From patchwork Thu Jan 16 17:58:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 11337503 X-Patchwork-Delegate: paulburton@kernel.org Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 97A9D138D for ; Thu, 16 Jan 2020 17:58:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7575E2469C for ; Thu, 16 Jan 2020 17:58:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="mvz9xrLo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730051AbgAPR6q (ORCPT ); Thu, 16 Jan 2020 12:58:46 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:64763 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394674AbgAPR6i (ORCPT ); Thu, 16 Jan 2020 12:58:38 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 47zBky4VNBz9v4gv; Thu, 16 Jan 2020 18:58:34 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=mvz9xrLo; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 1jI1zVr3Jr4A; Thu, 16 Jan 2020 18:58:34 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 47zBky3SmDz9v4gc; Thu, 16 Jan 2020 18:58:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1579197514; bh=Q6VcAWUVvKepnLf+FFNXtla3CmiLjseY/gtHLv0ppEk=; h=In-Reply-To:References:From:Subject:To:Cc:Date:From; b=mvz9xrLoDf0x9ZlRq7P/56z1YhzUJALo3sg1YXCoFGHBXpwEiqEWD2vNUYaVeXaqM HYDPZtGmygVj1DPIUGjZPFe3z+lhw+HicfayDrRiDhPSzKuwkBeiCfW5vjXVXqm5f/ g1fS2mNXaEY/h0bq58iMBkV7Q/TExNK6gb7mWlbE= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 1E37F8B82D; Thu, 16 Jan 2020 18:58:36 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ioD9o1OpiPdY; Thu, 16 Jan 2020 18:58:36 +0100 (CET) Received: from po14934vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id D80428B82A; Thu, 16 Jan 2020 18:58:35 +0100 (CET) Received: by po14934vm.idsi0.si.c-s.fr (Postfix, from userid 0) id AC38F64A33; Thu, 16 Jan 2020 17:58:35 +0000 (UTC) Message-Id: <29f979e09c84c95f08fcd15386576e32c546d04b.1579196675.git.christophe.leroy@c-s.fr> In-Reply-To: References: From: Christophe Leroy Subject: [RFC PATCH v4 11/11] powerpc/32: provide vdso_shift_ns() To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , nathanl@linux.ibm.com, arnd@arndb.de, tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, x86@kernel.org Date: Thu, 16 Jan 2020 17:58:35 +0000 (UTC) Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org The generic x >> s gives the following result: 18: 35 25 ff e0 addic. r9,r5,-32 1c: 41 80 00 10 blt 2c 20: 7c 64 4c 30 srw r4,r3,r9 24: 38 60 00 00 li r3,0 ... 2c: 54 69 08 3c rlwinm r9,r3,1,0,30 30: 21 45 00 1f subfic r10,r5,31 34: 7c 84 2c 30 srw r4,r4,r5 38: 7d 29 50 30 slw r9,r9,r10 3c: 7c 63 2c 30 srw r3,r3,r5 40: 7d 24 23 78 or r4,r9,r4 In our case the shift is always < 32. In addition, the upper 32 bits of the result are likely nul. Lets GCC know it, it also optimises the following calculations. With the patch, we get: 0: 21 25 00 20 subfic r9,r5,32 4: 7c 69 48 30 slw r9,r3,r9 8: 7c 84 2c 30 srw r4,r4,r5 c: 7d 24 23 78 or r4,r9,r4 10: 7c 63 2c 30 srw r3,r3,r5 Performance before the patch: clock-gettime-realtime: vdso: 1033 nsec/call After the patch: clock-gettime-realtime: vdso: 941 nsec/call Signed-off-by: Christophe Leroy --- arch/powerpc/include/asm/vdso/gettimeofday.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h index 74b6eef8fbe9..716a137ab166 100644 --- a/arch/powerpc/include/asm/vdso/gettimeofday.h +++ b/arch/powerpc/include/asm/vdso/gettimeofday.h @@ -95,6 +95,23 @@ static __always_inline u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 m } #define vdso_calc_delta vdso_calc_delta +#ifndef __powerpc64__ +static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift) +{ + u32 hi = ns >> 32; + u32 lo = ns; + + lo = (lo >> shift) | (hi << (32 - shift)); + hi >>= shift; + + if (likely(hi == 0)) + return lo; + + return ((u64)hi << 32) | lo; +} +#define vdso_shift_ns vdso_shift_ns +#endif + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_VDSO_GETTIMEOFDAY_H */