On 64bit system, page extension is for debugging purpose only currently, because of its overhead, in particular the memory overhead. Once a page_ext is enabled, at least it will take 0.2% of the total memory because of the page_ext flags, no matter this page_ext uses it or not. Currently this page_ext flags is only used for page_owner on 64bit system. So it doesn't make sense to allocate this flags for all page_ext by default. We'd better move it into page_owner's structure, then when someone wants to introduce a new page_ext which may be memory-overhead sensitive, it will save this unneeded overhead. On 32bit system, there's page_idle running on production envrionment, which also uses this page_ext flags. So it will take another 0.2% of total memory if the user enable both page_idle and page_owner after this change, but considering page_owner is for debugging purpose only, the memory overhead in this case won't be a problem. So, let split the page_ext flags. Yafang Shao (2): mm: page_owner: split page_owner's flag from the comm flags mm: page_idle: split 32bit page_idle's flag from the common flags include/linux/page_ext.h | 14 +------------- include/linux/page_idle.h | 39 +++++++++++++++++++++++++++++++++------ mm/page_ext.c | 10 ---------- mm/page_idle.c | 12 ++++++++++++ mm/page_owner.c | 36 ++++++++++++++++++++++-------------- 5 files changed, 68 insertions(+), 43 deletions(-) -- 2.30.1 (Apple Git-130)
