Ingo Molnar wrote:
* Jeff Garzik <[email protected]> wrote:
* I feel TX NAPI is a useful tool, because it provides an independent TX
process control point and system load feedback point.
Thus I felt this was slightly superior to tasklets.
/me agrees violently
btw., when i played with this tunable under -rt:
enum {
NV_OPTIMIZATION_MODE_THROUGHPUT,
NV_OPTIMIZATION_MODE_CPU
};
static int optimization_mode = NV_OPTIMIZATION_MODE_THROUGHPUT;
the MODE_CPU one gave (much) _higher_ bandwidth. The queueing model in
forcedeth seemed to be not that robust and i think a single queueing
model should be adopted instead of this tunable. (which i think just hid
some bug/dependency) But i never got to the bottom of it so it's just
the impression i got.
That's interesting. It will be informative to narrow down the variables
affected by this. My changes stirred the pot quite a bit :)
* 'throughput' mode enables MSI-X, and separate interrupt vectors for RX
and TX. so, NVIDIA's MSI-X implementation, our generic MSI-X support,
or "Known bugs" (see top of file) may be a factor here.
* 'throughput' mode also changes the NIC's timer interrupt frequency
* do you recall if you were running in NAPI mode? It defaulted to off
in Kconfig, but I turned it on unconditionally.
* I think TX NAPI has the potential to make the optimization_mode
irrelevant (along with the other changes, most notably the interrupt
handling change)
* and overall, yes, if we can have a single queueing model /
optimization mode I am strongly in favor of that.
Testing welcome ;-) Though these patches are raw and "hot off the
presses", so unrelated bugs are practically a certainty. And I am
worrying about the "Known bugs" note at the top. My gut feeling is that
this was, in part, misunderstanding on the part of reverse-engineers,
since corrected when NVIDIA started contributing to the driver.
Jeff
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