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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 8EDECC76186 for ; Wed, 24 Jul 2019 20:42:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F80021841 for ; Wed, 24 Jul 2019 20:42:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728739AbfGXUmj (ORCPT ); Wed, 24 Jul 2019 16:42:39 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:34398 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727957AbfGXUmi (ORCPT ); Wed, 24 Jul 2019 16:42:38 -0400 Received: by mail-qt1-f194.google.com with SMTP id k10so46968717qtq.1 for ; Wed, 24 Jul 2019 13:42:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=0oDsp6PabiGgGzFV5AXKWcbAmWPliOqgciTu5AmtKko=; b=tDaiKmaTNNPBGlsrpJQ/s5SVEh+h+3rN6tiAhNKPgydCuSnXThnn3Qo/9uQDhKeiLO 8NMw/BD1xOpg0IbI1FK/2ar60TsolcJco21X3qSJKp8ga1PIZCRxq3VswkDb62WlIQkG k5al7a5q5vpQrlugsX3lzUVP6P2hpSdbtxuvdApEaT3uNAVFUfpUi97/qmIiSZDYRWRr iPGj0KlctfaOA4FB8jdEVdbNtGaSSvB7iePAlBSdAhHBxqq97GS5Xph0CId84tq+aKzl LwoCy/6pAaoLzzqwlyK0GfgQmhr/7niKsP5lMyDWkQ4owoeI3HQlXHNJiOzjx1BCIxxA NdeA== X-Gm-Message-State: APjAAAWizQ3ydxpcOXUg1BK+dbhdR8KsFZjtAGA5virLrTZsjnMqXJ3i Ua9/3+gOc/WrXY5573tswOT2pg== X-Google-Smtp-Source: APXvYqy1xyF8m0D0XrDjgh1Az86AClKVYNEKuVVVwKydA8wHTr4Opr/E4uUxsrcRi8Vs/vksPRXBLQ== X-Received: by 2002:ac8:5315:: with SMTP id t21mr59263152qtn.229.1564000957709; Wed, 24 Jul 2019 13:42:37 -0700 (PDT) Received: from redhat.com (bzq-79-181-91-42.red.bezeqint.net. [79.181.91.42]) by smtp.gmail.com with ESMTPSA id r14sm22913246qke.47.2019.07.24.13.42.32 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 24 Jul 2019 13:42:36 -0700 (PDT) Date: Wed, 24 Jul 2019 16:42:29 -0400 From: "Michael S. Tsirkin" To: Nitesh Narayan Lal Cc: Alexander Duyck , Alexander Duyck , kvm@vger.kernel.org, david@redhat.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, yang.zhang.wz@gmail.com, pagupta@redhat.com, riel@surriel.com, konrad.wilk@oracle.com, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com Subject: Re: [PATCH v2 QEMU] virtio-balloon: Provide a interface for "bubble hinting" Message-ID: <20190724164023-mutt-send-email-mst@kernel.org> References: <20190724165158.6685.87228.stgit@localhost.localdomain> <20190724171050.7888.62199.stgit@localhost.localdomain> <20190724150224-mutt-send-email-mst@kernel.org> <6218af96d7d55935f2cf607d47680edc9b90816e.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Jul 24, 2019 at 04:29:27PM -0400, Nitesh Narayan Lal wrote: > > On 7/24/19 4:18 PM, Alexander Duyck wrote: > > On Wed, 2019-07-24 at 15:02 -0400, Michael S. Tsirkin wrote: > >> On Wed, Jul 24, 2019 at 10:12:10AM -0700, Alexander Duyck wrote: > >>> From: Alexander Duyck > >>> > >>> Add support for what I am referring to as "bubble hinting". Basically the > >>> idea is to function very similar to how the balloon works in that we > >>> basically end up madvising the page as not being used. However we don't > >>> really need to bother with any deflate type logic since the page will be > >>> faulted back into the guest when it is read or written to. > >>> > >>> This is meant to be a simplification of the existing balloon interface > >>> to use for providing hints to what memory needs to be freed. I am assuming > >>> this is safe to do as the deflate logic does not actually appear to do very > >>> much other than tracking what subpages have been released and which ones > >>> haven't. > >>> > >>> Signed-off-by: Alexander Duyck > >>> --- > >>> hw/virtio/virtio-balloon.c | 40 +++++++++++++++++++++++ > >>> include/hw/virtio/virtio-balloon.h | 2 + > >>> include/standard-headers/linux/virtio_balloon.h | 1 + > >>> 3 files changed, 42 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > >>> index 2112874055fb..70c0004c0f88 100644 > >>> --- a/hw/virtio/virtio-balloon.c > >>> +++ b/hw/virtio/virtio-balloon.c > >>> @@ -328,6 +328,39 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v, > >>> balloon_stats_change_timer(s, 0); > >>> } > >>> > >>> +static void virtio_bubble_handle_output(VirtIODevice *vdev, VirtQueue *vq) > >>> +{ > >>> + VirtQueueElement *elem; > >>> + > >>> + while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) { > >>> + unsigned int i; > >>> + > >>> + for (i = 0; i < elem->in_num; i++) { > >>> + void *addr = elem->in_sg[i].iov_base; > >>> + size_t size = elem->in_sg[i].iov_len; > >>> + ram_addr_t ram_offset; > >>> + size_t rb_page_size; > >>> + RAMBlock *rb; > >>> + > >>> + if (qemu_balloon_is_inhibited()) > >>> + continue; > >>> + > >>> + rb = qemu_ram_block_from_host(addr, false, &ram_offset); > >>> + rb_page_size = qemu_ram_pagesize(rb); > >>> + > >>> + /* For now we will simply ignore unaligned memory regions */ > >>> + if ((ram_offset | size) & (rb_page_size - 1)) > >>> + continue; > >>> + > >>> + ram_block_discard_range(rb, ram_offset, size); > >> I suspect this needs to do like the migration type of > >> hinting and get disabled if page poisoning is in effect. > >> Right? > > Shouldn't something like that end up getting handled via > > qemu_balloon_is_inhibited, or did I miss something there? I assumed cases > > like that would end up setting qemu_balloon_is_inhibited to true, if that > > isn't the case then I could add some additional conditions. I would do it > > in about the same spot as the qemu_balloon_is_inhibited check. > I don't think qemu_balloon_is_inhibited() will take care of the page poisoning > situations. > If I am not wrong we may have to look to extend VIRTIO_BALLOON_F_PAGE_POISON > support as per Michael's suggestion. BTW upstream qemu seems to ignore VIRTIO_BALLOON_F_PAGE_POISON ATM. Which is probably a bug. Wei, could you take a look pls? > > > > > -- > Thanks > Nitesh