Messages in this thread | | | Date | Mon, 06 Oct 2014 07:07:37 -0700 | From | Laura Abbott <> | Subject | Re: [PATCH 1/1] [ion]: system-heap use PAGE_ALLOC_COSTLY_ORDER for high order |
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On 10/6/2014 3:27 AM, Heesub Shin wrote: > Hello Kumar, > > On 10/06/2014 05:31 PM, Pintu Kumar wrote: >> The Android ion_system_heap uses allocation fallback mechanism >> based on 8,4,0 order pages available in the system. >> It changes gfp flags based on higher order allocation request. >> This higher order value is hard-coded as 4, instead of using >> the system defined higher order value. >> Thus replacing this hard-coded value with PAGE_ALLOC_COSTLY_ORDER >> which is defined as 3. >> This will help mapping the higher order request in system heap with >> the actual allocation request. > > Quite reasonable. > > Reviewed-by: Heesub Shin <heesub.shin@samsung.com> > > BTW, Anyone knows how the allocation order (8,4 and 0) was decided? I > think only Google guys might know the answer. > > regards, > heesub >
My understanding was this was completely unrelated to the costly order and was related to the page sizes corresponding to IOMMU page sizes (1MB, 64K, 4K). This won't make a difference for the uncached page pool case but for the not page pool case, I'm not sure if there would be a benefit for trying to get 32K pages with some effort vs. just going back to 4K pages.
Do you have any data/metrics that show a benefit from this patch?
Thanks, Laura
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