linux-kernel - Re: [PATCH v11 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE

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Message-ID: <fb67359c-3d19-f67f-ec47-3cf868b8d9e8@intel.com>
Date:   Tue, 13 Jun 2017 10:59:07 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Wei Wang <wei.w.wang@...el.com>
Cc:     virtio-dev@...ts.oasis-open.org, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, virtualization@...ts.linux-foundation.org,
        kvm@...r.kernel.org, linux-mm@...ck.org, david@...hat.com,
        cornelia.huck@...ibm.com, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, aarcange@...hat.com,
        amit.shah@...hat.com, pbonzini@...hat.com,
        liliang.opensource@...il.com, Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v11 3/6] virtio-balloon: VIRTIO_BALLOON_F_PAGE_CHUNKS

On 06/13/2017 10:56 AM, Michael S. Tsirkin wrote:
>> +/* The size of one page_bmap used to record inflated/deflated pages. */
>> +#define VIRTIO_BALLOON_PAGE_BMAP_SIZE	(8 * PAGE_SIZE)
> At this size, you probably want alloc_pages to avoid kmalloc
> overhead.

For slub, at least, kmalloc() just calls alloc_pages() basically
directly.  There's virtually no overhead.