From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50188) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1df7xl-0001ea-4v for qemu-devel@nongnu.org; Tue, 08 Aug 2017 13:06:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1df7xh-0003SQ-0g for qemu-devel@nongnu.org; Tue, 08 Aug 2017 13:06:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39486) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1df7xg-0003S7-Ob for qemu-devel@nongnu.org; Tue, 08 Aug 2017 13:06:32 -0400 Date: Tue, 8 Aug 2017 18:06:10 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20170808170610.GQ2081@work-vm> References: <20170628190047.26159-1-dgilbert@redhat.com> <20170628190047.26159-24-dgilbert@redhat.com> <1e52da76-269f-020e-c9cf-adaaef30b59c@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1e52da76-269f-020e-c9cf-adaaef30b59c@samsung.com> Subject: Re: [Qemu-devel] [RFC 23/29] vub+postcopy: madvises List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Perevalov Cc: 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 * Alexey Perevalov (a.perevalov@samsung.com) wrote: > 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. What we found works is that actually we don't need to do a discard - since we've only just done the mmap of the arena, nothing will be occupying it on the shared client, so we don't need to discard. We've had a postcopy migrate work now, with a few hacks we're still cleaning up, both on vhost-user-bridge and dpdk; so I'll get this updated and reposted. Dave > > + 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 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK