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=-8.5 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,USER_AGENT_SANE_1 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 D054FC43331 for ; Tue, 31 Mar 2020 13:32:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 850872071A for ; Tue, 31 Mar 2020 13:32:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XrF/XffZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730865AbgCaNcW (ORCPT ); Tue, 31 Mar 2020 09:32:22 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:34100 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730216AbgCaNcW (ORCPT ); Tue, 31 Mar 2020 09:32:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585661539; 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:autocrypt:autocrypt; bh=sZeZGCdB0KUQHp66rbXcn3YhI5XBj4jlJKWVhIKJZDY=; b=XrF/XffZ+3I/pf4LSVT2sPINM4jXVWbKfL6TDoLtOXBVFGFriBLwiTV3Rm50RQ8LvTPYzw LZbGaeIDTGJf0/Rdn9UYXl62toB7mRwM1ROj4Sq7fqAICvmDkkqc57eIjkdOU85ZdGdOfE gRotdAAgS0DqzNFtcwnTaYpnsGelD6Y= 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-458-4CwtnLt1N7i7eOuybhwy0g-1; Tue, 31 Mar 2020 09:32:16 -0400 X-MC-Unique: 4CwtnLt1N7i7eOuybhwy0g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 38FD4190A7AC; Tue, 31 Mar 2020 13:32:14 +0000 (UTC) Received: from [10.36.114.0] (ovpn-114-0.ams2.redhat.com [10.36.114.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id E94031001B28; Tue, 31 Mar 2020 13:32:05 +0000 (UTC) Subject: Re: [RFC for Linux] virtio_balloon: Add VIRTIO_BALLOON_F_THP_ORDER to handle THP spilt issue To: "Michael S. Tsirkin" Cc: Hui Zhu , jasowang@redhat.com, akpm@linux-foundation.org, pagupta@redhat.com, mojha@codeaurora.org, namit@vmware.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Hui Zhu , Alexander Duyck References: <20200326031817-mutt-send-email-mst@kernel.org> <20200326054554-mutt-send-email-mst@kernel.org> <20200331091718-mutt-send-email-mst@kernel.org> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <02a393ce-c4b4-ede9-7671-76fa4c19097a@redhat.com> Date: Tue, 31 Mar 2020 15:32:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200331091718-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 31.03.20 15:24, Michael S. Tsirkin wrote: > On Tue, Mar 31, 2020 at 12:35:24PM +0200, David Hildenbrand wrote: >> On 26.03.20 10:49, Michael S. Tsirkin wrote: >>> On Thu, Mar 26, 2020 at 08:54:04AM +0100, David Hildenbrand wrote: >>>> >>>> >>>>> Am 26.03.2020 um 08:21 schrieb Michael S. Tsirkin : >>>>> >>>>> =EF=BB=BFOn Thu, Mar 12, 2020 at 09:51:25AM +0100, David Hildenbran= d wrote: >>>>>>> On 12.03.20 09:47, Michael S. Tsirkin wrote: >>>>>>> On Thu, Mar 12, 2020 at 09:37:32AM +0100, David Hildenbrand wrote= : >>>>>>>> 2. You are essentially stealing THPs in the guest. So the fastes= t >>>>>>>> mapping (THP in guest and host) is gone. The guest won't be able= to make >>>>>>>> use of THP where it previously was able to. I can imagine this i= mplies a >>>>>>>> performance degradation for some workloads. This needs a proper >>>>>>>> performance evaluation. >>>>>>> >>>>>>> I think the problem is more with the alloc_pages API. >>>>>>> That gives you exactly the given order, and if there's >>>>>>> a larger chunk available, it will split it up. >>>>>>> >>>>>>> But for balloon - I suspect lots of other users, >>>>>>> we do not want to stress the system but if a large >>>>>>> chunk is available anyway, then we could handle >>>>>>> that more optimally by getting it all in one go. >>>>>>> >>>>>>> >>>>>>> So if we want to address this, IMHO this calls for a new API. >>>>>>> Along the lines of >>>>>>> >>>>>>> struct page *alloc_page_range(gfp_t gfp, unsigned int min_orde= r, >>>>>>> unsigned int max_order, unsigned int *order) >>>>>>> >>>>>>> the idea would then be to return at a number of pages in the give= n >>>>>>> range. >>>>>>> >>>>>>> What do you think? Want to try implementing that? >>>>>> >>>>>> You can just start with the highest order and decrement the order = until >>>>>> your allocation succeeds using alloc_pages(), which would be enoug= h for >>>>>> a first version. At least I don't see the immediate need for a new >>>>>> kernel API. >>>>> >>>>> OK I remember now. The problem is with reclaim. Unless reclaim is >>>>> completely disabled, any of these calls can sleep. After it wakes u= p, >>>>> we would like to get the larger order that has become available >>>>> meanwhile. >>>>> >>>> >>>> Yes, but that=E2=80=98s a pure optimization IMHO. >>>> So I think we should do a trivial implementation first and