Jan Kiszka <jan.kis...@siemens.com> writes: > On 2012-09-28 14:33, Anthony Liguori wrote: >> Jan Kiszka <jan.kis...@siemens.com> writes: >> >>> On 2012-09-28 01:21, Satoru Moriya wrote: >>>> This is a first time for me to post a patch to qemu-devel. >>>> If there is something missing/wrong, please let me know. >>>> >>>> We have some plans to migrate old enterprise systems which require >>>> low latency (msec order) to kvm virtualized environment. Usually, >>>> we uses mlock to preallocate and pin down process memory in order >>>> to avoid page allocation in latency critical path. On the other >>>> hand, in kvm environment, mlocking in guests is not effective >>>> because it can't avoid page reclaim in host. Actually, to avoid >>>> guest memory reclaim, qemu has "mem-path" option that is actually >>>> for using hugepage. But a memory region of qemu is not allocated >>>> on hugepage, so it may be reclaimed. That may cause a latency >>>> problem. >>>> >>>> To avoid guest and qemu memory reclaim, this patch introduces >>>> a new "mlock" option. With this option, we can preallocate and >>>> pin down guest and qemu memory before booting guest OS. >>> >>> I guess this reduces the likeliness of multi-millisecond latencies for >>> you but not eliminate them. Of course, mlockall is part of our local >>> changes for real-time QEMU/KVM, but it is just one of the many pieces >>> required. I'm wondering how the situation is on your side. >>> >>> I think mlockall should once be enabled automatically as soon as you ask >>> for real-time support for QEMU guests. How that should be controlled is >>> another question. I'm currently carrying a top-level switch "-rt >>> maxprio=x[,policy=y]" here, likely not the final solution. I'm not >>> really convinced we need to control memory locking separately. And as we >>> are very reluctant to add new top-level switches, this is even more >>> important. >> >> I think you're right here although I'd suggest not abbreviating. > > You mean the sense of "-realtime" instead of "-rt"?
Yes. Or any other word that makes sense. Regards, Anthony Liguori > > Jan > > -- > Siemens AG, Corporate Technology, CT RTC ITP SDP-DE > Corporate Competence Center Embedded Linux
