From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45D0FECAAA1 for ; Tue, 30 Aug 2022 18:57:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229875AbiH3S5x (ORCPT ); Tue, 30 Aug 2022 14:57:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229522AbiH3S5v (ORCPT ); Tue, 30 Aug 2022 14:57:51 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 357BC76472 for ; Tue, 30 Aug 2022 11:57:51 -0700 (PDT) Date: Tue, 30 Aug 2022 20:57:47 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1661885869; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nI0twHoYA12EttbwzHWDC0L+UjAQ6kYDXqqwl07jlCc=; b=Uf4YitVsv5sFBNUK2gzOc/uRllMkYX2/e8NE0vQm14gJ5eh2vT5Qgr4AWrRCJ5Vo840exK HBiMoeW4eoJML0j5p3mFNFwoLj5Twync1QhmWCWoItGDO3HovlKpqO0pVTzzRwK5tgrL1Q uSVYsc/qJyYJoKw58kIupT7XbyF3+9uhgrxpv0cLdZwKia6yAI73dh2dkgb3KeJfvzePmV J8RCeQQwL5ObTH69pDT9ibUl6GToLZmWwXf9xMLTZTZ8cLPKNc3tks6yUmUrV5siZX9rLF PK7qT22bGBXM/T1C+gIXtVLF3KZAV6hgjXCGTH+RGb4fJDsgo1Wj3bpl8qN7zA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1661885869; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nI0twHoYA12EttbwzHWDC0L+UjAQ6kYDXqqwl07jlCc=; b=Ptp/PTS75ojT2z0t6NPxpiFfsHuNfwSfhkn4dvitXWerWH1/AB2YB0stvlQP9T24cQ7h/Z flp1p4baZ6ACzzDw== From: Sebastian Andrzej Siewior To: "Jason A. Donenfeld" Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de Subject: Re: [PATCH] random: use raw spinlocks for use on RT Message-ID: References: <20220801142530.133007-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-08-30 11:24:33 [-0400], Jason A. Donenfeld wrote: > Hi Sebastian, Hi Jason, > On Tue, Aug 30, 2022 at 12:13:44PM +0200, Sebastian Andrzej Siewior wrote: > > The first patch did so yes. The second simply retried in two secs and > > this shouldn't be problematic. >=20 > This seemed pretty bad too, because now you potentially miss up to 2 > seconds of messages AND it adds more complexity. It is early at boot and it could be reduced to one if it helps. I remember you had a suggestion where we would lose always the first print out on RT you said it is okay since you can't rely on that=E2=80=A6 > I'm fine with changing things up to accommodate RT, but not when the > result is so obviously worse than before. I don't think it is worse. This is your opinion and I did not hear any other feedback so far. > In my tests I can't see any latency difference with using raw spinlocks > in random.c. Maybe I'm doing things wrong? But I'm not seeing anything > change... You need to look at the maximum latency that may happen. Also the other thing is that there is no need to add raw_spinlock_t locking if it can be avoided. > Jason Sebastian