[PATCH -mm 0/2] mm: page_ext: split page_ext flags

Yafang Shao
2022-12-17T10:58:57Z

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(-)

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2.30.1 (Apple Git-130)