search for: arch_free_pag

On 06/29/2018 03:46 PM, David Hildenbrand wrote: >> >> I'm afraid it can't. For example, when we have a guest booted, without >> too many memory activities. Assume the guest has 8GB free memory. The >> arch_free_page there won't be able to capture the 8GB free pages since >> there is no free() called. This results in no free pages reported to host. > > So, it takes some time from when the guest boots up until the balloon > device was initialized and therefore page hinting can start. For that...

On 06/29/2018 03:46 PM, David Hildenbrand wrote: >> >> I'm afraid it can't. For example, when we have a guest booted, without >> too many memory activities. Assume the guest has 8GB free memory. The >> arch_free_page there won't be able to capture the 8GB free pages since >> there is no free() called. This results in no free pages reported to host. > > So, it takes some time from when the guest boots up until the balloon > device was initialized and therefore page hinting can start. For that...

...EMU will not hotplug memory during migration". This > does not feel like a clean solution. > > I am still not sure if we really need this interface, especially as real > free page hinting might be on its way. > > a) we perform free page hinting by setting all free pages > (arch_free_page()) to zero. Migration will detect zero pages and > minimize #pages to migrate. I don't think this is a good idea but Michel > suggested to do a performance evaluation and Nitesh is looking into that > right now. The hypervisor doesn't get the zero pages for free. It pays lots of...

...EMU will not hotplug memory during migration". This > does not feel like a clean solution. > > I am still not sure if we really need this interface, especially as real > free page hinting might be on its way. > > a) we perform free page hinting by setting all free pages > (arch_free_page()) to zero. Migration will detect zero pages and > minimize #pages to migrate. I don't think this is a good idea but Michel > suggested to do a performance evaluation and Nitesh is looking into that > right now. The hypervisor doesn't get the zero pages for free. It pays lots of...

On 29.06.2018 13:31, Wei Wang wrote: > On 06/29/2018 03:46 PM, David Hildenbrand wrote: >>> >>> I'm afraid it can't. For example, when we have a guest booted, without >>> too many memory activities. Assume the guest has 8GB free memory. The >>> arch_free_page there won't be able to capture the 8GB free pages since >>> there is no free() called. This results in no free pages reported to host. >> >> So, it takes some time from when the guest boots up until the balloon >> device was initialized and therefore page hinting can...

...se pages, >> right? As soon as the spinlock is released, someone can allocate a >> page, and put good data in it. What keeps the hypervisor from >> throwing >> away good data? > > That looks like it may be the wrong API, then? > > We already have hooks called arch_free_page and > arch_alloc_page in the VM, which are called when > pages are freed, and allocated, respectively. > > Nitesh Lal (on the CC list) is working on a way > to efficiently batch recently freed pages for > free page hinting to the hypervisor. > > If that is done efficientl...

...se pages, >> right? As soon as the spinlock is released, someone can allocate a >> page, and put good data in it. What keeps the hypervisor from >> throwing >> away good data? > > That looks like it may be the wrong API, then? > > We already have hooks called arch_free_page and > arch_alloc_page in the VM, which are called when > pages are freed, and allocated, respectively. > > Nitesh Lal (on the CC list) is working on a way > to efficiently batch recently freed pages for > free page hinting to the hypervisor. > > If that is done efficientl...

...31, Wei Wang wrote: > > On 06/29/2018 03:46 PM, David Hildenbrand wrote: > >>> > >>> I'm afraid it can't. For example, when we have a guest booted, > >>> without too many memory activities. Assume the guest has 8GB free > >>> memory. The arch_free_page there won't be able to capture the 8GB > >>> free pages since there is no free() called. This results in no free pages > reported to host. > >> > >> So, it takes some time from when the guest boots up until the balloon > >> device was initialized and t...

...during migration". This >> does not feel like a clean solution. >> >> I am still not sure if we really need this interface, especially as real >> free page hinting might be on its way. >> >> a) we perform free page hinting by setting all free pages >> (arch_free_page()) to zero. Migration will detect zero pages and >> minimize #pages to migrate. I don't think this is a good idea but Michel >> suggested to do a performance evaluation and Nitesh is looking into that >> right now. > > The hypervisor doesn't get the zero pages for...

...free page hinting would be the optimum solution, > > if > > done right. This would avoid the batch interface and even turn > > virtio-balloon in some sense useless. > > I agree with that. Let me go into some more detail of > what Nitesh is implementing: > > 1) In arch_free_page, the being-freed page is added > to a per-cpu set of freed pages. > 2) Once that set is full, arch_free_pages goes into a > slow path, which: > 2a) Iterates over the set of freed pages, and > 2b) Checks whether they are still free, and > 2c) Adds the still free pag...

