 0.00854895s (~2.5% speedup) > > > > So there does seem to be a small performance gain by disabling this > > optimization. > > great. thanks for checking. > > > We could change it for the whole file, by adjusting CFLAGS_core.o in the > > BPF makefile, or we could change it for the function only with something > > like the below patch. > > > > Thoughts? > > > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > > index e8579412ad21..d7ee4c6bad48 100644 > > --- a/include/linux/compiler-gcc.h > > +++ b/include/linux/compiler-gcc.h > > @@ -170,3 +170,5 @@ > > #else > > #define __diag_GCC_8(s) > > #endif > > + > > +#define __no_fgcse __attribute__((optimize("-fno-gcse"))) > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > > index 095d55c3834d..599c27b56c29 100644 > > --- a/include/linux/compiler_types.h > > +++ b/include/linux/compiler_types.h > > @@ -189,6 +189,10 @@ struct ftrace_likely_data { > > #define asm_volatile_goto(x...) asm goto(x) > > #endif > > > > +#ifndef __no_fgcse > > +# define __no_fgcse > > +#endif > > + > > /* Are two types/vars the same type (ignoring qualifiers)? */ > > #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) > > > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > > index 7e98f36a14e2..8191a7db2777 100644 > > --- a/kernel/bpf/core.c > > +++ b/kernel/bpf/core.c > > @@ -1295,7 +1295,7 @@ bool bpf_opcode_in_insntable(u8 code) > > * > > * Decode and execute eBPF instructions. > > */ > > -static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) > > +static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack) > > I prefer per-function flag. > If you want to route it via tip: > Acked-by: Alexei Starovoitov > > or Daniel can take it into bpf tree while I'm traveling. Thanks! I''ll probably send it through the tip tree, along with an objtool fix for the other optimization. -- Josh