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Re: rbuf starvation in the iwn driver
On Sun April 11 2010 12:40:45 David Young wrote:
> On Sat, Apr 10, 2010 at 12:49:48PM +1000, matthew green wrote:
> > would you try this variant? it handles the case where MEXTMALLOC()
> > would fail to allocate external storage, and seems to work on my
> > iwn(4). i'll commit this if you confirm it works.
> Is there any reason not to replace the implementation of
> iwn_alloc_rbuf() with MEXTMALLOC(), instead?
I was told there might be a performance hit. My tests with 11g on amd64 are
inconclusive. BTW, it is easy to change the current driver to test this.
I wonder if it would be worth (or even possible) to use pool_cache with the
bus_dmamap allocator. It is pretty simple to add a 4KiB pool to
> Previously, a remote host could exhaust an iwn(4)'s private Rx buffer
> pool by, say, sending a ton of tiny segments to TCP sockets that already
> have a long backlog. Can a remote host now deplete the malloc(9) pool
> in the same way?
That is certainly possible but no different than what is done in other drivers,
e.g. wpi. Look at OpenBSD's MCETGETI for a solution to this problem.
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