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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 9E3D1C3B186 for ; Tue, 11 Feb 2020 11:47:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 56D2F20848 for ; Tue, 11 Feb 2020 11:47:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ahV1aY8X" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56D2F20848 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 02A146B02B8; Tue, 11 Feb 2020 06:47:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 002376B02B9; Tue, 11 Feb 2020 06:47:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E598C6B02BA; Tue, 11 Feb 2020 06:47:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0056.hostedemail.com [216.40.44.56]) by kanga.kvack.org (Postfix) with ESMTP id CCDB36B02B8 for ; Tue, 11 Feb 2020 06:47:57 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6174C181AEF00 for ; Tue, 11 Feb 2020 11:47:57 +0000 (UTC) X-FDA: 76477672194.23.fifth15_62538d3c8dc1e X-HE-Tag: fifth15_62538d3c8dc1e X-Filterd-Recvd-Size: 10081 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Tue, 11 Feb 2020 11:47:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581421675; 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=3XROZAoE8uA3ebrIf8N8DYUE+CZDamcRxNyr03wVIUY=; b=ahV1aY8XI8FY1nGcLBNbVNVRaOmDuqCNWcpT662/SBIn34g7UZJLaUJd6pMLqnH5vHmOvo sp+ZfQfUVVzEvbLtG/uFTsAT6DPq2jgoBgy+M921URA1QNjzkE12Cstjz4554w7p/O/dRq fZ5qDpwArkUsMduisPoJJEfIB++VSa0= Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-222-xtDvm71hMo6I9rAIiPQrYQ-1; Tue, 11 Feb 2020 06:47:51 -0500 Received: by mail-qt1-f200.google.com with SMTP id p12so6385539qtu.6 for ; Tue, 11 Feb 2020 03:47:51 -0800 (PST) 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=UZ+e+/Q/bgo4cstCyNeXCa8O9APumSBN7bEnx6koZUg=; b=OZMGzW3ODsoD6Ry66f0S31v60KVKg2s921LhgebY4gKrRVrl7l1nU4iDe293ANUTtL WHpGegGNu1YivJSt6vN5EbxUxxOedrFcTLH2pnZeKJO/gYguzoujV1866/FEimnRUp1a 6+W/yd8fQnZ/1I9KOf3JjXkhkWskPoVmFsHDEHJ9bwQzgsgcWcLvUHfZHTWf0FNMEjVH hzUgep+EaucG7ySZDw2IFmAd7Y5bo0s7KeO7xJnhdJ1qhncVrCdASkS28sijn3XzbRtR q8skDpKPWYQx+NvrP70HbF3MGPY4GLMsoJ9hvicASs6ge9Eu7snTKkKZGd3ItcwTBZ+9 fHKg== X-Gm-Message-State: APjAAAWxpcRIHYKmtmt0Ippfxg1COtR8inBA1XQKInhI7K+Obve54axz CKPeIVHxXon3RjJsmueN6YMnetwmEEMB24pieAT9IpGSGoTkY1IRJpYJ9d2g5EA184mWXV6L10M ZqkTCO86mYu4= X-Received: by 2002:aed:2643:: with SMTP id z61mr2015605qtc.49.1581421671395; Tue, 11 Feb 2020 03:47:51 -0800 (PST) X-Google-Smtp-Source: APXvYqx6c+QCmz/2JPA19VAPKWAg4SiME/3B79iYqvLXcvvmNlRQinhDVfltdEKaQ6b3MRvo1ed81g== X-Received: by 2002:aed:2643:: with SMTP id z61mr2015587qtc.49.1581421671068; Tue, 11 Feb 2020 03:47:51 -0800 (PST) Received: from redhat.com (bzq-79-176-41-183.red.bezeqint.net. [79.176.41.183]) by smtp.gmail.com with ESMTPSA id o6sm1783902qkk.53.2020.02.11.03.47.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Feb 2020 03:47:50 -0800 (PST) Date: Tue, 11 Feb 2020 06:47:44 -0500 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: Alexander Duyck , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz, yang.zhang.wz@gmail.com, nitesh@redhat.com, konrad.wilk@oracle.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com, osalvador@suse.de Subject: Re: [PATCH v16.1 6/9] virtio-balloon: Add support for providing free page reports to host Message-ID: <20200211063441-mutt-send-email-mst@kernel.org> References: <20200122173040.6142.39116.stgit@localhost.localdomain> <20200122174347.6142.92803.stgit@localhost.localdomain> MIME-Version: 1.0 In-Reply-To: X-MC-Unique: xtDvm71hMo6I9rAIiPQrYQ-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-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 11, 2020 at 12:03:57PM +0100, David Hildenbrand wrote: > On 22.01.20 18:43, Alexander Duyck wrote: > > From: Alexander Duyck > >=20 > > Add support for the page reporting feature provided by virtio-balloon. > > Reporting differs from the regular balloon functionality in that is is > > much less durable than a standard memory balloon. Instead of creating a > > list of pages that cannot be accessed the pages are only inaccessible > > while they are being indicated to the virtio interface. Once the > > interface has acknowledged them they are placed back into their respect= ive > > free lists and are once again accessible by the guest system. > >=20 > > Unlike a standard balloon we don't inflate and deflate the pages. Inste= ad > > we perform the reporting, and once the reporting is completed it is > > assumed that the page has been dropped from the guest and will be fault= ed > > back in the next time the page is accessed. > >=20 > > Acked-by: Michael S. Tsirkin > > Reviewed-by: David Hildenbrand > > Signed-off-by: Alexander Duyck > > --- > > drivers/virtio/Kconfig | 1 + > > drivers/virtio/virtio_balloon.c | 64 +++++++++++++++++++++++++++= ++++++++ > > include/uapi/linux/virtio_balloon.h | 1 + > > 3 files changed, 66 insertions(+) > >=20 > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > > index 078615cf2afc..4b2dd8259ff5 100644 > > --- a/drivers/virtio/Kconfig > > +++ b/drivers/virtio/Kconfig > > @@ -58,6 +58,7 @@ config VIRTIO_BALLOON > > =09tristate "Virtio balloon driver" > > =09depends on VIRTIO > > =09select MEMORY_BALLOON > > +=09select PAGE_REPORTING > > =09---help--- > > =09 This driver supports increasing and decreasing the amount > > =09 of memory within a KVM guest. > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_ba= lloon.c > > index 40bb7693e3de..a07b9e18a292 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -19,6 +19,7 @@ > > #include > > #include > > #include > > +#include > > =20 > > /* > > * Balloon device works in 4K page units. So each page is pointed to = by > > @@ -47,6 +48,7 @@ enum virtio_balloon_vq { > > =09VIRTIO_BALLOON_VQ_DEFLATE, > > =09VIRTIO_BALLOON_VQ_STATS, > > =09VIRTIO_BALLOON_VQ_FREE_PAGE, > > +=09VIRTIO_BALLOON_VQ_REPORTING, > > =09VIRTIO_BALLOON_VQ_MAX > > }; > > =20 > > @@ -114,6 +116,10 @@ struct virtio_balloon { > > =20 > > =09/* To register a shrinker to shrink memory upon memory pressure */ > > =09struct shrinker shrinker; > > + > > +=09/* Free page reporting device */ > > +=09struct virtqueue *reporting_vq; > > +=09struct page_reporting_dev_info pr_dev_info; > > }; > > =20 > > static struct virtio_device_id id_table[] =3D { > > @@ -153,6 +159,33 @@ static void tell_host(struct virtio_balloon *vb, s= truct virtqueue *vq) > > =20 > > } > > =20 > > +int virtballoon_free_page_report(struct page_reporting_dev_info *pr_de= v_info, > > +=09=09=09=09 struct scatterlist *sg, unsigned int nents) > > +{ > > +=09struct virtio_balloon *vb =3D > > +=09=09container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); > > +=09struct virtqueue *vq =3D vb->reporting_vq; > > +=09unsigned int unused, err; > > + > > +=09/* We should always be able to add these buffers to an empty queue.= */ > > +=09err =3D virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_N= OWARN); > > + > > +=09/* > > +=09 * In the extremely unlikely case that something has occurred and w= e > > +=09 * are able to trigger an error we will simply display a warning > > +=09 * and exit without actually processing the pages. > > +=09 */ > > +=09if (WARN_ON_ONCE(err)) > > +=09=09return err; > > + > > +=09virtqueue_kick(vq); > > + > > +=09/* When host has read buffer, this completes via balloon_ack */ > > +=09wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); > > + > > +=09return 0; > > +} >=20 >=20 > Did you see the discussion regarding unifying handling of > inflate/deflate/free_page_hinting_free_page_reporting, requested by > Michael? I think free page reporting is special and shall be left alone. Not sure what do you mean by "left alone here". Could you clarify? > VIRTIO_BALLOON_F_REPORTING is nothing but a more advanced inflate, right > (sg, inflate based on size - not "virtio pages")? Not exactly - it's also initiated by guest as opposed to host, and not guided by the ballon size request set by the host. And uses a dedicated queue to avoid blocking other functionality ... I really think this is more like an inflate immediately followed by deflate= . > And you rely on > deflates not being required before reusing an inflated page. >=20 > I suggest the following: >=20 > /* New interface (+ 2 virtqueues) to inflate/deflate using a SG */ > VIRTIO_BALLOON_F_SG > /* > * No need to deflate when reusing pages (once the inflate request was > * processed). Applies to all inflate queues. > */ > VIRTIO_BALLOON_F_OPTIONAL_DEFLATE >=20 > And two new virtqueues >=20 > VIRTIO_BALLOON_VQ_INFLATE_SG > VIRTIO_BALLOON_VQ_DEFLATE_SG >=20 >=20 > Your feature would depend on VIRTIO_BALLOON_F_SG && > VIRTIO_BALLOON_F_OPTIONAL_DEFLATE. VIRTIO_BALLOON_F_OPTIONAL_DEFLATE > could be reused to avoid deflating on certain events (e.g., from > OOM/shrinker). >=20 > Thoughts? I'd rather wait until we have a usecase and preferably a POC showing it helps before we add optional deflate ... For now I personally am fine with just making this go ahead as is, and imply SG and OPTIONAL_DEFLATE just for this VQ. Do you feel strongly we need to bring this up to a TC vote? It means spec patch needs to be written, but it does not have to be a big patch ... > --=20 > Thanks, >=20 > David / dhildenb