From owner-freebsd-arch@freebsd.org Sat Nov 14 11:22:50 2020 Return-Path: Delivered-To: freebsd-arch@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 454B82E6F55 for ; Sat, 14 Nov 2020 11:22:50 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (turbocat.net [88.99.82.50]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4CYCcT3jf5z4pSZ; Sat, 14 Nov 2020 11:22:49 +0000 (UTC) (envelope-from hps@selasky.org) Received: from hps2020.home.selasky.org (unknown [178.17.145.105]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id AF5AA260459; Sat, 14 Nov 2020 12:22:41 +0100 (CET) Subject: Re: MAXPHYS bump for FreeBSD 13 To: Alexander Motin , "freebsd-arch@freebsd.org" References: <1bff381f-3d6e-b20c-28f9-1403a9dfe0f6@FreeBSD.org> From: Hans Petter Selasky Message-ID: <07a4ca53-da9d-e7b2-9af3-c5098f15a5c7@selasky.org> Date: Sat, 14 Nov 2020 12:22:36 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:78.0) Gecko/20100101 Thunderbird/78.4.1 MIME-Version: 1.0 In-Reply-To: <1bff381f-3d6e-b20c-28f9-1403a9dfe0f6@FreeBSD.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4CYCcT3jf5z4pSZ X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of hps@selasky.org designates 88.99.82.50 as permitted sender) smtp.mailfrom=hps@selasky.org X-Spamd-Result: default: False [-3.30 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; MIME_GOOD(-0.10)[text/plain]; R_SPF_ALLOW(-0.20)[+a:mail.turbocat.net]; RBL_DBL_DONT_QUERY_IPS(0.00)[88.99.82.50:from]; DMARC_NA(0.00)[selasky.org]; SPAMHAUS_ZRD(0.00)[88.99.82.50:from:127.0.2.255]; ARC_NA(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_HAM_SHORT(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:88.99.0.0/16, country:DE]; RCVD_COUNT_TWO(0.00)[2]; MAILMAN_DEST(0.00)[freebsd-arch] X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Nov 2020 11:22:50 -0000 On 11/14/20 5:14 AM, Alexander Motin wrote: >> We currently have a MAXPHYS of 128k. This is the maximum size of I/Os >> that we normally use (though there are exceptions). >> >> I'd like to propose that we bump MAXPHYS to 1MB, as well as bumping >> DFLTPHYS to 1MB. > > I am all for the MAXPHYS change, as Warner told it was my proposition on > a chat. ZFS uses blocks and aggregates I/O up to 1MB already and can > more potentially, and having I/O size lower then this just overflows > disk queues, increases processing overheads, complicates scheduling and > in some cases causes starvation. > > I'd just like to note that DFLTPHYS should probably not be changed that > straight (if at all), since it is used as a fallback for legacy code. > If it is used for anything else -- that should be reviewed and probably > migrated to some other constant(s). > Beware that many USB 2.0 devices will break if you try to transfer more than 64K. Buggy SCSI implementations! --HPS