Re: [dpdk-dev] [PATCH v2] eal: add additional info if lcore exceeds max cores

[David Hunt <david.hunt@intel.com>]

Hi David,

On 16/9/2021 1:34 PM, David Marchand wrote:
> On Wed, Sep 15, 2021 at 2:11 PM David Hunt <david.hunt@intel.com> wrote:
>> If the user requests to use an lcore above 128 using -l or -c,
>> the eal will exit with "EAL: invalid core list syntax" and
>> very little other useful information.
>>
>> This patch adds some extra information suggesting to use --lcores
>> so that physical cores above RTE_MAX_LCORE (default 128) can be
>> used. This is achieved by using the --lcores option by mapping
>> the logical cores in the application onto to physical cores.
>>
>> There is no change in functionalty, just additional messages
>> suggesting how the --lcores option might be used for the supplied
>> list of lcores. For example, if "-l 12-14,130,132" is used, we
>> see the following additional output on the command line:
>>
>> EAL: Error = One of the 5 cores provided exceeds RTE_MAX_LCORE (128)
>> EAL: Please use --lcores instead, e.g. --lcores 0@12,1@13,2@14,3@130,4@132
>>
>> Signed-off-by: David Hunt <david.hunt@intel.com>
>>
>> ---
>> changes in v2
>>     * Rather than increasing the default max lcores (as in v1),
>>       it was agreed to do this instead (switch to --lcores).
>>     * As the other patches in the v1 of the set are no longer related
>>       to this change, I'll submit as a separate patch set.
> The -c option can use the same kind of warning.


Agreed, I'll include in the next version.


>
>> ---
>>   lib/eal/common/eal_common_options.c | 31 +++++++++++++++++++++++++----
>>   1 file changed, 27 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/eal/common/eal_common_options.c b/lib/eal/common/eal_common_options.c
>> index ff5861b5f3..5c7a5a45a5 100644
>> --- a/lib/eal/common/eal_common_options.c
>> +++ b/lib/eal/common/eal_common_options.c
>> @@ -836,6 +836,8 @@ eal_parse_service_corelist(const char *corelist)
>>          return 0;
>>   }
>>
>> +#define MAX_LCORES_STRING 512
>> +
>>   static int
>>   eal_parse_corelist(const char *corelist, int *cores)
>>   {
>> @@ -843,6 +845,9 @@ eal_parse_corelist(const char *corelist, int *cores)
>>          char *end = NULL;
>>          int min, max;
>>          int idx;
>> +       bool overflow = false;
>> +       char lcores[MAX_LCORES_STRING] = "";
> This code is not performance sensitive.
> In the worst case, like for RTE_MAX_LCORES lcores, it gives this:
> 0@0,1@1,2@2,3@3,4@4,5@5,6@6,7@7,8@8,9@9,10@10,11@11,12@12,13@13,14@14,15@15,16@16,17@17,18@18,19@19,20@20,21@21,22@22,23@23,24@24,25@25,26@26,27@27,28@28,29@29,30@30,31@31,32@32,33@33,34@34,35@35,36@36,37@37,38@38,39@39,40@40,41@41,42@42,43@43,44@44,45@45,46@46,47@47,48@48,49@49,50@50,51@51,52@52,53@53,54@54,55@55,56@56,57@57,58@58,59@59,60@60,61@61,62@62,63@63,64@64,65@65,66@66,67@67,68@68,69@69,70@70,71@71,72@72,73@73,74@74,75@75,76@76,77@77,78@78,79@79,80@80,81@81,82@82,83@83,84@84,85@85,86@86,87@87,88@88,89@89,90@90,91@91,92@92,93@93,94@94,95@95,96@96,97@97,98@98,99@99,100@100,101@101,102@102,103@103,104@104,105@105,106@106,107@107,108@108,109@109,110@110,111@111,112@112,113@113,114@114,115@115,116@116,117@117,118@118,119@119,120@120,121@121,122@122,123@123,124@124,125@125,126@126,127@127,
>
> Which is 800+ bytes long, let's switch do dynamic allocations.
>

Good point. I'll allocate a dozen bytes or so for each physical core 
detected, that should be enough.


