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 X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C3FAC35247 for ; Thu, 6 Feb 2020 20:12:27 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 67CDB2192A for ; Thu, 6 Feb 2020 20:12:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZbBiureW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 67CDB2192A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45416 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iznVi-0008OT-I7 for qemu-devel@archiver.kernel.org; Thu, 06 Feb 2020 15:12:26 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41104) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iznV5-0007wq-Uo for qemu-devel@nongnu.org; Thu, 06 Feb 2020 15:11:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iznV4-0003Jy-4h for qemu-devel@nongnu.org; Thu, 06 Feb 2020 15:11:47 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:21275 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iznV3-0003Gn-W6 for qemu-devel@nongnu.org; Thu, 06 Feb 2020 15:11:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581019905; 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=u9aoD5UNMxOvZIruDj5OKzAJd+8pjB96nm/Rf9NL/hQ=; b=ZbBiureWUfQqoUuVw5YJZgljUx4EQdPCzz7pF1GBBIp83qrt0xL0WkNTR4ENfxqgr739e9 gTglmxaRn2t7Lx8gvGTbtab5ID9JgZa66ttuuTIC/sh0CJnL3+fFY/uHsDc9aBzbowg061 DT1goZwyZgd6x/n9qUZUOfFD/hmQ8JM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-338-5W-tQpTZONqsMFWrD6evbQ-1; Thu, 06 Feb 2020 15:11:37 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E1577DB60; Thu, 6 Feb 2020 20:11:35 +0000 (UTC) Received: from work-vm (unknown [10.36.118.75]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 37741859A5; Thu, 6 Feb 2020 20:11:24 +0000 (UTC) Date: Thu, 6 Feb 2020 20:11:21 +0000 From: "Dr. David Alan Gilbert" To: David Hildenbrand Subject: Re: [PATCH v1 00/13] Ram blocks with resizable anonymous allocations under POSIX Message-ID: <20200206201121.GM3655@work-vm> References: <20200203183125.164879-1-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200203183125.164879-1-david@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: 5W-tQpTZONqsMFWrD6evbQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , "Michael S . Tsirkin" , Markus Armbruster , qemu-devel@nongnu.org, Greg Kurz , Alex Williamson , Murilo Opsfelder Araujo , Paolo Bonzini , Stefan Weil , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * David Hildenbrand (david@redhat.com) wrote: > We already allow resizable ram blocks for anonymous memory, however, they > are not actually resized. All memory is mmaped() R/W, including the memor= y > exceeding the used_length, up to the max_length. >=20 > When resizing, effectively only the boundary is moved. Implement actually > resizable anonymous allocations and make use of them in resizable ram > blocks when possible. Memory exceeding the used_length will be > inaccessible. Especially ram block notifiers require care. >=20 > Having actually resizable anonymous allocations (via mmap-hackery) allows > to reserve a big region in virtual address space and grow the > accessible/usable part on demand. Even if "/proc/sys/vm/overcommit_memory= " > is set to "never" under Linux, huge reservations will succeed. If there i= s > not enough memory when resizing (to populate parts of the reserved region= ), > trying to resize will fail. Only the actually used size is reserved in th= e > OS. >=20 > E.g., virtio-mem [1] wants to reserve big resizable memory regions and > grow the usable part on demand. I think this change is worth sending out > individually. Accompanied by a bunch of minor fixes and cleanups. >=20 > [1] https://lore.kernel.org/kvm/20191212171137.13872-1-david@redhat.com/ There's a few bits I've not understood from skimming the patches: a) Am I correct in thinking you PROT_NONE the extra space so you can gkrow/shrink it? b) What does kvm see - does it have a slot for the whole space or for only the used space? I ask because we found with virtiofs/DAX experiments that on Power, kvm gets upset if you give it a mapping with PROT_NONE. (That maybe less of an issue if you change the mapping after the slot is created). c) It's interesting this is keyed off the RAMBlock notifiers - do memory_listener's on the address space the block is mapped into get triggered? I'm wondering how vhost (and vhost-user) in particular see this. Dave >=20 > David Hildenbrand (13): > util: vfio-helpers: Factor out and fix processing of existings ram > blocks > exec: Factor out setting ram settings (madvise ...) into > qemu_ram_apply_settings() > exec: Reuse qemu_ram_apply_settings() in qemu_ram_remap() > exec: Drop "shared" parameter from ram_block_add() > util/mmap-alloc: Factor out calculation of pagesize to mmap_pagesize() > util/mmap-alloc: Factor out reserving of a memory region to > mmap_reserve() > util/mmap-alloc: Factor out populating of memory to mmap_populate() > util/mmap-alloc: Prepare for resizable mmaps > util/mmap-alloc: Implement resizable mmaps > numa: Introduce ram_block_notify_resized() and > ram_block_notifiers_support_resize() > util: vfio-helpers: Implement ram_block_resized() > util: oslib: Resizable anonymous allocations under POSIX > exec: Ram blocks with resizable anonymous allocations under POSIX >=20 > exec.c | 99 ++++++++++++++++++---- > hw/core/numa.c | 39 +++++++++ > include/exec/cpu-common.h | 3 + > include/exec/memory.h | 8 ++ > include/exec/ramlist.h | 4 + > include/qemu/mmap-alloc.h | 21 +++-- > include/qemu/osdep.h | 6 +- > stubs/ram-block.c | 20 ----- > util/mmap-alloc.c | 168 ++++++++++++++++++++++++-------------- > util/oslib-posix.c | 37 ++++++++- > util/oslib-win32.c | 14 ++++ > util/trace-events | 5 +- > util/vfio-helpers.c | 33 ++++---- > 13 files changed, 331 insertions(+), 126 deletions(-) >=20 > --=20 > 2.24.1 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK