Hi Maxime, > -----Original Message----- > From: Maxime Coquelin [mailto:maxime.coque...@redhat.com] > Sent: Tuesday, February 20, 2018 4:45 AM > To: Tan, Jianfeng; dev@dpdk.org > Cc: y...@fridaylinux.org > Subject: Re: [PATCH 4/4] vhost: avoid populate guest memory > > Hi Jianfeng, > > On 02/14/2018 05:01 AM, Jianfeng Tan wrote: > > It's not necessary to polulate guest memory from vhost side. > > > > Cc: maxime.coque...@redhat.com > > Cc: y...@fridaylinux.org > > > > Signed-off-by: Jianfeng Tan <jianfeng....@intel.com> > > --- > > lib/librte_vhost/vhost_user.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c > > index 90ed211..9bd0391 100644 > > --- a/lib/librte_vhost/vhost_user.c > > +++ b/lib/librte_vhost/vhost_user.c > > @@ -644,6 +644,7 @@ vhost_user_set_mem_table(struct virtio_net *dev, > struct VhostUserMsg *pmsg) > > uint64_t mmap_offset; > > uint64_t alignment; > > uint32_t i; > > + int populate; > > int fd; > > > > if (dev->mem && !vhost_memory_changed(&memory, dev->mem)) > { > > @@ -714,8 +715,9 @@ vhost_user_set_mem_table(struct virtio_net *dev, > struct VhostUserMsg *pmsg) > > } > > mmap_size = RTE_ALIGN_CEIL(mmap_size, alignment); > > > > + populate = (dev->dequeue_zero_copy) ? MAP_POPULATE : > 0; > > mmap_addr = mmap(NULL, mmap_size, PROT_READ | > PROT_WRITE, > > - MAP_SHARED | MAP_POPULATE, fd, 0); > > + MAP_SHARED | populate, fd, 0); > > > > if (mmap_addr == MAP_FAILED) { > > RTE_LOG(ERR, VHOST_CONFIG, > > > > Wouldn't not populating all the guest memory have a bad impact on 0% > acceptable loss use-cases?
Yes, it could affect such use case; but we can address that by warming up the system a little bit, can't we? From a good point of view, it could save the memory for VMs without pre-allocating. Thanks, Jianfeng
