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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 65CF8C04AB5 for ; Mon, 3 Jun 2019 22:38:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AA2326A01 for ; Mon, 3 Jun 2019 22:38:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="s9+aMnx6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726179AbfFCWij (ORCPT ); Mon, 3 Jun 2019 18:38:39 -0400 Received: from mail-it1-f196.google.com ([209.85.166.196]:35642 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726025AbfFCWij (ORCPT ); Mon, 3 Jun 2019 18:38:39 -0400 Received: by mail-it1-f196.google.com with SMTP id n189so10844315itd.0; Mon, 03 Jun 2019 15:38:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=F/ixDeQhQV0jkM+ZLEc/zUFxrkTvZoI9aB593YmsPiA=; b=s9+aMnx6B3R0hLSkCU1J6r+p1AiMsWy/lS4s0oth8CJJfttuYrqWdaFXKQUggrJ0B/ sF3/n1/6QUBSqlLcDes5E5PYyl+oeAsV0DGtwnGzLigTlDdztk1cCIxyrNvQKt9Vo9Zd G7egM7/Mm1B3cChhYLxz7qmiYxEd9ygcusCLtAstLWvOZeX6GzpJLVoa/yyT6fWJ8rEE v4siPNXfVWM79HhrQPBHunnd5GQRrfmWoSQW/tgpbaUz8Bg/S1j4BLFmh01yJEhczXam rtpTOEqIlv8e//gYzQcDQqVG2RBXwnCMbSnSDZ65KAWWS+gZE+UBhQqJQOS+rRCiSn5b YRnQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=F/ixDeQhQV0jkM+ZLEc/zUFxrkTvZoI9aB593YmsPiA=; b=NfXSGYats/EAuZLCRlNlRaAMgQwaRkjnV407sVTRce85s9auzlkcqajedi+OvUvwMD W0jGRvfXprQNDVw+1+TnGIekK7707j8lfo6UYh7nWvIg6rbuYopzDAFPdrv4lx4IFYzC Y+93pNqXI6Xs4AeKk9q527eypqZNWk4fN6ADE1RidcWDHwcKQGUkCkiouy/YdGigct9x GgheOljadAeZyCgn7Nk61eEpswQh/KycSQsP2JQ4bSwmruh2MrhlSWoyFSwZZtLsHAdc 0zxJVr1g1R2xWFvoH3vhqILibM3x3QsnwnhxHhxLB7z097y3MvOlJDzlo1iNTDOQTdlR V6jw== X-Gm-Message-State: APjAAAVlwf77b0eJi732uCL+LV9SzrlwQXI1QcPIddyqkzz+CzzSN8g8 79xPGqYfA7S2wy0IQMM9vfeTfcfIXEcwEIQoj9M= X-Google-Smtp-Source: APXvYqxE3pqRl68z5nHb341KBeHZIiVFd5DLcpA0OiQW5aDXbSqBg02oNx5KzeRRPXKtMYy6PK+00mxJhVAMM2gxC80= X-Received: by 2002:a02:5502:: with SMTP id e2mr18612138jab.87.1559601517930; Mon, 03 Jun 2019 15:38:37 -0700 (PDT) MIME-Version: 1.0 References: <20190603170306.49099-1-nitesh@redhat.com> <20190603170306.49099-3-nitesh@redhat.com> In-Reply-To: <20190603170306.49099-3-nitesh@redhat.com> From: Alexander Duyck Date: Mon, 3 Jun 2019 15:38:26 -0700 Message-ID: Subject: Re: [RFC][Patch v10 2/2] virtio-balloon: page_hinting: reporting to the host To: Nitesh Narayan Lal Cc: kvm list , LKML , linux-mm , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , David Hildenbrand , "Michael S. Tsirkin" , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jun 3, 2019 at 10:04 AM Nitesh Narayan Lal wrote: > > Enables the kernel to negotiate VIRTIO_BALLOON_F_HINTING feature with the > host. If it is available and page_hinting_flag is set to true, page_hinting > is enabled and its callbacks are configured along with the max_pages count > which indicates the maximum number of pages that can be isolated and hinted > at a time. Currently, only free pages of order >= (MAX_ORDER - 2) are > reported. To prevent any false OOM max_pages count is set to 16. > > By default page_hinting feature is enabled and gets loaded as soon > as the virtio-balloon driver is loaded. However, it could be disabled > by writing the page_hinting_flag which is a virtio-balloon parameter. > > Signed-off-by: Nitesh Narayan Lal > --- > drivers/virtio/virtio_balloon.c | 112 +++++++++++++++++++++++++++- > include/uapi/linux/virtio_balloon.h | 14 ++++ > 2 files changed, 125 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index f19061b585a4..40f09ea31643 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -31,6 +31,7 @@ > #include > #include > #include > +#include > > /* > * Balloon device works in 4K page units. So each page is pointed to by > @@ -48,6 +49,7 @@ > /* The size of a free page block in bytes */ > #define VIRTIO_BALLOON_FREE_PAGE_SIZE \ > (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT)) > +#define VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES 16 > > #ifdef CONFIG_BALLOON_COMPACTION > static struct vfsmount *balloon_mnt; > @@ -58,6 +60,7 @@ enum virtio_balloon_vq { > VIRTIO_BALLOON_VQ_DEFLATE, > VIRTIO_BALLOON_VQ_STATS, > VIRTIO_BALLOON_VQ_FREE_PAGE, > + VIRTIO_BALLOON_VQ_HINTING, > VIRTIO_BALLOON_VQ_MAX > }; > > @@ -67,7 +70,8 @@ enum virtio_balloon_config_read { > > struct virtio_balloon { > struct virtio_device *vdev; > - struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; > + struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq, > + *hinting_vq; > > /* Balloon's own wq for cpu-intensive work items */ > struct workqueue_struct *balloon_wq; > @@ -125,6 +129,9 @@ struct virtio_balloon { > > /* To register a shrinker to shrink memory upon memory pressure */ > struct shrinker shrinker; > + > + /* object pointing at the array of isolated pages ready for hinting */ > + struct hinting_data *hinting_arr; Just make this an array of size VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES. It will save a bunch of complexity later. > }; > > static struct virtio_device_id id_table[] = { > @@ -132,6 +139,85 @@ static struct virtio_device_id id_table[] = { > { 0 }, > }; > > +#ifdef CONFIG_PAGE_HINTING Instead of having CONFIG_PAGE_HINTING enable this, maybe we should have virtio-balloon enable CONFIG_PAGE_HINTING. > +struct virtio_balloon *hvb; > +bool page_hinting_flag = true; > +module_param(page_hinting_flag, bool, 0444); > +MODULE_PARM_DESC(page_hinting_flag, "Enable page hinting"); > + > +static bool virtqueue_kick_sync(struct virtqueue *vq) > +{ > + u32 len; > + > + if (likely(virtqueue_kick(vq))) { > + while (!virtqueue_get_buf(vq, &len) && > + !virtqueue_is_broken(vq)) > + cpu_relax(); > + return true; Is this a synchronous setup? It seems kind of wasteful to have a thread busy waiting here like this. It might make more sense to just make this work like the other balloon queues and have a wait event with a wake up in the interrupt handler for the queue. > + } > + return false; > +} > + > +static void page_hinting_report(int entries) > +{ > + struct scatterlist sg; > + struct virtqueue *vq = hvb->hinting_vq; > + int err = 0; > + struct hinting_data *hint_req; > + u64 gpaddr; > + > + hint_req = kmalloc(sizeof(*hint_req), GFP_KERNEL); > + if (!hint_req) > + return; Why do we need another allocation here? Couldn't you just allocate hint_req on the stack and then use that? I think we might be doing too much here. All this really needs to look like is something along the lines of tell_host() minus the wait_event. > + gpaddr = virt_to_phys(hvb->hinting_arr); > + hint_req->phys_addr = cpu_to_virtio64(hvb->vdev, gpaddr); > + hint_req->size = cpu_to_virtio32(hvb->vdev, entries); > + sg_init_one(&sg, hint_req, sizeof(*hint_req)); > + err = virtqueue_add_outbuf(vq, &sg, 1, hint_req, GFP_KERNEL); > + if (!err) > + virtqueue_kick_sync(hvb->hinting_vq); > + > + kfree(hint_req); > +} > + > +int page_hinting_prepare(void) > +{ > + hvb->hinting_arr = kmalloc_array(VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES, > + sizeof(*hvb->hinting_arr), GFP_KERNEL); > + if (!hvb->hinting_arr) > + return -ENOMEM; > + return 0; > +} > + Why make the hinting_arr a dynamic allocation? You should probably just make it a static array within the virtio_balloon structure. Then you don't have the risk of an allocation failing and messing up the hints. > +void hint_pages(struct list_head *pages) > +{ > + struct page *page, *next; > + unsigned long pfn; > + int idx = 0, order; > + > + list_for_each_entry_safe(page, next, pages, lru) { > + pfn = page_to_pfn(page); > + order = page_private(page); > + hvb->hinting_arr[idx].phys_addr = pfn << PAGE_SHIFT; > + hvb->hinting_arr[idx].size = (1 << order) * PAGE_SIZE; > + idx++; > + } > + page_hinting_report(idx); > +} > + Getting back to my suggestion from earlier today. It might make sense to not bother with the PAGE_SHIFT or PAGE_SIZE multiplication if you just record everything in VIRTIO_BALLOON_PAGES intead of using the actual address and size. > +void page_hinting_cleanup(void) > +{ > + kfree(hvb->hinting_arr); > +} > + Same comment here. Make this array a part of virtio_balloon and you don't have to free it. > +static const struct page_hinting_cb hcb = { > + .prepare = page_hinting_prepare, > + .hint_pages = hint_pages, > + .cleanup = page_hinting_cleanup, > + .max_pages = VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES, > +}; With the above changes prepare and cleanup can be dropped. > +#endif > + > static u32 page_to_balloon_pfn(struct page *page) > { > unsigned long pfn = page_to_pfn(page); > @@ -488,6 +574,7 @@ static int init_vqs(struct virtio_balloon *vb) > names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; > names[VIRTIO_BALLOON_VQ_STATS] = NULL; > names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; > + names[VIRTIO_BALLOON_VQ_HINTING] = NULL; > > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > names[VIRTIO_BALLOON_VQ_STATS] = "stats"; > @@ -499,11 +586,18 @@ static int init_vqs(struct virtio_balloon *vb) > callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; > } > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { > + names[VIRTIO_BALLOON_VQ_HINTING] = "hinting_vq"; > + callbacks[VIRTIO_BALLOON_VQ_HINTING] = NULL; > + } > err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, > vqs, callbacks, names, NULL, NULL); > if (err) > return err; > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) > + vb->hinting_vq = vqs[VIRTIO_BALLOON_VQ_HINTING]; > + > vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; > vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > @@ -942,6 +1036,14 @@ static int virtballoon_probe(struct virtio_device *vdev) > if (err) > goto out_del_balloon_wq; > } > + > +#ifdef CONFIG_PAGE_HINTING > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING) && > + page_hinting_flag) { > + hvb = vb; > + page_hinting_enable(&hcb); > + } > +#endif > virtio_device_ready(vdev); > > if (towards_target(vb)) > @@ -989,6 +1091,12 @@ static void virtballoon_remove(struct virtio_device *vdev) > destroy_workqueue(vb->balloon_wq); > } > > +#ifdef CONFIG_PAGE_HINTING > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { > + hvb = NULL; > + page_hinting_disable(); > + } > +#endif > remove_common(vb); > #ifdef CONFIG_BALLOON_COMPACTION > if (vb->vb_dev_info.inode) > @@ -1043,8 +1151,10 @@ static unsigned int features[] = { > VIRTIO_BALLOON_F_MUST_TELL_HOST, > VIRTIO_BALLOON_F_STATS_VQ, > VIRTIO_BALLOON_F_DEFLATE_ON_OOM, > + VIRTIO_BALLOON_F_HINTING, > VIRTIO_BALLOON_F_FREE_PAGE_HINT, > VIRTIO_BALLOON_F_PAGE_POISON, > + VIRTIO_BALLOON_F_HINTING, > }; > > static struct virtio_driver virtio_balloon_driver = { > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h > index a1966cd7b677..25e4f817c660 100644 > --- a/include/uapi/linux/virtio_balloon.h > +++ b/include/uapi/linux/virtio_balloon.h > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > > /* The feature bitmap for virtio balloon */ > #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */ > @@ -36,6 +37,7 @@ > #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */ > #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */ > #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ > +#define VIRTIO_BALLOON_F_HINTING 5 /* Page hinting virtqueue */ > > /* Size of a PFN in the balloon interface. */ > #define VIRTIO_BALLOON_PFN_SHIFT 12 > @@ -108,4 +110,16 @@ struct virtio_balloon_stat { > __virtio64 val; > } __attribute__((packed)); > > +#ifdef CONFIG_PAGE_HINTING > +/* > + * struct hinting_data- holds the information associated with hinting. > + * @phys_add: physical address associated with a page or the array holding > + * the array of isolated pages. > + * @size: total size associated with the phys_addr. > + */ > +struct hinting_data { > + __virtio64 phys_addr; > + __virtio32 size; > +}; So in order to avoid errors this should either have "__attribute__((packed))" added or it should be changed to a pair of u32 or u64 values so that it will always be the same size regardless of what platform it is built on. > +#endif > #endif /* _LINUX_VIRTIO_BALLOON_H */ > -- > 2.21.0 >