diff options
author | Hugh Dickins <hugh@veritas.com> | 2007-06-27 14:09:53 -0700 |
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committer | Willy Tarreau <w@1wt.eu> | 2007-08-15 10:02:33 +0200 |
commit | 356177f4dac83a81bee944b8776709bb6b62a338 (patch) | |
tree | 739f309bf0ff6530a21346c89834d76dc2cd5f1d /drivers | |
parent | 0c53130a7d5da7597548f885e7b3238af18945d3 (diff) |
[PATCH] mm: kill validate_anon_vma to avoid mapcount BUG
validate_anon_vma gave a useful check on the integrity of the anon_vma list
when Andrea was developing obj rmap; but it was not enabled in SLES9
itself, nor in mainline, until Nick changed commented-out RMAP_DEBUG to
configurable CONFIG_DEBUG_VM in 2.6.17. Now Petr Vandrovec reports that
its BUG_ON(mapcount > 100000) can easily crash a CONFIG_DEBUG_VM=y system.
That limit was just an arbitrary number to protect against an infinite
loop. We could raise it to something enormous (depending on sizeof struct
vma and size of memory?); but I rather think validate_anon_vma has outlived
its usefulness, and is better just removed - which gives a magnificent
performance boost to anything like Petr's test program ;)
Of course, a very long anon_vma list is bad news for preemption latency,
and I believe there has been one recent report of such: let's not forget
that, but validate_anon_vma only makes it worse not better.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Petr Vandrovec <petr@vmware.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
0 files changed, 0 insertions, 0 deletions