Re: [PATCH net-next 09/15] net: increase MAX_SKB_FRAGS

On Thu, Feb 3, 2022 at 11:18 AM Jakub Kicinski [off-list ref] wrote:

On Thu, 3 Feb 2022 09:56:42 -0800 Alexander Duyck wrote:

quoted

quoted

I could make  MAX_SKB_FRAGS a config option, and default to 17, until
all drivers have been fixed.

Alternative is that I remove this patch from the series and we apply
it to Google production kernels,
as we did before.

A config option would probably be preferred. The big issue as I see it
is that changing MAX_SKB_FRAGS is going to have ripples throughout the
ecosystem as the shared info size will be increasing and the queueing
behavior for most drivers will be modified as a result.

I'd vote for making the change and dealing with the fall out. Unlikely
many people would turn this knob otherwise and it's a major difference.
Better not to fork the characteristics of the stack, IMHO.

Another issue with CONFIG_ options is that they are integer.

Trying the following did not work

#define MAX_SKB_FRAGS  ((unsigned long)CONFIG_MAX_SKB_FRAGS)

Because in some places we have

#if    (   MAX_SKB_FRAGS > ...)

(MAX_SKB_FRAGS is UL currently, making it an integer might cause some
signed/unsigned operations buggy)