search for: arch_alloc_page

...? 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 efficiently enough (eg. with > MA...

...? 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 efficiently enough (eg. with > MA...

...on works, there are many many things we need to consider when pages > > > are allocated to users. > > > For example, we need to take care of the nr_free > > > counter, we need to check the watermark and perform the related actions. > > > Also the folks working on arch_alloc_page to monitor page allocation > > > activities would get a surprise..if page allocation is allowed to work in > > > this way. > > > > > mm/ code is well positioned to handle all this correctly. > > I'm afraid that would be a re-implementation of the alloc f...

...on works, there are many many things we need to consider when pages > > > are allocated to users. > > > For example, we need to take care of the nr_free > > > counter, we need to check the watermark and perform the related actions. > > > Also the folks working on arch_alloc_page to monitor page allocation > > > activities would get a surprise..if page allocation is allowed to work in > > > this way. > > > > > mm/ code is well positioned to handle all this correctly. > > I'm afraid that would be a re-implementation of the alloc f...

...need to consider when pages > > > > > are allocated to users. > > > > > For example, we need to take care of the nr_free > > > > > counter, we need to check the watermark and perform the related actions. > > > > > Also the folks working on arch_alloc_page to monitor page allocation > > > > > activities would get a surprise..if page allocation is allowed to work in > > > > > this way. > > > > > > > > > mm/ code is well positioned to handle all this correctly. > > > I'm afraid that...

...need to consider when pages > > > > > are allocated to users. > > > > > For example, we need to take care of the nr_free > > > > > counter, we need to check the watermark and perform the related actions. > > > > > Also the folks working on arch_alloc_page to monitor page allocation > > > > > activities would get a surprise..if page allocation is allowed to work in > > > > > this way. > > > > > > > > > mm/ code is well positioned to handle all this correctly. > > > I'm afraid that...

...low 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 be passed to the hypervisor, to be MADV_FREEd. > 2d) Makes that hypercall. > > Meanwhile all arch_alloc_pages has to do is make sure it > does not allocate a page while it is currently being > MADV_FREEd on the hypervisor side. > > The code Wei is working on looks like it could be > suitable for steps (2c) and (2d) above. Nitesh already > has code for steps 1 through 2b. > > --...

...low 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 be passed to the hypervisor, to be MADV_FREEd. > 2d) Makes that hypercall. > > Meanwhile all arch_alloc_pages has to do is make sure it > does not allocate a page while it is currently being > MADV_FREEd on the hypervisor side. > > The code Wei is working on looks like it could be > suitable for steps (2c) and (2d) above. Nitesh already > has code for steps 1 through 2b. > > --...

...t; > > > > are allocated to users. > > > > > > > For example, we need to take care of the nr_free > > > > > > > counter, we need to check the watermark and perform the related actions. > > > > > > > Also the folks working on arch_alloc_page to monitor page allocation > > > > > > > activities would get a surprise..if page allocation is allowed to work in > > > > > > > this way. > > > > > > > > > > > > > mm/ code is well positioned to handle all this corre...

...t; > > > > are allocated to users. > > > > > > > For example, we need to take care of the nr_free > > > > > > > counter, we need to check the watermark and perform the related actions. > > > > > > > Also the folks working on arch_alloc_page to monitor page allocation > > > > > > > activities would get a surprise..if page allocation is allowed to work in > > > > > > > this way. > > > > > > > > > > > > > mm/ code is well positioned to handle all this corre...

...f we check how the regular > allocation works, there are many many things we need to consider when pages > are allocated to users. > For example, we need to take care of the nr_free > counter, we need to check the watermark and perform the related actions. > Also the folks working on arch_alloc_page to monitor page allocation > activities would get a surprise..if page allocation is allowed to work in > this way. > mm/ code is well positioned to handle all this correctly. > > > > > > > > + arrays[i] = > > > + (__le64 *)__get_free_pages(__GFP_A...

...f we check how the regular > allocation works, there are many many things we need to consider when pages > are allocated to users. > For example, we need to take care of the nr_free > counter, we need to check the watermark and perform the related actions. > Also the folks working on arch_alloc_page to monitor page allocation > activities would get a surprise..if page allocation is allowed to work in > this way. > mm/ code is well positioned to handle all this correctly. > > > > > > > > + arrays[i] = > > > + (__le64 *)__get_free_pages(__GFP_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. >>> >>&gt...

...>>>> 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. >>> >>&gt...

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

...red > a very special corner case that I would argue is not worth it to be > optimized. > > If I am missing something important here, sorry in advance :) > Probably I didn't explain that well. Please see my re-try: That work is to monitor page allocation and free activities via arch_alloc_pages and arch_free_pages. It has per-CPU lists to record the pages that are freed to the mm free list, and the per-CPU lists dump the recorded pages to a global list when any of them is full. So its own per-CPU list will only be able to get free pages when there is an mm free() function gets called....

...red > a very special corner case that I would argue is not worth it to be > optimized. > > If I am missing something important here, sorry in advance :) > Probably I didn't explain that well. Please see my re-try: That work is to monitor page allocation and free activities via arch_alloc_pages and arch_free_pages. It has per-CPU lists to record the pages that are freed to the mm free list, and the per-CPU lists dump the recorded pages to a global list when any of them is full. So its own per-CPU list will only be able to get free pages when there is an mm free() function gets called....

...e contents of these 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 efficiently enough (eg. with MADV_FREE on the hypervisor side for lazy...

...l, 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 be passed to the hypervisor, to be MADV_FREEd. 2d) Makes that hypercall. Meanwhile all arch_alloc_pages has to do is make sure it does not allocate a page while it is currently being MADV_FREEd on the hypervisor side. The code Wei is working on looks like it could be suitable for steps (2c) and (2d) above. Nitesh already has code for steps 1 through 2b. -- All rights reversed -------------- next...