diff options
author | Hugh Dickins <hugh@veritas.com> | 2007-06-27 14:09:53 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-06-28 11:34:53 -0700 |
commit | 30acbabae38793c9c9acace4de5b1c1889570768 (patch) | |
tree | c9c1741f04382803475c113865deed065e1ca0cf /drivers/atm/zatm.c | |
parent | 172d0496cd22c98ee2e4238821fa309c01685f3a (diff) | |
download | op-kernel-dev-30acbabae38793c9c9acace4de5b1c1889570768.zip op-kernel-dev-30acbabae38793c9c9acace4de5b1c1889570768.tar.gz |
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>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/atm/zatm.c')
0 files changed, 0 insertions, 0 deletions