Re: [PATCH v2 01/24] mlx4-ib: Use coherent memory for priv pages

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On Jun 15, 2016, at 12:28 AM, Leon Romanovsky <leon@xxxxxxxxxx> wrote:

On Tue, Jun 14, 2016 at 11:15:25PM -0400, Chuck Lever wrote:
From: Sagi Grimberg <sagi@xxxxxxxxxxx>

kmalloc doesn't guarantee the returned memory is all on one page.

IMHO, the patch posted by Christoph at that thread is best way to go,
because you changed streaming DMA mappings to be coherent DMA mappings [1].

"The kernel developers recommend the use of streaming mappings over
coherent mappings whenever possible" [1].

[1] http://www.makelinux.net/ldd3/chp-15-sect-4

Hi Leon-

I'll happily drop this patch from my 4.8 series as soon
as an official mlx4/mlx5 fix is merged.

Meanwhile, I notice some unexplained instability (driver
resets, list corruption, and so on) when I test NFS/RDMA
without this patch included. So it is attached to the
series for anyone with mlx4 who wants to pull my topic
branch and try it out.

hi Chuck,

We plan to send attached patch during our second round of fixes for
mlx4/mlx5 and would be grateful to you if you could provide your
Tested-by tag before.

First of all, IIRC the patch author was Christoph wasn't he.

Plus, you do realize that this patch makes the pages allocation
in granularity of pages. In systems with a large page size this
is completely redundant, it might even be harmful as the storage
ULPs need lots of MRs.

Also, I don't see how that solves the issue, I'm not sure I even
understand the issue. Do you? Were you able to reproduce it?

IFF the pages buffer end not being aligned to a cacheline is problematic
then why not extent it to end in a cacheline? Why in the next full page?
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