Re: [PATCH v1 0/3] Virtio-balloon Improvement
On 10/22/2017 11:19 AM, Michael S. Tsirkin wrote: On Fri, Oct 20, 2017 at 07:54:23PM +0800, Wei Wang wrote: This patch series intends to summarize the recent contributions made by Michael S. Tsirkin, Tetsuo Handa, Michal Hocko etc. via reporting and discussing the related deadlock issues on the mailinglist. Please check each patch for details. >From a high-level point of view, this patch series achieves: 1) eliminate the deadlock issue fundamentally caused by the inability to run leak_balloon and fill_balloon concurrently; We need to think about this carefully. Is it an issue that leak can now bypass fill? It seems that we can now try to leak a page before fill was seen by host, but I did not look into it deeply. I really like my patch for this better at least for current kernel. I agree we need to work more on 2+3. Since we have many customers interested in the "Virtio-balloon Enhancement" series, please review the v17 patches first (it has a dependency on your patch for that deadlock fix, so I included it there too), and we can get back to 2+3 here after that series is done. Thanks. Best, Wei ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v1 0/3] Virtio-balloon Improvement
On 10/22/2017 11:19 AM, Michael S. Tsirkin wrote: On Fri, Oct 20, 2017 at 07:54:23PM +0800, Wei Wang wrote: This patch series intends to summarize the recent contributions made by Michael S. Tsirkin, Tetsuo Handa, Michal Hocko etc. via reporting and discussing the related deadlock issues on the mailinglist. Please check each patch for details. >From a high-level point of view, this patch series achieves: 1) eliminate the deadlock issue fundamentally caused by the inability to run leak_balloon and fill_balloon concurrently; We need to think about this carefully. Is it an issue that leak can now bypass fill? It seems that we can now try to leak a page before fill was seen by host, but I did not look into it deeply. I really like my patch for this better at least for current kernel. I agree we need to work more on 2+3. Yes, we can check more. But from the original intention: (copied from the commit e22504296d) balloon_lock (mutex) : synchronizes the access demand to elements of struct virtio_balloon and its queue operations; This implementation has covered what balloon_lock achieves. We have inflating and deflating decoupled and use a small lock for each vq respectively. I also tested inflating 20G, and before it's done, requested to deflating 20G, all work fine. 2) enable OOM to release more than 256 inflated pages; and Does just this help enough? How about my patch + 2? Tetsuo, what do you think? 3) stop inflating when the guest is under severe memory pressure (i.e. OOM). But when do we finally inflate? Question is how does host know it needs to resend an interrupt, and when should it do it? I think "when to inflate again" should be a policy defined by the orchestration layer software on the host. A reasonable inflating request should be sent to a guest on the condition that this guest has enough free memory to inflate (virtio-balloon memory stats has already supported to report that info). If the policy defines to inflate guest memory without considering whether the guest is even under memory pressure. The mechanism we provide here is to offer no pages to the host in that case. I think this should be reasonable. Best, Wei ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
Re: [PATCH v1 0/3] Virtio-balloon Improvement
On Fri, Oct 20, 2017 at 07:54:23PM +0800, Wei Wang wrote: > This patch series intends to summarize the recent contributions made by > Michael S. Tsirkin, Tetsuo Handa, Michal Hocko etc. via reporting and > discussing the related deadlock issues on the mailinglist. Please check > each patch for details. > > >From a high-level point of view, this patch series achieves: > 1) eliminate the deadlock issue fundamentally caused by the inability > to run leak_balloon and fill_balloon concurrently; We need to think about this carefully. Is it an issue that leak can now bypass fill? It seems that we can now try to leak a page before fill was seen by host, but I did not look into it deeply. I really like my patch for this better at least for current kernel. I agree we need to work more on 2+3. > 2) enable OOM to release more than 256 inflated pages; and Does just this help enough? How about my patch + 2? Tetsuo, what do you think? > 3) stop inflating when the guest is under severe memory pressure > (i.e. OOM). But when do we finally inflate? Question is how does host know it needs to resend an interrupt, and when should it do it? > Here is an example of the benefit brought by this patch series: > The guest sets virtio_balloon.oom_pages=10. When the host requests > to inflate 7.9G of an 8G idle guest, the guest can still run normally > since OOM can guarantee at least 10 pages (400MB) for the guest. > Without the above patches, the guest will kill all the killable > processes and fall into kernel panic finally. > > Wei Wang (3): > virtio-balloon: replace the coarse-grained balloon_lock > virtio-balloon: deflate up to oom_pages on OOM > virtio-balloon: stop inflating when OOM occurs > > drivers/virtio/virtio_balloon.c | 149 > > 1 file changed, 91 insertions(+), 58 deletions(-) > > -- > 2.7.4 ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
[PATCH v1 0/3] Virtio-balloon Improvement
This patch series intends to summarize the recent contributions made by Michael S. Tsirkin, Tetsuo Handa, Michal Hocko etc. via reporting and discussing the related deadlock issues on the mailinglist. Please check each patch for details. >From a high-level point of view, this patch series achieves: 1) eliminate the deadlock issue fundamentally caused by the inability to run leak_balloon and fill_balloon concurrently; 2) enable OOM to release more than 256 inflated pages; and 3) stop inflating when the guest is under severe memory pressure (i.e. OOM). Here is an example of the benefit brought by this patch series: The guest sets virtio_balloon.oom_pages=10. When the host requests to inflate 7.9G of an 8G idle guest, the guest can still run normally since OOM can guarantee at least 10 pages (400MB) for the guest. Without the above patches, the guest will kill all the killable processes and fall into kernel panic finally. Wei Wang (3): virtio-balloon: replace the coarse-grained balloon_lock virtio-balloon: deflate up to oom_pages on OOM virtio-balloon: stop inflating when OOM occurs drivers/virtio/virtio_balloon.c | 149 1 file changed, 91 insertions(+), 58 deletions(-) -- 2.7.4 ___ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