...free page hinting would be the optimum solution, > > if > > done right. This would avoid the batch interface and even turn > > virtio-balloon in some sense useless. > > I agree with that. Let me go into some more detail of > what Nitesh is implementing: > > 1) In arch_free_page, the being-freed page is added > to a per-cpu set of freed pages. > 2) Once that set is full, arch_free_pages goes into a > slow path, which: > 2a) Iterates over the set of freed pages, and > 2b) Checks whether they are still free, and > 2c) Adds the still free pag...

...e content and provide a fresh frame containing zeroes instead. To communicate the page states "unused" and "stable" to the host two architecture defined primitives page_set_unused() and page_set_stable() are introduced, which are used in the page allocator. The already existing arch_free_page is not used for page_set_unused since it is called before the reserved pages check. In addition arch_free_page can do anything on a given architecture, while page_set_stable() and page_set_unused() have a clearly defined meaning. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --...

...e content and provide a fresh frame containing zeroes instead. To communicate the page states "unused" and "stable" to the host two architecture defined primitives page_set_unused() and page_set_stable() are introduced, which are used in the page allocator. The already existing arch_free_page is not used for page_set_unused since it is called before the reserved pages check. In addition arch_free_page can do anything on a given architecture, while page_set_stable() and page_set_unused() have a clearly defined meaning. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --...

...incoming: > > No, I think proper free page hinting would be the optimum solution, > if > done right. This would avoid the batch interface and even turn > virtio-balloon in some sense useless. I agree with that. Let me go into some more detail of what Nitesh is implementing: 1) In arch_free_page, the being-freed page is added to a per-cpu set of freed pages. 2) Once that set is full, arch_free_pages goes into a slow path, which: 2a) Iterates over the set of freed pages, and 2b) Checks whether they are still free, and 2c) Adds the still free pages to a list that is to...

...U will not hotplug memory during migration". This > does not feel like a clean solution. > > I am still not sure if we really need this interface, especially as real > free page hinting might be on its way. > > a) we perform free page hinting by setting all free pages > (arch_free_page()) to zero. Migration will detect zero pages and > minimize #pages to migrate. I don't think this is a good idea but Michel > suggested to do a performance evaluation and Nitesh is looking into that > right now. Yes this test is needed I think. If we can get most of the benefit witho...

...U will not hotplug memory during migration". This > does not feel like a clean solution. > > I am still not sure if we really need this interface, especially as real > free page hinting might be on its way. > > a) we perform free page hinting by setting all free pages > (arch_free_page()) to zero. Migration will detect zero pages and > minimize #pages to migrate. I don't think this is a good idea but Michel > suggested to do a performance evaluation and Nitesh is looking into that > right now. Yes this test is needed I think. If we can get most of the benefit witho...

...released, someone can allocate a >>>> page, and put good data in it. What keeps the hypervisor from >>>> throwing >>>> away good data? >>> >>> That looks like it may be the wrong API, then? >>> >>> We already have hooks called arch_free_page and >>> arch_alloc_page in the VM, which are called when >>> pages are freed, and allocated, respectively. >>> >>> Nitesh Lal (on the CC list) is working on a way >>> to efficiently batch recently freed pages for >>> free page hinting to the hy...

...released, someone can allocate a >>>> page, and put good data in it. What keeps the hypervisor from >>>> throwing >>>> away good data? >>> >>> That looks like it may be the wrong API, then? >>> >>> We already have hooks called arch_free_page and >>> arch_alloc_page in the VM, which are called when >>> pages are freed, and allocated, respectively. >>> >>> Nitesh Lal (on the CC list) is working on a way >>> to efficiently batch recently freed pages for >>> free page hinting to the hy...

Please stop cc'ing me on things also sent to closed mailing lists (virtio-dev at lists.oasis-open.org). I'm happy to review things on open lists, but I'm not fond of the closed lists bouncing things at me. On 06/09/2017 03:41 AM, Wei Wang wrote: > Add a function to find a page block on the free list specified by the > caller. Pages from the page block may be used immediately

Please stop cc'ing me on things also sent to closed mailing lists (virtio-dev at lists.oasis-open.org). I'm happy to review things on open lists, but I'm not fond of the closed lists bouncing things at me. On 06/09/2017 03:41 AM, Wei Wang wrote: > Add a function to find a page block on the free list specified by the > caller. Pages from the page block may be used immediately