linux-kernel - [PATCH 0/1] mm/page_ext: remove unnecessary stack

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Date:	Tue, 27 Jan 2015 00:52:11 +0300
From:	Sergei Rogachev <rogachevsergei@...il.com>
To:	akpm@...ux-foundation.org, iamjoonsoo.kim@....com
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Sergei Rogachev <rogachevsergei@...il.com>
Subject: [PATCH 0/1] mm/page_ext: remove unnecessary stack_trace field

The functionality named "page owner" has resurrected the structure page_ext
which is used for keeping additional page-related information. Every page in
the system has its own corresponding page_ext structure.

Page owner uses this structure to keep allocation order, gfp_mask and backtrace
entries; moreover page_ext includes a field of type "struct stack_trace". And
this field is used for collecting backtraces: a pointer to struct stack_trace is
passed to save_stack_trace in the function __set_page_owner. But it is really
not necessary to keep dedicated stack_trace structures for all physical pages in
the system, only an amount of saved backtrace entries is needed to be saved.

The stack_trace structure can be allocated on the stack (it is relatively small)
and used for save_stack_trace invocation. Such change can save 12 bytes of
memory per page if page owner functionality is enabled.

Sergei Rogachev (1):
  mm/page_ext: remove unnecessary stack_trace field

 include/linux/page_ext.h |  2 +-
 mm/page_owner.c          | 21 ++++++++++++---------
 2 files changed, 13 insertions(+), 10 deletions(-)

-- 
1.9.1

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