From patchwork Mon Mar 20 16:18:55 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 741075 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3vn1Np1yYKz9s3l for ; Tue, 21 Mar 2017 03:19:22 +1100 (AEDT) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="WvBHmHsX"; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753915AbdCTQTD (ORCPT ); Mon, 20 Mar 2017 12:19:03 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:32898 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753669AbdCTQS6 (ORCPT ); Mon, 20 Mar 2017 12:18:58 -0400 Received: by mail-pg0-f65.google.com with SMTP id 79so12037231pgf.0; Mon, 20 Mar 2017 09:18:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=MskR2oFcVs43DjM5gKHHy/wJEdoDs7c83UXe9WIzYBg=; b=WvBHmHsXMNtCqzUCGGnz5IuxLzWUTUyJnE0p/cu06tVt2TldPXUezXWHPoZ2VgZ/Zr EF6ldc91VQRNojdv86aDMfw5yQbnqrHAN7Tc9TIBBFSNhZ6wgfa/IFf4WCLmXNHygRNR 8CrRJECzkeub/68Kj8oBYUKWA6m6cenhm98k0bp4tA29DZQIVmJtBCfMu7rWjM8YWVeF euz1npzVGCLsfpG6cFA1Pzdju+eLyseaPWIGlevNdA4QHFKGukKGxTz9F+lKDU0oiSTw fwduKRFFdUbMYVP5wpTP30zne8gUsmOUGYKQ2VsD4Vmo1TrsIysmp2DZOQZXOU6V/DhJ 8Mgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=MskR2oFcVs43DjM5gKHHy/wJEdoDs7c83UXe9WIzYBg=; b=FvqS81ECrHANVeQReZwZULT0d7MlQLPuXxVcY7YM8I5hc4z5qxokbL8SBS92yAogr/ q/zAvhOI99wRQRliZWkiIUvdgWIlYks0RV7g9aaj/RgOUGFzI6K5B+xbYwFaNrFw8Bto tl6P38WYMTLa4FO8e2p5OWlWsBUk3OcNRFf0s1zICdSUYPz45ha5x0zgxRM83e6J4w+d EQIw0cenhDn1j+A06ITv12bNpOEuyQFpNvGvZWJOzPbPsy4nG01t3j/h8w74OBeM7cB9 oFitOqdQ8cNwoaVV28wOqXPEq5NdQH302b2eSGjbp8mceGotsEcha3pp8bhdrWRdjGcM ftOg== X-Gm-Message-State: AFeK/H1DnraXr1gsjUvmhuC0gKfw9zFhb9xBVjHA8V++E0pvNAHWT9L84xYJ8bdo+wzY1g== X-Received: by 10.84.231.196 with SMTP id g4mr14677798pln.173.1490026737410; Mon, 20 Mar 2017 09:18:57 -0700 (PDT) Received: from ?IPv6:2620:0:1000:1704:996f:f372:800f:e4c? ([2620:0:1000:1704:996f:f372:800f:e4c]) by smtp.googlemail.com with ESMTPSA id h25sm34217275pfk.119.2017.03.20.09.18.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Mar 2017 09:18:56 -0700 (PDT) Message-ID: <1490026735.16816.58.camel@edumazet-glaptop3.roam.corp.google.com> Subject: Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t From: Eric Dumazet To: Peter Zijlstra Cc: Herbert Xu , David Miller , elena.reshetova@intel.com, keescook@chromium.org, netdev@vger.kernel.org, bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kuznet@ms2.inr.ac.ru, jmorris@namei.org, kaber@trash.net, stephen@networkplumber.org, ishkamiel@gmail.com, dwindsor@gmail.com, akpm@linux-foundation.org Date: Mon, 20 Mar 2017 09:18:55 -0700 In-Reply-To: <1490021946.16816.54.camel@edumazet-glaptop3.roam.corp.google.com> References: <1489767196.28631.305.camel@edumazet-glaptop3.roam.corp.google.com> <20170318164759.GA23837@gondor.apana.org.au> <20170318.182121.439615057765380575.davem@davemloft.net> <20170320103937.lq7nfnutupr3gkn7@hirez.programming.kicks-ass.net> <20170320131629.GA26405@gondor.apana.org.au> <20170320132357.acygo3umw6fiwb4p@hirez.programming.kicks-ass.net> <20170320132713.GA26954@gondor.apana.org.au> <20170320134017.h3c2jrsnd4guuyu7@hirez.programming.kicks-ass.net> <1490021461.16816.52.camel@edumazet-glaptop3.roam.corp.google.com> <1490021946.16816.54.camel@edumazet-glaptop3.roam.corp.google.com> X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 2017-03-20 at 07:59 -0700, Eric Dumazet wrote: > On Mon, 2017-03-20 at 07:51 -0700, Eric Dumazet wrote: > > > atomic_cmpxchg() on PowerPC is horribly more expensive because of the > > added two SYNC instructions. > > Although I just saw that refcount was using atomic_cmpxchg_relaxed() > > Time to find some documentation (probably missing) or get some specs for > this thing. Interesting. UDP ipv4 xmit path gets a ~25 % improvement on PPC with this patch. ( 20 concurrent netperf -t UDP_STREAM : 2.45 Mpps -> 3.07 Mpps ) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 8471dd116771462d149e1da2807e446b69b74bcc..9f14aebf0ae1f5f366cfff0fbf58c48603916bc7 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -497,14 +497,14 @@ u32 ip_idents_reserve(u32 hash, int segs) u32 now = (u32)jiffies; u32 new, delta = 0; - if (old != now && cmpxchg(p_tstamp, old, now) == old) + if (old != now && cmpxchg_relaxed(p_tstamp, old, now) == old) delta = prandom_u32_max(now - old); /* Do not use atomic_add_return() as it makes UBSAN unhappy */ do { old = (u32)atomic_read(p_id); new = old + delta + segs; - } while (atomic_cmpxchg(p_id, old, new) != old); + } while (atomic_cmpxchg_relaxed(p_id, old, new) != old); return new - segs; }