Messages in this thread | | | Date | Tue, 7 Oct 2008 07:33:46 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 3/3] Convert the UDP hash lock to RCU |
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On Tue, Oct 07, 2008 at 09:16:13AM -0500, Christoph Lameter wrote: > Evgeniy Polyakov wrote: > > On Mon, Oct 06, 2008 at 06:08:09PM -0500, Corey Minyard (minyard@acm.org) wrote: > >> Would using SLAB_DESTROY_BY_RCU be ok, or would that be too expensive? > > > > I tested skb destruction via RCU path, and got 2.5 times worse numbers > > with small-packets-bulk-transfer workload. > > Was this with regular RCU freeing? This will cool down the cacheline before > frees. You need SLAB_DESTROY_BY_RCU to keep the objects cache hot.
Indeed!
But care is required -- SLAB_DESTROY_BY_RCU permits objects to be freed and reallocated while a reader holds a reference. The only guarantee is that the -type- of the data structure will not change while a reader holds a reference. With something like UDP, this might well be sufficient.
Just be careful! ;-)
Thanx, Paul
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