From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43959) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dea5V-0000Xs-WE for qemu-devel@nongnu.org; Mon, 07 Aug 2017 00:56:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dea5S-0007aH-R6 for qemu-devel@nongnu.org; Mon, 07 Aug 2017 00:56:22 -0400 Received: from mailout1.w1.samsung.com ([210.118.77.11]:54571) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dea5S-0007ZP-IE for qemu-devel@nongnu.org; Mon, 07 Aug 2017 00:56:18 -0400 From: Alexey Perevalov Message-id: <1e52da76-269f-020e-c9cf-adaaef30b59c@samsung.com> Date: Mon, 07 Aug 2017 07:49:11 +0300 MIME-version: 1.0 In-reply-to: <20170628190047.26159-24-dgilbert@redhat.com> Content-type: text/plain; charset="utf-8"; format="flowed" Content-transfer-encoding: 7bit Content-language: en-GB References: <20170628190047.26159-1-dgilbert@redhat.com> <20170628190047.26159-24-dgilbert@redhat.com> Subject: Re: [Qemu-devel] [RFC 23/29] vub+postcopy: madvises List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, marcandre.lureau@redhat.com, maxime.coquelin@redhat.com, mst@redhat.com, quintela@redhat.com, peterx@redhat.com, lvivier@redhat.com, aarcange@redhat.com On 06/28/2017 10:00 PM, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Clear the area and turn off THP. > > Signed-off-by: Dr. David Alan Gilbert > --- > contrib/libvhost-user/libvhost-user.c | 32 ++++++++++++++++++++++++++++++-- > 1 file changed, 30 insertions(+), 2 deletions(-) > > diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c > index 0658b6e847..ceddeac74f 100644 > --- a/contrib/libvhost-user/libvhost-user.c > +++ b/contrib/libvhost-user/libvhost-user.c > @@ -451,11 +451,39 @@ vu_set_mem_table_exec(VuDev *dev, VhostUserMsg *vmsg) > } > > if (dev->postcopy_listening) { > + int ret; > /* We should already have an open ufd need to mark each memory > * range as ufd. > - * Note: Do we need any madvises? Well it's not been accessed > - * yet, still probably need no THP to be safe, discard to be safe? > */ > + > + /* Discard any mapping we have here; note I can't use MADV_REMOVE > + * or fallocate to make the hole since I don't want to lose > + * data that's already arrived in the shared process. > + * TODO: How to do hugepage > + */ Hi, David, frankly saying, I stuck with my solution, and I have also another issues, but here I could suggest solution for hugepages. I think we could transmit a received pages bitmap in VHOST_USER_SET_MEM_TABLE (VhostUserMemoryRegion), but it will raise a compatibility issue, or introduce special message type for that and send it before VHOST_USER_SET_MEM_TABLE. So it will be possible to do fallocate on received bitmap basis, just skip already copied pages. If you wish, I could send patches, rebased on yours, for doing it. > + ret = madvise((void *)dev_region->mmap_addr, > + dev_region->size + dev_region->mmap_offset, > + MADV_DONTNEED); > + if (ret) { > + fprintf(stderr, > + "%s: Failed to madvise(DONTNEED) region %d: %s\n", > + __func__, i, strerror(errno)); > + } > + /* Turn off transparent hugepages so we dont get lose wakeups > + * in neighbouring pages. > + * TODO: Turn this backon later. > + */ > + ret = madvise((void *)dev_region->mmap_addr, > + dev_region->size + dev_region->mmap_offset, > + MADV_NOHUGEPAGE); > + if (ret) { > + /* Note: This can happen legally on kernels that are configured > + * without madvise'able hugepages > + */ > + fprintf(stderr, > + "%s: Failed to madvise(NOHUGEPAGE) region %d: %s\n", > + __func__, i, strerror(errno)); > + } > struct uffdio_register reg_struct; > /* Note: We might need to go back to using mmap_addr and > * len + mmap_offset for * huge pages, but then we do hope not to -- Best regards, Alexey Perevalov