Re: [PATCH v3 net-next 08/14] mlx4: use order-0 pages for RX

From: Tom Herbert <redacted>
Date: Thu, 16 Feb 2017 09:05:26 -0800

On Thu, Feb 16, 2017 at 5:08 AM, Tariq Toukan [off-list ref] wrote:

quoted

On 15/02/2017 6:57 PM, Eric Dumazet wrote:

quoted

On Wed, Feb 15, 2017 at 8:42 AM, Tariq Toukan [off-list ref] wrote:

quoted

Isn't it the same principle in page_frag_alloc() ?
It is called form __netdev_alloc_skb()/__napi_alloc_skb().

Why is it ok to have order-3 pages (PAGE_FRAG_CACHE_MAX_ORDER) there?

This is not ok.

This is a very well known problem, we already mentioned that here in the
past,
but at least core networking stack uses  order-0 pages on PowerPC.

You're right, we should have done this as well in mlx4 on PPC.

quoted

mlx4 driver suffers from this problem 100% more than other drivers ;)

One problem at a time Tariq. Right now, only mlx4 has this big problem
compared to other NIC.

We _do_ agree that the series improves the driver's quality, stability,
and performance in a fragmented system.

But due to the late rc we're in, and the fact that we know what benchmarks
our customers are going to run, we cannot Ack the series and get it
as is inside kernel 4.11.

You're admitting that Eric's patches improve driver quality,
stability, and performance but you're not allowing this in the kernel
because "we know what benchmarks our customers are going to run".
Sorry, but that is a weak explanation.

I have to agree with Tom and Eric.

If your customers have gotten into the habit of using metrics which
actually do not represent real life performance, that is a completely
inappropriate reason to not include Eric's changes as-is.