then see = what we gain from a new allocator API. Then we might also be able to just= ify it using real numbers. >>>> >>> >>> Well how do you propose implement the necessary semantics? >>> I think we are both agreed that alloc_page_range is more or >>> less what's necessary anyway - so how would you approximate it >>> on top of existing APIs? >> >> Looking at drivers/misc/vmw_balloon.c:vmballoon_inflate(), it first >> tries to allocate huge pages using >> >> alloc_pages(__GFP_HIGHMEM|__GFP_NOWARN| __GFP_NOMEMALLOC,=20 >> VMW_BALLOON_2M_ORDER) >> >> And then falls back to 4k allocations (balloon_page_alloc()) in case >> allocation fails. >> >> I'm roughly thinking of something like the following, but with an >> optimized reporting interface/bigger pfn array so we can report > >> 1MB at a time. Also, it might make sense to remember the order that >> succeeded across some fill_balloon() calls. >> >> Don't even expect it to compile ... >> >> >> >> >From 4305f989672ccca4be9293e6d4167e929f3e299b Mon Sep 17 00:00:00 200= 1 >> From: David Hildenbrand >> Date: Tue, 31 Mar 2020 12:28:07 +0200 >> Subject: [PATCH RFC] tmp >> >> Signed-off-by: David Hildenbrand >> --- >> drivers/virtio/virtio_balloon.c | 38 ++++++++++++++++++-------- >> include/linux/balloon_compaction.h | 7 ++++- >> mm/balloon_compaction.c | 43 +++++++++++++++++++++++------= - >> 3 files changed, 67 insertions(+), 21 deletions(-) >> >> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_b= alloon.c >> index 8511d258dbb4..0660b1b988f0 100644 >> --- a/drivers/virtio/virtio_balloon.c >> +++ b/drivers/virtio/virtio_balloon.c >> @@ -187,7 +187,7 @@ int virtballoon_free_page_report(struct page_repor= ting_dev_info *pr_dev_info, >> } >> =20 >> static void set_page_pfns(struct virtio_balloon *vb, >> - __virtio32 pfns[], struct page *page) >> + __virtio32 pfns[], struct page *page, int order) >> { >> unsigned int i; >> =20 >> @@ -197,7 +197,7 @@ static void set_page_pfns(struct virtio_balloon *v= b, >> * Set balloon pfns pointing at this page. >> * Note that the first pfn points at start of the page. >> */ >> - for (i =3D 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++) >> + for (i =3D 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE * (1 << order); i++) >> pfns[i] =3D cpu_to_virtio32(vb->vdev, >> page_to_balloon_pfn(page) + i); >> } >> @@ -205,6 +205,7 @@ static void set_page_pfns(struct virtio_balloon *v= b, >> static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) >> { >> unsigned num_allocated_pages; >> + int order =3D MAX_ORDER - 1; >> unsigned num_pfns; >> struct page *page; >> LIST_HEAD(pages); >> @@ -212,9 +213,20 @@ static unsigned fill_balloon(struct virtio_balloo= n *vb, size_t num) >> /* We can only do one array worth at a time. */ >> num =3D min(num, ARRAY_SIZE(vb->pfns)); >> =20 >> + /* >> + * Note: we will currently never allocate more than 1MB due to the >> + * pfn array size, so we will not allocate MAX_ORDER - 1 ... >> + */ >> + >> for (num_pfns =3D 0; num_pfns < num; >> - num_pfns +=3D VIRTIO_BALLOON_PAGES_PER_PAGE) { >> - struct page *page =3D balloon_page_alloc(); >> + num_pfns +=3D VIRTIO_BALLOON_PAGES_PER_PAGE * (1 << order)) { >> + const unsigned long remaining =3D num - num_pfns; >> + >> + order =3D MIN(order, >> + get_order(remaining << VIRTIO_BALLOON_PFN_SHIFT)); >> + if ((1 << order) * VIRTIO_BALLOON_PAGES_PER_PAGE > remaining) >> + order--; >> + page =3D balloon_pages_alloc(order); >> =20 >> if (!page) { >> dev_info_ratelimited(&vb->vdev->dev, >> @@ -225,6 +237,8 @@ static unsigned fill_balloon(struct virtio_balloon= *vb, size_t num) >> break; >> } >> =20 >> + /* Continue with the actual order that succeeded. */ >> + order =3D page_private(page); >> balloon_page_push(&pages, page); >> } >> =20 >> @@ -233,14 +247,16 @@ static unsigned fill_balloon(struct virtio_ballo= on *vb, size_t num) >> vb->num_pfns =3D 0; >> =20 >> while ((page =3D balloon_page_pop(&pages))) { >> + order =3D page_order(page); >> + /* enqueuing will split the page and clear the order */ >> balloon_page_enqueue(&vb->vb_dev_info, page); >> =20 >> - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); >> - vb->num_pages +=3D VIRTIO_BALLOON_PAGES_PER_PAGE; >> + set_page_pfns(vb, vb->pfns + vb->num_pfns, page, order); >> + vb->num_pages +=3D VIRTIO_BALLOON_PAGES_PER_PAGE * (1 << order); >> if (!virtio_has_feature(vb->vdev, >> VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) >> - adjust_managed_page_count(page, -1); >> - vb->num_pfns +=3D