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 DC57BC433F5 for ; Fri, 20 May 2022 15:39:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350947AbiETPjw (ORCPT ); Fri, 20 May 2022 11:39:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238804AbiETPjt (ORCPT ); Fri, 20 May 2022 11:39:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3A3A1790AC for ; Fri, 20 May 2022 08:39:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4A745B82C52 for ; Fri, 20 May 2022 15:39:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3399FC34114; Fri, 20 May 2022 15:39:44 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="CdDA93IP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1653061182; 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: in-reply-to:in-reply-to:references:references; bh=RjTQZJZQgulPn2m9ZCd5zit3zBo1nt5rUKPxbyzkWLk=; b=CdDA93IPTM0liA99LP3bUYL8IPFJc4pZ6gUPKjzdV4nx/BEvl9EJnGN38VEwwmD6RTWIfT pV+nKUCZe0863XlzCIqvhI/H+qa8gAxnC4SpUJdlRykLcPBAoSA2EUxAYJG8a477amhden E7A4S+Oxm4haa4x+SR1yqJD/+oTE+7Y= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id fd1a99f0 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Fri, 20 May 2022 15:39:42 +0000 (UTC) Date: Fri, 20 May 2022 17:39:40 +0200 From: "Jason A. Donenfeld" To: Jens Axboe Cc: Theodore Ts'o , Christoph Hellwig , LKML , Al Viro Subject: Re: [PATCH v4 0/3] random: convert to using iters, for Al Viro Message-ID: References: <20220520094459.116240-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jens, On Fri, May 20, 2022 at 09:34:46AM -0600, Jens Axboe wrote: > On 5/20/22 9:25 AM, Jason A. Donenfeld wrote: > > Hi Jens, > > > > On Fri, May 20, 2022 at 11:44:56AM +0200, Jason A. Donenfeld wrote: > >> Jens Axboe (3): > >> random: convert to using fops->read_iter() > >> random: convert to using fops->write_iter() > >> random: wire up fops->splice_{read,write}_iter() > > > > FYI, this series makes reads from /dev/urandom slower, from around 616 > > MiB/s to 598 MiB/s on my system. That seems rather unfortunate. > > How reproducible is that? That seems like a huge difference for the > change. How big are the reads? Fairly reproducible. Actually, if anything, it reproduces consistently with worst results; I chose the most favorable ones for the new code. This isn't any fancy `perf` profiling, but just running: $ pv /dev/urandom > /dev/null >From looking at strace, the read size appears to be 131072. Jason