> From: Nitin Gupta [mailto:ngupta@xxxxxxxxxx] > > Nitin, can zsmalloc allow full page allocation by assigning > > an actual physical pageframe (which is what zram does now)? > > Or will it allocate PAGE_SIZE bytes which zsmalloc will allocate > > crossing a page boundary which, presumably, will have much worse > > impact on page allocator availability when these pages are > > "reclaimed" via your swap notify callback. > > zsmalloc does not add any object headers, so when allocating PAGE_SIZE > you get a separate page from as if you did alloc_page(). So, it does not > span page boundaries. > > > Though this may be rare across all workloads, it may turn out > > to be very common for certain workloads (e.g. if the workload > > has many dirty anonymous pages that are already compressed > > by userland). > > > > It may not be worth cleaning up the code if it causes > > performance issues with this case. > > > > And anyway can zsmalloc handle and identify to the caller pages > > that are both compressed and "native" (uncompressed)? It > > certainly has to handle both if you remove ZRAM_UNCOMPRESSED > > as compressing some pages actually results in more than > > PAGE_SIZE bytes. So you need to record somewhere that > > this "compressed page" is special and that must somehow > > be communicated to the caller of your "get" routine. > > > > (Just trying to save Minchan from removing all that code but > > then needing to add it back again.) > > zsmalloc cannot identify compressed vs uncompressed pages. However, in > zram, we can tell if the page is uncompressed using table[i]->size which > is set to PAGE_SIZE for uncompressed pages. Pages that compress to > more than PAGE_SIZE (i.e. expand on compression) are stored > as-is/uncompressed and thus will have size field set to PAGE_SIZE. > > Thus, we do not require ZRAM_UNCOMPRESSED flag when using zsmalloc for > both compressed and uncompressed pages. Good to know. Nice work in zsmalloc and zram! Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href