hugepages on both sockets

hugepages on both sockets

[Lombardo, Ed]

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Hi,
I tried to pass into dpdk_eal_init() the argument --socket-mem=2048,2048" and I get segmentation error when strsplit() function is called
        arg_num = rte_strsplit(strval, len,
                        arg, RTE_MAX_NUMA_NODES, ',');


In eal_common_string_fns.c gdb failed at the line shown below.
rte_strsplit(char *string, int stringlen,
             char **tokens, int maxtokens, char delim)
{
        int i, tok = 0;
        int tokstart = 1; /* first token is right at start of string */

        if (string == NULL || tokens == NULL)
                goto einval_error;

        for (i = 0; i < stringlen; i++) {
                if (string[i] == '\0' || tok >= maxtokens)
                        break;
                if (tokstart) {
                        tokstart = 0;
                        tokens[tok++] = &string[i];
                }
                if (string[i] == delim) {
                        string[i] = '\0';    <<<< Fails here with segmentation fault.
                        tokstart = 1;
                }
        }
        return tok;

If I pass "--socket_mem=2048", --socket-mem=2048", rte_eal_init() does not complain.
Not sure if this would ensure both CPU sockets will host 2-1G hugepages?  I suspect it doesn't because I only see to rtemap_0 and rtemap_1 in /mnt/huge directory.  I think I should see four total.

# /opt/dpdk/dpdk-hugepages.py -s
Node Pages Size Total
0    2     1Gb    2Gb
1    2     1Gb    2Gb

I don't know if I should believe the above output showing 2Gb on Numa Nodes 0 and 1.

Any help is appreciated.

Thanks,
Ed

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Re: hugepages on both sockets

[Dmitry Kozlyuk]

Hi Ed,

On 05.04.2025 01:24, Lombardo, Ed wrote:
>
> Hi,
>
> I tried to pass into dpdk_eal_init() the argument 
> --socket-mem=2048,2048” and I get segmentation error when strsplit() 
> function is called
>
>         arg_num = rte_strsplit(strval, len,
>
>                         arg, RTE_MAX_NUMA_NODES, ',');
>
Please forgive me for the stupid question:
"strval" points to a mutable buffer, like "char strval[] = "2048,2048", 
not "char *strval = "2048,2048"?

> If I pass “--socket_mem=2048”, --socket-mem=2048”, rte_eal_init() does 
> not complain.
>
> Not sure if this would ensure both CPU sockets will host 2-1G 
> hugepages?  I suspect it doesn’t because I only see to rtemap_0 and 
> rtemap_1 in /mnt/huge directory.  I think I should see four total.
>
> # /opt/dpdk/dpdk-hugepages.py -s
>
> Node Pages Size Total
>
> 0    2     1Gb    2Gb
>
> 1    2     1Gb    2Gb
>
> I don’t know if I should believe the above output showing 2Gb on Numa 
> Nodes 0 and 1.
>
You are correct, --socket-mem=2048 allocates 2048 MB total, spreading 
between nodes.

RE: hugepages on both sockets

[Lombardo, Ed]

Hi Dmitry,
You pointed out a good point.  I passed the literal "--socket-mem=2048,2048" in the array provided to rte_eal_init() function, where DPDK EAL tries to tokenize in place the string and it crashes trying to modify a readonly memory.  I don't know why DPDK does this.  But now I know, and I now see four rtemap_x files created for two sockets.

Thank you,
Ed

-----Original Message-----
From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com> 
Sent: Friday, April 4, 2025 6:40 PM
To: Lombardo, Ed <Ed.Lombardo@netscout.com>; users@dpdk.org
Subject: Re: hugepages on both sockets

External Email: This message originated outside of NETSCOUT. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Hi Ed,

On 05.04.2025 01:24, Lombardo, Ed wrote:
>
> Hi,
>
> I tried to pass into dpdk_eal_init() the argument 
> --socket-mem=2048,2048” and I get segmentation error when strsplit() 
> function is called
>
>         arg_num = rte_strsplit(strval, len,
>
>                         arg, RTE_MAX_NUMA_NODES, ',');
>
Please forgive me for the stupid question:
"strval" points to a mutable buffer, like "char strval[] = "2048,2048", not "char *strval = "2048,2048"?

> If I pass “--socket_mem=2048”, --socket-mem=2048”, rte_eal_init() does 
> not complain.
>
> Not sure if this would ensure both CPU sockets will host 2-1G 
> hugepages?  I suspect it doesn’t because I only see to rtemap_0 and
> rtemap_1 in /mnt/huge directory.  I think I should see four total.
>
> # /opt/dpdk/dpdk-hugepages.py -s
>
> Node Pages Size Total
>
> 0    2     1Gb    2Gb
>
> 1    2     1Gb    2Gb
>
> I don’t know if I should believe the above output showing 2Gb on Numa 
> Nodes 0 and 1.
>
You are correct, --socket-mem=2048 allocates 2048 MB total, spreading between nodes.

Re: hugepages on both sockets

[Stephen Hemminger]

On Sun, 6 Apr 2025 00:56:45 +0000
"Lombardo, Ed" <Ed.Lombardo@netscout.com> wrote:

> Hi Dmitry,
> You pointed out a good point.  I passed the literal "--socket-mem=2048,2048" in the array provided to rte_eal_init() function, where DPDK EAL tries to tokenize in place the string and it crashes trying to modify a readonly memory.  I don't know why DPDK does this.  But now I know, and I now see four rtemap_x files created for two sockets.

The function rte_eal_init() expects arguments to be like the arguments passed to main().
Those arguments are not read-only. You need to use strdup (or strdupa) to make mutable versions.