Re: [RFC] Lock free fd lookup

From: William Lee Irwin III
Date: Sat Jul 17 2004 - 04:31:44 EST

At some point in the past, Keith Owens wrote:
>>> It requires type stable storage. That is, once a data area has been
>>> allocated to a particular structure type, it always contains that
>>> structure type, even when it has been freed from the list. Each list
>>> requires its own free pool, which can never be returned to the OS.

wli wrote
>>The last of these is particularly lethal.

On Sat, Jul 17, 2004 at 10:50:48AM +0200, Manfred Spraul wrote:
> It might be possible to combine such a lock free algorithms with RCU and
> then set Hugh's SLAB_DESTROY_BY_RCU: It inserts a call_rcu between
> leaving the free pool and returning the page to the OS.

At least I would prefer such a hybrid algorithm if things of this kind
were used in the kernel. From the looks of it, in such algorithms the
structure is still valid for checking of tickets after a voluntary
preemption, in this RCU hybrid not.

-- wli
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