From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1534C1BBBC5 for ; Wed, 20 Nov 2024 20:37:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732135044; cv=none; b=oTMp70fBb4v6txsH6X2y6y/gwKXYuRdFjtIBs5o/9i6xLDFv0DsJhwyZzaa3deXP3H0kWYsocesj37XZY0L92GjnhgIwn2pX4xARU96I2xhJ8dxInJwH2ugXVQLv0t7LcMfNfD312buNZHOcb4H1IBM2uNMiKj7J1ojCBnVjldk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732135044; c=relaxed/simple; bh=gxdo/qfNxQeE8KQho8RvlhXWrZvSkpA6qPXBeVgUJXo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZaqUE9AldUuEt+TiZsbiBS9Qil/pHmaCwR9ypjo+V0x+qhH2pgnonKbZ2397bOga8qAPFkIkuXW/sksckCv1Xn1C/X+pJoLFQjXFTSSztiJY4LWIN6VlXYVQcgvFQcKrjyoaj4KhrncyfDSrZWwoa40fPBudg5CfycJ8QKR/NrQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fromorbit.com; spf=pass smtp.mailfrom=fromorbit.com; dkim=pass (2048-bit key) header.d=fromorbit-com.20230601.gappssmtp.com header.i=@fromorbit-com.20230601.gappssmtp.com header.b=Q++p/NM5; arc=none smtp.client-ip=209.85.210.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fromorbit.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fromorbit.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fromorbit-com.20230601.gappssmtp.com header.i=@fromorbit-com.20230601.gappssmtp.com header.b="Q++p/NM5" Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-720d01caa66so204823b3a.2 for ; Wed, 20 Nov 2024 12:37:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fromorbit-com.20230601.gappssmtp.com; s=20230601; t=1732135041; x=1732739841; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=j7agw+MVRyIWuBCl7pZ+mHszf9nzIBAC/CJ3AinkBqw=; b=Q++p/NM5V2P0QCp2VjUddqV8grc4gu6TasiyBOjEJQMiSQgildyUd8BLF97mO16/gX kTe1Jos6tv+4nNZPMMMSPx6HSzOetxJw82emuaY6c0d3ITXa3luQTBYGSay+ie+6oABL TOJ1SCQiHGe1R75MPDrXtVZ/QlTWHU4jrPsRzdipsip9KcV5nAA1aio0kXTzHCSKLlTG k/i6fvt7Cd8OkTorLtfhQWGGVV52tDjb0ASwIvHHLTOh3eLBffLLJR5/4WKbuR6q99Rb vGfkeqp9eFbmc3ow7QN9qYTkKYrhRlJinKXsmg2NJHCKu+puEBR4zawIeTf45GOEcxHO JrsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732135041; x=1732739841; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=j7agw+MVRyIWuBCl7pZ+mHszf9nzIBAC/CJ3AinkBqw=; b=lQRRU/aK7HNP1mrHZX/4d03/9SB/POOuRmfT4/iWWXa2AJKSvLEAqzEr6YMZnsK/Uz e/ZJFgzLxxs90lLMJrzanB6WeBikR1Lbo0Y1yN82i9wy+mEPo/T/p4RWcEVxI1ndc1XW tfADQepaTtBDp9zGq0KOrA0PqJGNCKWBEbTnPYdx/qpQ+glPegtrRbjLQIH22EErxQ2I au2psylF+Jd1Hstswpj1QKMho/c5vXuCrK11iavBZBIlZdR4hcySb74V9jpOtlX4AXdu s6Mu5JbOiexbJTBasoiX83wV2YB/cfLHyCxHzDFE77g8ksw5IC1dG1JnR8C8zPiUA3X0 en0g== X-Forwarded-Encrypted: i=1; AJvYcCWrP/1fw1b1qQd8uzPkTgZQu6IKBoV9C3iAY/q9SBY3f5P9NxkpAJqQ7DsuObHc8gQI2NMgGI4k4NNQeqY=@vger.kernel.org X-Gm-Message-State: AOJu0Yxz6ueOuFkHVRRhj3TqFcIhSlLjbZyNQZADJb231Srt2O/E+CJz