Re: [PATCH 00/16] IB/hfi1: Add a page pinning cache for PSM sdma

On Tue, Mar 08, 2016 at 10:56:48PM +0200, Or Gerlitz wrote:

On Tue, Mar 8, 2016 at 9:14 PM, Dennis Dalessandro
[off-list ref] wrote:

quoted

This patch series adds a performance improvement to user SDMA transfers from
PSM applications by caching user buffer pages after pinning them. Subsequent
uses of the same user buffer will not incur the cost of pinning the same pages
again. Additionally, the cost of unpinning the same pages is avoided.  Buffer
pages are unpinned when the context is torn down or when the driver determines
that the buffer should be evicted from the cache. Cache evictions happen when
there is a request for a new, uncached buffer and the current size of the cache
has reached a pre-defined limit.

If indeed there's a need for such a pin down cache, it should have
been implemented in the IB core, b/c both the problem and the solution
are generic and have nothing to do with certain device driver.

Since this is for psm it has nothing to do with the IB core. I fail to see what that would achieve.

The problem is that you are bypassing the IB core altogether with a
proprietary character device in the hfi1 driver which managed to snick
in even in the presence of reviewer comments during the submission.

Yes there were reviewer comments, and the maintainer made a decision.
I would also not call this proprietary. It is open source after all:

See:  https://github.com/01org/opa-psm2

-Denny
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