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    SubjectRe: [RFC][PATCH 0/1] kmemleak: Fix false positive with alias
    On 18/06/10 08:04 +0200, Doyu Hiroshi (Nokia-D/Helsinki) wrote:
    > 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.

    After comparing the two, my Ack would still strongly be behind the
    first one, the special scan. The additional work over a normal scan
    is limited strictly to those regions that need it, which is a much
    more clinical approach to the problem. Your timing data bears that
    out.

    Phil

    > *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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