VIRTIO_BALLOON_PAGES_PER_PAGE; >> + adjust_managed_page_count(page, -1 * (1 << order)); >> + vb->num_pfns +=3D VIRTIO_BALLOON_PAGES_PER_PAGE * (1 << order); >> } >> =20 >> num_allocated_pages =3D vb->num_pfns; >> @@ -284,7 +300,7 @@ static unsigned leak_balloon(struct virtio_balloon= *vb, size_t num) >> page =3D balloon_page_dequeue(vb_dev_info); >> if (!page) >> break; >> - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); >> + set_page_pfns(vb, vb->pfns + vb->num_pfns, page, 0); >> list_add(&page->lru, &pages); >> vb->num_pages -=3D VIRTIO_BALLOON_PAGES_PER_PAGE; >> } >> @@ -786,7 +802,7 @@ static int virtballoon_migratepage(struct balloon_= dev_info *vb_dev_info, >> __count_vm_event(BALLOON_MIGRATE); >> spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); >> vb->num_pfns =3D VIRTIO_BALLOON_PAGES_PER_PAGE; >> - set_page_pfns(vb, vb->pfns, newpage); >> + set_page_pfns(vb, vb->pfns, newpage, 0); >> tell_host(vb, vb->inflate_vq); >> =20 >> /* balloon's page migration 2nd step -- deflate "page" */ >> @@ -794,7 +810,7 @@ static int virtballoon_migratepage(struct balloon_= dev_info *vb_dev_info, >> balloon_page_delete(page); >> spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); >> vb->num_pfns =3D VIRTIO_BALLOON_PAGES_PER_PAGE; >> - set_page_pfns(vb, vb->pfns, page); >> + set_page_pfns(vb, vb->pfns, page, 0); >> tell_host(vb, vb->deflate_vq); >> =20 >> mutex_unlock(&vb->balloon_lock); >> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloo= n_compaction.h >> index 338aa27e4773..ed93fe5704d1 100644 >> --- a/include/linux/balloon_compaction.h >> +++ b/include/linux/balloon_compaction.h >> @@ -60,7 +60,7 @@ struct balloon_dev_info { >> struct inode *inode; >> }; >> =20 >> -extern struct page *balloon_page_alloc(void); >> +extern struct page *balloon_pages_alloc(int order); >> extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, >> struct page *page); >> extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_d= ev_info); >> @@ -78,6 +78,11 @@ static inline void balloon_devinfo_init(struct ball= oon_dev_info *balloon) >> balloon->inode =3D NULL; >> } >> =20 >> +static inline struct page *balloon_page_alloc(void) >> +{ >> + return balloon_pages_alloc(0); >> +} >> + >> #ifdef CONFIG_BALLOON_COMPACTION >> extern const struct address_space_operations balloon_aops; >> extern bool balloon_page_isolate(struct page *page, >> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c >> index 26de020aae7b..067810b32813 100644 >> --- a/mm/balloon_compaction.c >> +++ b/mm/balloon_compaction.c >> @@ -112,23 +112,35 @@ size_t balloon_page_list_dequeue(struct balloon_= dev_info *b_dev_info, >> EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); >> =20 >> /* >> - * balloon_page_alloc - allocates a new page for insertion into the b= alloon >> - * page list. >> + * balloon_pages_alloc - allocates a new page (of at most the given o= rder) >> + * for insertion into the balloon page list. >> * >> * Driver must call this function to properly allocate a new balloon = page. >> * Driver must call balloon_page_enqueue before definitively removing= the page >> * from the guest system. >> * >> + * Will fall back to smaller orders if allocation fails. The order of= the >> + * allocated page is stored in page->private. >> + * >> * Return: struct page for the allocated page or NULL on allocation f= ailure. >> */ >> -struct page *balloon_page_alloc(void) >> +struct page *balloon_pages_alloc(int order) >> { >> - struct page *page =3D alloc_page(balloon_mapping_gfp_mask() | >> - __GFP_NOMEMALLOC | __GFP_NORETRY | >> - __GFP_NOWARN); >> - return page; >> + struct page *page; >> + >> + while (order >=3D 0) { >> + page =3D alloc_pages(balloon_mapping_gfp_mask() | >> + __GFP_NOMEMALLOC | __GFP_NORETRY | >> + __GFP_NOWARN, order); >> + if (page) { >> + set_page_private(page, order); >> + return page; >> + } >> + order--; >> + } >> + return NULL; >> } >> -EXPORT_SYMBOL_GPL(balloon_page_alloc); >> +EXPORT_SYMBOL_GPL(balloon_pages_alloc); >> =20 >> /* >> * balloon_page_enqueue - inserts a new page into the balloon page li= st. >=20 >=20 > I think this will try to invoke direct reclaim from the first iteration > to free up the max order. %__GFP_NORETRY: The VM implementation will try only very lightweight memory direct reclaim to get some memory under memory pressure (thus it can sleep). It will avoid disruptive actions like OOM killer. Certainly good enough for a first version I would say, no? Looking at the vmware balloon, they don't even set __GFP_NORETRY. --=20 Thanks, David / dhildenb