Hi,
On 3/26/19 2:00 AM, Lu, Wenzhuo wrote:
Hi Maxime,
-----Original Message-----
From: Maxime Coquelin [mailto:maxime.coque...@redhat.com]
Sent: Monday, March 25, 2019 4:26 PM
To: Lu, Wenzhuo <wenzhuo...@intel.com>; dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v5 6/8] net/ice: support Rx AVX2 vector
Hi,
On 3/25/19 3:22 AM, Lu, Wenzhuo wrote:
Hi Maxime,
-----Original Message-----
From: Maxime Coquelin [mailto:maxime.coque...@redhat.com]
Sent: Friday, March 22, 2019 6:12 PM
To: Lu, Wenzhuo <wenzhuo...@intel.com>; dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v5 6/8] net/ice: support Rx AVX2
vector
+#ifndef RTE_LIBRTE_ICE_16BYTE_RX_DESC
I see same is done for other Intel NICs, but I wonder what would be
the performance cost of making it dynamic, if any cost?
Currently we don't have a good idea to make it dynamic. If we use pointer
to point to different functions for 16 byte and 32 byte, there's too much
duplicate code to make it hard to maintain. If we use the same function, and
check the configure in it. It impacts the performance.
Have you done some measurements, what would be the performance
impact?
I mean if we check the configuration is 16 byte or 32 byte, this check will
consume extra CPU cycles.
That why I think the better way is to have different paths for 16 byte and 32
byte. We should choose the appropriate path at the beginning.
As HW does not support to change the configuration dynamically. The
device must be stopped and restarted if the configuration is changed. It's not
very helpful to make it a dynamic configuration. We assume that the users
can make their choice at the beginning and will not change it.
The problem is that the user has to recompile to switch between the two
configurations. And it may not be an option for the user if he uses dpdk
packaged by a distribution, for example.
Maybe I was not clear, but I don't mean to be able to switch mode while the
port is started. I think it would be better to make it possible to switch mode
at application startup time.
Yes, I understand the problem is the recompiling. But we think the users will
not change it after they made decision. That's why's acceptable in previous
drivers.
The problem is that the user may not be able to change it, if he does
not get DPDK from source but from a distribution like Debian, Ubuntu or
Red Hat.
In this case, it means the user has no choice than sticking to 32 bytes
descriptors.
Agree it's better to remove all the compile configuration. Looks like that's
what we're trying to do. We'd like to think about how to optimize it later.
My suggestion would be a devarg, so that you can have a per-port
policy (which is another advantage of doing so).
Having it dynamic (as a dev arg for instance) would make it possible
to change the value when the user is using dpdk from a distro. It
would also help testing coverage.
Btw, how do you select this option with meson build system?
Not very familiar with meson. As I know, we can change the meson.build
to add the configure.
Ok, then please try to do it, because the legacy build system is going to be
deprecated.
