On 7/22/2015 7:46 PM, Christoph Hellwig wrote:
Just curious: what's the tradeoff between allocating the page list
in the core vs duplicating it in all the drivers? Does the driver
variant give us any benefits?
It's not necessarily a page list... (i.e. a real scatterlist).
I it will make more sense in patch 41/43.
Moreover, as I wrote in the cover-letter. I noticed that several
drivers keep shadows anyway for various reasons. For example mlx4
sets the page list with a preset-bit (related to ODP...) so at
registration time we see the loop:
for (i = 0; i < mr->npages; ++i)
mr->mpl[i] = cpu_to_be64(mr->pl[i] | MLX4_MTT_FLAG_PRESENT);
Given that this not a single example, I'd expect drivers to skip this
duplication (hopefully).
Sagi.
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