On Wednesday 13 December 2017 06:22 PM, Ananyev, Konstantin wrote:
-----Original Message-----
From: Shreyansh Jain [mailto:shreyansh.j...@nxp.com]
Sent: Tuesday, December 12, 2017 1:44 PM
To: Ananyev, Konstantin <konstantin.anan...@intel.com>; Matan Azrad
<ma...@mellanox.com>; Nikhil Agarwal
<nikhil.agar...@linaro.org>
Cc: dev@dpdk.org; Hunt, David <david.h...@intel.com>; nikhil.agar...@nxp.com;
hemant.agra...@nxp.com; Yigit, Ferruh
<ferruh.yi...@intel.com>
Subject: Re: [PATCH 1/3] ethdev: add max burst size to device info
[...]
Doesn't such like devices PMDs should try to retrieve multiple HW burst to
adjust the asked received packet number?
Same thought here...
Can't that limitation be hidden inside PMD by calling HW burst multiple times?
This might be required in some cases for performance.
It is possible that for each request containing N buffers, if the PMD
fetches all N (more than its preferred burst_size), cache misses reduce
the performance - especially for SoC with limited cache size.
Also, a complete cycle of
application->driver->hardware->driver->application can help driver
prefetch buffers - which, in case of hw burst looping, might be too
little to complete the prefetch cycle.
To summarize, indeed this is for performance specific cases and the idea
that @Matan gave for renaming 'perf_buf_size' to highlight this, sounds
logical.
Also if I am not mistaken - it would increase size of struct rte_eth_dev_info,
right?
If so, then it means ABI breakage.
Yes, deprecation notice should have been sent - if we continue with the
dev_info change. To me that looks as one of the option. Maybe, someone
on the list has a better idea.
In theory there is at least 2 free bytes at the end of struct rte_eth_desc_lim.
Might be it would help a bit.
:) Thanks for highlighting.
So, you feel it is OK to reuse this assumption of hole in alignment? It
certainly would bypass the ABI limitation but not sure which cases it
would break (for example, same assumptions by others)
It would an issue in case of 32bit systems, though.
[...]
-
Shreyansh
