From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE575201266; Sat, 22 Feb 2025 23:51:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740268285; cv=none; b=SjJqJ/1hEL7Rtx1dGNAMeXPQOsx3f7hVQi8njOz1kKlogd+g2024GZE0Zl/uGPH9OhbsBC/sQohPr6adsdAIex3LugFF4bwMWZCvc02ooxpZB+vfLZ3Zkyq/pmfjg6FspMdHLt2fb+Mt+uFEiMoJLRyd580iJ7CH0Gniv6Pz7mQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740268285; c=relaxed/simple; bh=BUzYO5WNI0AvIV65QgeIcllxZT6M0OQeWB3k+6nghto=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=fX8WTkWbjj6RkCczkM7HVnK0S3XTZKRiZY6YbNB7Psa4g4V0PZJbPMo32PX9JF3F5g4a2Cynrv8UhDEBFnX1tAvf21y5Nf2awi+SGN0Q6Oc83wIPgcCuktohcSJlnRA4UDwYAULZarkirsEwfYQEKAF8pqBAKhjZf/sOeu0xNgo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=wy2Qk700; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="wy2Qk700" Received: from [IPv6:::1] ([172.59.160.4]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 51MNp5Sj3857546 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sat, 22 Feb 2025 15:51:06 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 51MNp5Sj3857546 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025021701; t=1740268267; bh=/+nn2rQ/7gqR+dEBO1aJufprBuwk9A8ZUqZnTRwjCes=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=wy2Qk700Kt5HER5PMi4N6WC6wigTrEclUj6Nbe/+p2kEBxRpdA9PzEfuoO2XBf2/a iWg71U7XW921i92gYXs5Q2Yye/96v9I5si/RIblHu8XZGlFCxNmxA4tfj5YJBY0IPy yihby4SfJVBzKKQMXw7q9QaA/2+8M+CtEW3gnsLL4sNWuBRb+Bau3vDuxStnRv0UOS QLCxOj1gOmxfo29UmbYTjS3EzFYIFxzPI3RPlo/bq+G5bFVNC9YHZRWRcdEyYalDvE 4fdNxGawsFNiWAW4pJKv4UIBoZIJUctcq3Pl6ZwndPS98KAj+AHyPbrVCpP9e95vH3 9G4PDYBYiCYXw== Date: Sat, 22 Feb 2025 15:50:59 -0800 From: "H. Peter Anvin" To: Kent Overstreet CC: Linus Torvalds , Ventura Jack , Gary Guo , airlied@gmail.com, boqun.feng@gmail.com, david.laight.linux@gmail.com, ej@inai.de, gregkh@linuxfoundation.org, hch@infradead.org, ksummit@lists.linux.dev, linux-kernel@vger.kernel.org, miguel.ojeda.sandonis@gmail.com, rust-for-linux@vger.kernel.org Subject: Re: C aggregate passing (Rust kernel policy) User-Agent: K-9 Mail for Android In-Reply-To: References: <20250222141521.1fe24871@eugeo> <6pwjvkejyw2wjxobu6ffeyolkk2fppuuvyrzqpigchqzhclnhm@v5zhfpmirk2c> <6EFFB41B-9145-496E-8217-07AF404BE695@zytor.com> Message-ID: Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On February 22, 2025 1:22:08 PM PST, Kent Overstreet wrote: >On Sat, Feb 22, 2025 at 12:54:31PM -0800, H=2E Peter Anvin wrote: >> VLIW and OoO might seem orthogonal, but they aren't =E2=80=93 because t= hey are >> trying to solve the same problem, combining them either means the OoO >> engine can't do a very good job because of false dependencies (if you >> are scheduling molecules) or you have to break them instructions down >> into atoms, at which point it is just a (often quite inefficient) RISC >> encoding=2E In short, VLIW *might* make sense when you are statically >> scheduling a known pipeline, but it is basically a dead end for >> evolution =E2=80=93 so unless you can JIT your code for each new chip >> generation=2E=2E=2E > >JITing for each chip generation would be a part of any serious new VLIW >effort=2E It's plenty doable in the open source world and the gains are >too big to ignore=2E > >> But OoO still is more powerful, because it can do *dynamic* >> scheduling=2E A cache miss doesn't necessarily mean that you have to >> stop the entire machine, for example=2E > >Power hungry and prone to information leaks, though=2E > I think I know a thing or two about JITting for VLIW=2E=2E and so does so= meone else in this thread ;)