From: Jason Gunthorpe <jgg@ziepe.ca>
To: Liran Alon <liran.alon@oracle.com>
Cc: "Will Deacon" <will@kernel.org>,
saeedm@mellanox.com, leon@kernel.org, netdev@vger.kernel.org,
linux-rdma@vger.kernel.org, eli@mellanox.com,
tariqt@mellanox.com, danielm@mellanox.com,
"Håkon Bugge" <haakon.bugge@oracle.com>
Subject: Re: [PATCH] net: mlx5: Use writeX() to ring doorbell and remove reduntant wmb()
Date: Fri, 3 Jan 2020 15:06:39 -0400 [thread overview]
Message-ID: <20200103190639.GD9706@ziepe.ca> (raw)
In-Reply-To: <1C8D5596-F9AD-4E9F-B462-D63DCEEFFE54@oracle.com>
On Fri, Jan 03, 2020 at 08:38:51PM +0200, Liran Alon wrote:
> Actually after re-reading AMD Optimization Guide SDM, I see it is
> guaranteed that: “Write-combining is closed if all 64 bytes of the
> write buffer are valid”. And this is indeed always the case for AWS
> ENA LLQ. Because as can be seen at ena_com_config_llq_info(),
> desc_list_entry_size is either 128, 192 or 256. i.e. Always a
> multiple of 64 bytes. So this explains why this wasn’t an issue in
> production.
That makes a lot of sense
So, the problem with defining WC in the kernel memory model still
remains, but it is back to a theoretical one.
Jason
prev parent reply other threads:[~2020-01-03 19:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-02 17:44 [PATCH] net: mlx5: Use writeX() to ring doorbell and remove reduntant wmb() Liran Alon
2020-01-02 19:29 ` Jason Gunthorpe
2020-01-02 19:45 ` Liran Alon
2020-01-02 20:58 ` Jason Gunthorpe
2020-01-02 22:21 ` Liran Alon
2020-01-03 13:37 ` Jason Gunthorpe
2020-01-03 16:31 ` Liran Alon
2020-01-03 16:36 ` Jason Gunthorpe
2020-01-03 16:42 ` Liran Alon
2020-01-03 18:38 ` Liran Alon
2020-01-03 19:06 ` Jason Gunthorpe [this message]
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