linux-kernel - [RFC][PATCH 0/1] kmemleak: Fix false positive with alias

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Date:	Fri, 18 Jun 2010 09:04:14 +0300
From:	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
To:	linux-kernel@...r.kernel.org
Cc:	catalin.marinas@....com, ext-phil.2.carmody@...ia.com,
	linux-omap@...r.kernel.org, Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
Subject: [RFC][PATCH 0/1] kmemleak: Fix false positive with alias

Hi,

This is another version of "kmemleak: Fix false positive", which
introduces another alias tree to keep track of all alias address of
each objects, based on the discussion(*1)

You can also find the previous one(*2), which uses special scan area
for alias addresses with a conversion function.

Compared with both methods, it seems that the current one takes a bit
longer to scan as below, tested with 512 elementes of (*3).

"kmemleak: Fix false positive with alias":
# time echo scan > /mnt/kmemleak
real    0m 8.40s
user    0m 0.00s
sys     0m 8.40s

"kmemleak: Fix false positive with special scan":
# time echo scan > /mnt/kmemleak 
real    0m 3.96s
user    0m 0.00s
sys     0m 3.96s

For our case(*4) to reduce false positives for the 2nd level IOMMU
pagetable allocation, the previous special scan  seems to be enough
lightweight, although there might be possiblity to improve alias
one and also I might misunderstand the original proposal of aliasing.

Any comment would be appreciated.

*1: http://lkml.org/lkml/2010/6/2/282
*2: kmemleak: Fix false positive with special scan
    http://lkml.org/lkml/2010/6/1/137
*3: kmemleak: Add special scan test case
    http://lkml.org/lkml/2010/6/1/134
*4: http://lkml.org/lkml/2010/6/1/136

Hiroshi DOYU (1):
  kmemleak: Fix false positive with alias

 include/linux/kmemleak.h |    4 +
 mm/kmemleak.c            |  198 ++++++++++++++++++++++++++++++++++++++--------
 2 files changed, 168 insertions(+), 34 deletions(-)


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