netdev - Re: [PATCH net-next-2.6] net: speedup udp receive path

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Message-ID: <1272547307.2222.83.camel@edumazet-laptop>
Date:	Thu, 29 Apr 2010 15:21:47 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	hadi@...erus.ca
Cc:	Changli Gao <xiaosuo@...il.com>,
	David Miller <davem@...emloft.net>, therbert@...gle.com,
	shemminger@...tta.com, netdev@...r.kernel.org,
	Eilon Greenstein <eilong@...adcom.com>,
	Brian Bloniarz <bmb@...enacr.com>
Subject: Re: [PATCH net-next-2.6] net: speedup udp receive path

Le jeudi 29 avril 2010 à 09:17 -0400, jamal a écrit :

> Could we have some stat in there that shows IPIs being produced? I think
> it would help to at least observe any changes over variety of tests.
> I did try to patch my system during the first few tests to record IPIs
> but it seems to make more sense to have it as a perf stat.
> 
> > Even with 200.000 IPI per second, 'perf top -C CPU_IPI_sender' shows
> > that sending IPI is very cheap (maybe ~1% of cpu cycles)
> > 
> > # Samples: 32033467127
> > #
> 
> One thing i observed is our profiles seem different. Could you send me
> your .config for a single nehalem and i will try to go as close as
> possible to it? I have a sky2 instead of bnx - but i suspect everything
> else will be very similar...
> I apologize i dont have much time to look into details - but what i can
> do is test at least.

I'am going to redo some test on my 'old machine', with tg3 driver.

You could try following program :


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

struct softnet_stat_vals {
	int flip;
	unsigned int tab[2][10];
};

int read_file(struct softnet_stat_vals *v)
{
	char buffer[1024];
	FILE *F = fopen("/proc/net/softnet_stat", "r");

	v->flip ^= 1;
	if (!F)
		return -1;

	memset(v->tab[v->flip], 0, 10 * sizeof(unsigned int));
	while (fgets(buffer, sizeof(buffer), F)) {
		int i, pos = 0;
		unsigned int val;
	
		for (i = 0; ;) {
			if (sscanf(buffer + pos, "%08x", &val) != 1) break;
			v->tab[v->flip][i] += val;
			pos += 9;
			if (++i == 10)
				break;
			}
		}
	fclose(F);

}


int main(int argc, char *argv[])
{
	struct softnet_stat_vals *v = calloc(sizeof(struct softnet_stat_vals), 1);
	
	read_file(v);
	for (;;) {
		sleep(1);
		read_file(v);
		printf("%u rps\n", v->tab[v->flip][9] - v->tab[v->flip^1][9]);
	}
}


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