Re: [PATCH 1/1] network memory allocator.

From: Rick Jones
Date: Mon Aug 14 2006 - 13:40:38 EST

Evgeniy Polyakov wrote:
On Mon, Aug 14, 2006 at 10:07:48PM +1000, Keith Owens (kaos@xxxxxxxxxx) wrote:

Evgeniy Polyakov (on Mon, 14 Aug 2006 15:04:03 +0400) wrote:

Network tree allocator can be used to allocate memory for all network
operations from any context....
Design of allocator allows to map all node's pages into userspace thus
allows to have true zero-copy support for both sending and receiving

Is that true for architectures with virtually indexed caches? How do
you avoid the cache aliasing problems?

Pages are preallocated and stolen from main memory allocator, what is
the problem with that caches? Userspace can provide enough offset so
that pages would not create aliases - it is usuall mmap.

That may depend heavily on the architecture. PA-RISC has the concept of spaceid's, and bits from the spaceid can be included in the hash along with bits from the offset. So, it is not possible to simply match the offset, one has to make sure that hash bits from the spaceid hash the same as well.

Now, PA-RISC CPUs have the ability to disable spaceid hashing, and it is entirely possible that the PA-RISC linux port does that, but I thought I would mention it as an example. I'm sure the "official" PA-RISC linux folks can expand on that much much better than I can.

rick jones
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