On Mon, 13 Apr 2020 08:11:59 -0700 Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> wrote: > In addition, unlike madvising the page away there is a pretty > significant performance penalty for having to clear the page a second > time when the page is split or merged. I wonder if there might be an issue with increased memory traffic (and increased energy consumption, etc). If a page is zeroed immediately before getting data written into it (eg, plain old file write(), anonymous pagefault) then we can expect that those 4096 zeroes will be in CPU cache and mostly not written back. But if that page was zeroed a "long" time ago, the caches will probably have been written back. Net result: we go from 4k of memory traffic for a 4k page up to 8k of memory traffic? Also, the name CONFIG_ZERO_PAGE sounds like it has something to do with the long established "zero page". Confusing. CONFIG_PREZERO_PAGE, maybe?
