On Sun, 2015-05-31 at 16:47 +0530, Krishna Chaitanya wrote: > > Note # of "messages" as you say is actually irrelevant - you should look > > Well with 138 messages the function and each message 3072 bytes > calls b/w cfg80211 and driver > without the patch: would be 276 calls > with this patch: would be 138 calls > Thats a lot of function calls, don't you think? No, I don't think so. That really should be within the noise, it's all in the icache already after the first round. > > at how often the kernel/user boundary is crossed, that's really far more > > interesting, and your patch makes that MUCH worse when the put size is > > small (say 100 bytes) because then you're practically doing that twice > > as often. > > My patch doesn't deteriorate the situation, and not change the kernel to > user boundary. With/Without the patch 3072 bytes are transported in a > single message from kernel to user. *in your case* In the case that somebody is creating smaller messages it makes things MUCH worse by allowing only half the data to be carried across the kernel/userspace boundary each time any data crosses it, so it will result in many more syscalls in that case. If you're worried about the overhead of a simple function (pointer) call in the kernel, then surely you should be far more worried about this. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
