From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f48.google.com (mail-ed1-f48.google.com [209.85.208.48]) (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 8934D481245 for ; Mon, 18 May 2026 13:59:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779112800; cv=none; b=EOlLVh0O7ASp0xSYT2QJjyhNglhj0Pqe6hGt/oCwYfJ35Zp+/gG4SFFK6Jr+bwOClU2MGNeby0ZvQZhXZ997rU7Az+boF9q6F87Geua8DY5ckRnjQCNLrUnX9grUq3p1qgFqWshTD7jx6ht9labBSMmY5WBp3zZrGu+e6jbQd6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779112800; c=relaxed/simple; bh=MXTgLfPj/f1h325rq7FWLxCdh3CeoPcDyvJ5aI3aWzQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=n/BoOFEXdBnv7qVQ+iczN2UgYLihbzdPSIqpQ1WlJaQdRTLm5ntYsRg0FnkdFHqy6tMHeCmbRE+B48GQxonVzwbrC7ttkb6o//r6n3DcoNAVbfbTswzo4V/fCMBYZJINhbbEOgIzZzvvSNWPW6sFGv47YhX8rjZpcxxepJZ6OKM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=OOOc+c5J; arc=none smtp.client-ip=209.85.208.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="OOOc+c5J" Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-67b32c695efso7118970a12.1 for ; Mon, 18 May 2026 06:59:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779112797; x=1779717597; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=+WT00WHtAu4WqCgP+skKdKZ8K4Rq+JbbmW7SvyUtdIs=; b=OOOc+c5JDZpSmhka23oYEOg+ROkjXJVULMzl2HVHv64Ntjq7Dh8Yd7RWeENxZo9ps5 KZUQpoIuFMqYgZJmDwjQxwB9VWa7YEtiEWSD1JL3PWwpiwM+iGAcC9vmq8YL+1ZFZcnk Pw7BriH8opyUYq0yCxYVdVr4gRcncSEPsnVSvWEQTvF3Gm3bMk1b44T8BMKI9eX9k7Wh kk2zXj+9okLSUDZ1fQx0DR9R826qiAdQVWZvZbkPFV6XY3r/jAiok7Jt+DEyvjUZCL3C JI8b1ADQtCWzvtZQ+TMmSzNjjvGM5O4y9DKH7WJ0ngBwdJT37RxaXUC/saca5NI91v7m 2kkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779112797; x=1779717597; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=+WT00WHtAu4WqCgP+skKdKZ8K4Rq+JbbmW7SvyUtdIs=; b=N2/1XXgWUXm7VQMTd/DqhAQ4TrwldsPSwNB4f/fF55tQy3QWqTee46IwqgxBU8T72Q rp1fiRkm6DehwTiIrFqpj2Qs2XABwRgkUR993vmxcJQBpwVQxO2pY/sMJAXeOlWpoY2w VhxaIBv0fuCMUAgHnaHTqX6aKaI8h9Lo/yowlh2py+3Wd2rSciHhHx4+VtpXmUREDoVX 1O4LAQ0QBX9A/gbaxfYU6iaWvEmtzUbpGLgds6BzoU2vKFvYBZMabmzsas9uLXAwWgBl rQn1W5SkoTxM/0IMDHKcBZ6D351kgmaVTh/QeMKMjB/IqT5KukMkkHH+mkJ84bQ9ASGr 5d3w== X-Forwarded-Encrypted: i=1; AFNElJ+QppdyxO0K4k54JEfKD83wxRWMpvqWuyhVXQCC5luWdPgBoneWaCdl8qic0GKNLzAPwu5mT6mR9ndytQ==@vger.kernel.org X-Gm-Message-State: AOJu0Yy0TuPxcCgZzXP7GUMagNAdTT4TqS5jbSq9m9hAMF6i0vad4R0E vvOyJ0P81cpzRv5/8N2cWbOR/XELNxXPjG66yKTOeGN7mAVNhQqe7I6J X-Gm-Gg: Acq92OHGtizVOJoceF2/FnEbMvqTlIAkJZBKr/wP8bob4Ht76KnrDtBr4HFngMma+Zf 6QIzt/UWe0t4VrMzKyjJFgVlLQlvVs/Se/y5gGJj/KZ6sf95ZX3q3HNpRHF/ySh7n7k9J6/dZV8 vjZ/q2pCSdaY0YaZTZGUbS3rnzYfC1MC2psVH9/0yYtWUhgVhXaP7f9U3sh0LS3cmLB80hzMBby ZgrE89myEqIxhkJRQde6g57DNPaWXu6EzswSsp1Xiu/Ck+0Bs8c4LyF/H45uxyu93mzmoemmo+X SvKyNxJ21LQpctfHtXRGLkZzpsrIfv3EObebcEuvCUf5PiTAiTkmwBmFgCG7JAO6LgxiArxgX0E xuLayv/6/7aVn97RRfoTzxSOk/XARV9fApK5DcjylYMDVJVMi+yCpteJp71fYxknjIxQOJg6QNX uGmHCm5/yaFo1yIU/OEMlNl/DJihDwCXeKQrCzjDHHowW7i0k8CWbqjH78txQSB9wC4u5Yv151/ gqgdnJhT3O3GspnZQN8LiBLV9H0GGUtMXQ0ZQM4TjV7EGs3JJcgZoBxW23u7LrnhPldg8Z0S6Ua SViKvLaSaerL X-Received: by 2002:a17:907:3f1d:b0:bc1:7da0:21 with SMTP id a640c23a62f3a-bd4f34bd0e3mr858876966b.23.1779112796524; Mon, 18 May 2026 06:59:56 -0700 (PDT) Received: from ?IPV6:2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c? ([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-bd4f4dea94bsm565057266b.33.2026.05.18.06.59.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 May 2026 06:59:55 -0700 (PDT) Message-ID: <166da921-77bd-422e-85af-ef67d6fccc42@gmail.com> Date: Mon, 18 May 2026 14:59:54 +0100 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 04/10] block: introduce dma map backed bio type To: Christoph Hellwig Cc: =?UTF-8?Q?Christian_K=C3=B6nig?= , Jens Axboe , Keith Busch , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Phil Cayton , Jason Gunthorpe References: <646ecd6fde8d9e146cb051efb514deb27ce3883e.1777475843.git.asml.silence@gmail.com> <20260513081929.GD5477@lst.de> <24833f76-2289-4859-86d1-9215b11a1258@gmail.com> <4561c621-817c-46be-8ff0-0b557f6c819d@gmail.com> <20260518125713.GC5754@lst.de> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20260518125713.GC5754@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/18/26 13:57, Christoph Hellwig wrote: > On Mon, May 18, 2026 at 01:40:18PM +0100, Pavel Begunkov wrote: >>> When that is really a performance critical path then you can use the likely() and unlikely() macros to give the compiler the hint which one to prefer. >> >> That might be more penalising than placing them in the right order, >> and it might be fine as it's new and all that, but it's not a clear >> cut as it's definitely not created to be a slow path. > > Yes. Whatever the caller is using at a given time is the fast path here, > and dynamic branch prediction in modern cpus handles this really well. > >> TBH, not sure >> why we're bike shedding such things, is it somewhere in the code >> style? > > It makes reading the code annoying, so it better have a good reason. > Now for a single conditional it's not much of an issue, but these > things tend to pile up and then start to get really annoying. > Always write your code the most straight forward way unless you > have a good reason not to. For me, having the most common case first is more natural and readable, but I'm going to flip it just to avoid spending more time here. -- Pavel Begunkov