GgJjMCyDcV+dJJo1+ZpDR3B1uGilbMKlxAr+7XPTsGeUcsXnp2OkNhbLhs2Udoo= X-Google-Smtp-Source: AGHT+IGreu4pbRdf9RAsxW9otLcD4fFTHm8D1pwAWAPrW4pJkHesAy9VcpvXrA5aTGE2ELi+7vWGbw== X-Received: by 2002:a17:90b:52c3:b0:2ea:b564:4b35 with SMTP id 98e67ed59e1d1-2eaca6e41f2mr5271046a91.9.1732135041400; Wed, 20 Nov 2024 12:37:21 -0800 (PST) Received: from dread.disaster.area (pa49-180-121-96.pa.nsw.optusnet.com.au. [49.180.121.96]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ead03de6f6sm1762377a91.34.2024.11.20.12.37.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2024 12:37:20 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.98) (envelope-from ) id 1tDrRt-000000010Wl-2glT; Thu, 21 Nov 2024 07:37:17 +1100 Date: Thu, 21 Nov 2024 07:37:17 +1100 From: Dave Chinner To: Uros Bizjak Cc: linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, Chandan Babu R , "Darrick J. Wong" , Christoph Hellwig , Dave Chinner Subject: Re: [PATCH] xfs: Use xchg() in xlog_cil_insert_pcp_aggregate() Message-ID: References: <20241120150725.3378-1-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241120150725.3378-1-ubizjak@gmail.com> On Wed, Nov 20, 2024 at 04:06:22PM +0100, Uros Bizjak wrote: > try_cmpxchg() loop with constant "new" value can be substituted > with just xchg() to atomically get and clear the location. > > The code on x86_64 improves from: > > 1e7f: 48 89 4c 24 10 mov %rcx,0x10(%rsp) > 1e84: 48 03 14 c5 00 00 00 add 0x0(,%rax,8),%rdx > 1e8b: 00 > 1e88: R_X86_64_32S __per_cpu_offset > 1e8c: 8b 02 mov (%rdx),%eax > 1e8e: 41 89 c5 mov %eax,%r13d > 1e91: 31 c9 xor %ecx,%ecx > 1e93: f0 0f b1 0a lock cmpxchg %ecx,(%rdx) > 1e97: 75 f5 jne 1e8e > 1e99: 48 8b 4c 24 10 mov 0x10(%rsp),%rcx > 1e9e: 45 01 e9 add %r13d,%r9d > > to just: > > 1e7f: 48 03 14 cd 00 00 00 add 0x0(,%rcx,8),%rdx > 1e86: 00 > 1e83: R_X86_64_32S __per_cpu_offset > 1e87: 31 c9 xor %ecx,%ecx > 1e89: 87 0a xchg %ecx,(%rdx) > 1e8b: 41 01 cb add %ecx,%r11d > > No functional change intended. > > Signed-off-by: Uros Bizjak > Cc: Chandan Babu R > Cc: "Darrick J. Wong" > Cc: Christoph Hellwig > Cc: Dave Chinner > --- > fs/xfs/xfs_log_cil.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c > index 80da0cf87d7a..9d667be1d909 100644 > --- a/fs/xfs/xfs_log_cil.c > +++ b/fs/xfs/xfs_log_cil.c > @@ -171,11 +171,8 @@ xlog_cil_insert_pcp_aggregate( > */ > for_each_cpu(cpu, &ctx->cil_pcpmask) { > struct xlog_cil_pcp *cilpcp = per_cpu_ptr(cil->xc_pcp, cpu); > - int old = READ_ONCE(cilpcp->space_used); > > - while (!try_cmpxchg(&cilpcp->space_used, &old, 0)) > - ; > - count += old; > + count += xchg(&cilpcp->space_used, 0); > } > atomic_add(count, &ctx->space_used); > } Looks fine. Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com