From owner-freebsd-bugs@freebsd.org Fri May 18 23:54:53 2018 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id D9506EE0DCD for ; Fri, 18 May 2018 23:54:52 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 5B31D70894 for ; Fri, 18 May 2018 23:54:52 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id 1B561EE0DCA; Fri, 18 May 2018 23:54:52 +0000 (UTC) Delivered-To: bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 09917EE0DC8 for ; Fri, 18 May 2018 23:54:52 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.ysv.freebsd.org (mxrelay.ysv.freebsd.org [IPv6:2001:1900:2254:206a::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.ysv.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 9542070893 for ; Fri, 18 May 2018 23:54:51 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.ysv.freebsd.org (Postfix) with ESMTPS id B6CD823DCB for ; Fri, 18 May 2018 23:54:50 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id w4INsoSJ079419 for ; Fri, 18 May 2018 23:54:50 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id w4INsomU079418 for bugs@FreeBSD.org; Fri, 18 May 2018 23:54:50 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 228335] [patch] virtio indirect descriptors should use contiguous memory Date: Fri, 18 May 2018 23:54:50 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.1-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: bryanv@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 May 2018 23:54:53 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D228335 --- Comment #1 from Bryan Venteicher --- See this comment in virtio.h: /* * Each virtqueue indirect descriptor list must be physically contiguous. * To allow us to malloc(9) each list individually, limit the number * supported to what will fit in one page. With 4KB pages, this is a limit * of 256 descriptors. If there is ever a need for more, we can switch to * contigmalloc(9) for the larger allocations, similar to what * bus_dmamem_alloc(9) does. * * Note the sizeof(struct vring_desc) is 16 bytes. */ #define VIRTIO_MAX_INDIRECT ((int) (PAGE_SIZE / 16)) This code is quite old but my recollection is that the minimum allocation returned by contigmalloc() is (was?) a page which ends up wasting a lot of memory. What is the "different memory allocator"? If you're indifferent to VirtIO then disabling indrect descriptors is an option. However, I believe there are a handful of other places in VirtIO where the malloc allocation is capped at one page. That being said, I don't like depending on the behavior of malloc behavior here. I'm working on VirtIO V1 support, and after that, was going to switch VirtIO to bus_dma(9) for later IOMMU/"physical" virtio devices support. --=20 You are receiving this mail because: You are the assignee for the bug.=