linux-kernel - Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

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Date:	Sun, 20 Oct 2013 17:29:10 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	sebastien.dugue@...l.net, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

On Fri, Oct 18, 2013 at 02:15:52PM -0700, Eric Dumazet wrote:
> On Fri, 2013-10-18 at 16:11 -0400, Neil Horman wrote:
> 
> > #define BUFSIZ_ORDER 4
> > #define BUFSIZ ((2 << BUFSIZ_ORDER) * (1024*1024*2))
> > static int __init csum_init_module(void)
> > {
> > 	int i;
> > 	__wsum sum = 0;
> > 	struct timespec start, end;
> > 	u64 time;
> > 	struct page *page;
> > 	u32 offset = 0;
> > 
> > 	page = alloc_pages((GFP_TRANSHUGE & ~__GFP_MOVABLE), BUFSIZ_ORDER);
> 
> Not sure what you are doing here, but its not correct.
> 
Why not?  You asked for a test with 32 hugepages, so I allocated 32 hugepages.

> You have a lot of variations in your results, I suspect a NUMA affinity
> problem.
> 
I do have some variation, you're correct, but I don't think its a numa issue

> You can try the following code, and use taskset to make sure you run
> this on a cpu on node 0
> 
I did run this with taskset to do exactly that (hence my comment above).  I'll
be glad to run your variant on monday morning though and provide results.


Best
Neil


> #define BUFSIZ 2*1024*1024
> #define NBPAGES 16
> 
> static int __init csum_init_module(void)
> {
>         int i;
>         __wsum sum = 0;
>         u64 start, end;
> 	void *base, *addrs[NBPAGES];
>         u32 rnd, offset;
> 
> 	memset(addrs, 0, sizeof(addrs));
> 	for (i = 0; i < NBPAGES; i++) {
> 		addrs[i] = kmalloc_node(BUFSIZ, GFP_KERNEL, 0);
> 		if (!addrs[i])
> 			goto out;
> 	}
> 
>         local_bh_disable();
>         pr_err("STARTING ITERATIONS on cpu %d\n", smp_processor_id());
>         start = ktime_to_ns(ktime_get());
>         
>         for (i = 0; i < 100000; i++) {
> 		rnd = prandom_u32();
> 		base = addrs[rnd % NBPAGES];
> 		rnd /= NBPAGES;
> 		offset = rnd % (BUFSIZ - 1500);
>                 offset &= ~1U;
>                 sum = csum_partial_opt(base + offset, 1500, sum);
>         }
>         end = ktime_to_ns(ktime_get());
>         local_bh_enable();
> 
>         pr_err("COMPLETED 100000 iterations of csum %x in %llu nanosec\n", sum, end - start);
> 
> out:
> 	for (i = 0; i < NBPAGES; i++)
> 		kfree(addrs[i]);
> 
>         return 0;
> }
> 
> static void __exit csum_cleanup_module(void)
> {
>         return;
> }
> 
> 
> 
> 
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