> > > > > -----Original Message----- > > > From: Zhao Yan [mailto:yan.y.z...@intel.com] > > > Sent: Thursday, February 21, 2019 10:05 AM > > > To: Gonglei (Arei) <arei.gong...@huawei.com> > > > Cc: alex.william...@redhat.com; qemu-devel@nongnu.org; > > > intel-gvt-...@lists.freedesktop.org; zhengxiao...@alibaba-inc.com; > > > yi.l....@intel.com; eskul...@redhat.com; ziye.y...@intel.com; > > > coh...@redhat.com; shuangtai....@alibaba-inc.com; > dgilb...@redhat.com; > > > zhi.a.w...@intel.com; mlevi...@redhat.com; pa...@linux.ibm.com; > > > a...@ozlabs.ru; eau...@redhat.com; fel...@nutanix.com; > > > jonathan.dav...@nutanix.com; changpeng....@intel.com; > ken....@amd.com; > > > kwankh...@nvidia.com; kevin.t...@intel.com; c...@nvidia.com; > > > k...@vger.kernel.org > > > Subject: Re: [PATCH 0/5] QEMU VFIO live migration > > > > > > > > > > > > > > 5) About log sync, why not register log_global_start/stop in > > > > > vfio_memory_listener? > > > > > > > > > > > > > > > > > seems log_global_start/stop cannot be iterately called in pre-copy > phase? > > > > > for dirty pages in system memory, it's better to transfer dirty data > > > > > iteratively to reduce down time, right? > > > > > > > > > > > > > We just need invoking only once for start and stop logging. Why we need > to > > > call > > > > them literately? See memory_listener of vhost. > > > > > > > the dirty pages in system memory produces by device is incremental. > > > if it can be got iteratively, the dirty pages in stop-and-copy phase can > > > be > > > minimal. > > > :) > > > > > I mean starting or stopping the capability of logging, not log sync. > > > > We register the below callbacks: > > > > .log_sync = vfio_log_sync, > > .log_global_start = vfio_log_global_start, > > .log_global_stop = vfio_log_global_stop, > > > .log_global_start is also a good point to notify logging state. > But if notifying in .save_setup handler, we can do fine-grained > control of when to notify of logging starting together with get_buffer > operation. > Is there any special benifit by registering to .log_global_start/stop? >
Performance benefit when one VM has multiple same vfio devices. Regards, -Gonglei