>
>> +       int len = 0;
>>
>>          for (idx = 0; idx < RTE_MAX_LCORE; idx++)
>>                  cores[idx] = -1;
>> @@ -862,8 +867,10 @@ eal_parse_corelist(const char *corelist, int *cores)
>>                  idx = strtol(corelist, &end, 10);
>>                  if (errno || end == NULL)
>>                          return -1;
>> -               if (idx < 0 || idx >= RTE_MAX_LCORE)
>> +               if (idx < 0)
>>                          return -1;
>> +               if (idx >= RTE_MAX_LCORE)
>> +                       overflow = true;
> The code before was intermixing parsing and validation of values.
> This intermix was not that great.
> Let's separate those concerns.

I see what you mean (in your comments below). Agreed this would be a 
good idea.


>
>>                  while (isblank(*end))
>>                          end++;
>>                  if (*end == '-') {
>> @@ -873,10 +880,19 @@ eal_parse_corelist(const char *corelist, int *cores)
>>                          if (min == RTE_MAX_LCORE)
>>                                  min = idx;
>>                          for (idx = min; idx <= max; idx++) {
>> -                               if (cores[idx] == -1) {
>> -                                       cores[idx] = count;
>> -                                       count++;
>> +                               if (idx < RTE_MAX_LCORE) {
>> +                                       if (cores[idx] == -1)
>> +                                               cores[idx] = count;
>>                                  }
>> +                               count++;
>> +                               if (count == 1)
>> +                                       len = len + snprintf(&lcores[len],
>> +                                                       MAX_LCORES_STRING - len,
>> +                                                       "%d@%d", count-1, idx);
>> +                               else
>> +                                       len = len + snprintf(&lcores[len],
>> +                                                       MAX_LCORES_STRING - len,
>> +                                                       ",%d@%d", count-1, idx);
> Always appending a , is easier to read, then after the loop, you just
> need to trim the last ,.

Sure.


>
>>                          }
>>                          min = RTE_MAX_LCORE;
>>                  } else
>> @@ -886,6 +902,13 @@ eal_parse_corelist(const char *corelist, int *cores)
>>
>>          if (count == 0)
>>                  return -1;
>> +       if (overflow) {
>> +               RTE_LOG(ERR, EAL, "Error = One of the %d cores provided exceeds RTE_MAX_LCORE (%d)\n",
>> +                               count, RTE_MAX_LCORE);
>> +               RTE_LOG(ERR, EAL, "Please use --lcores instead, e.g. --lcores %s\n",
>> +                               lcores);
>> +               return -1;
>> +       }
>>          return 0;
>
> I'd rework both -c and -l parsing to fill a common data structure,
> then validate and generate the suggestion in common helpers.


OK, I'll take a look.



> Something like: https://github.com/david-marchand/dpdk/commit/lcores
> This probably needs some time to look at to enhance style and
> carefully check for mem leaks.
> Tested with max_lcores = 4 (for my 8 cores laptop):
>
> $ for opt in "-c 0x" "-c 0x0" "-c 0x1" "-c 0xf" "-c 0x10" "-c 0x1f"
> "-c 0x11" "-c 0x30" "-l 0" "-l 0-3" "-l 0-3,2" "-l 4" "-l 0-4" "-l
> 0,4" "-l 4,5"
> do
>    echo $opt
>    echo quit | build/app/dpdk-testpmd $opt --log-level=lib.eal:debug
> --no-huge -m 20 -a 0:0.0 -- --total-num-mbufs=2048 -ia |&
>      grep -E '(ready|RTE_MAX_LCORE|Please use|No lcore|Too many)'
>    echo
> done
>
> -c 0x
> EAL: No lcore in coremask: 0x
>
> -c 0x0
> EAL: No lcore in coremask: 0x0
>
> -c 0x1
> EAL: Main lcore 0 is ready (tid=7f03956d1c00;cpuset=[0])
>
> -c 0xf
> EAL: Main lcore 0 is ready (tid=7fe464461c00;cpuset=[0])
> EAL: lcore 1 is ready (tid=7fe45f924700;cpuset=[1])
> EAL: lcore 2 is ready (tid=7fe45f123700;cpuset=[2])
> EAL: lcore 3 is ready (tid=7fe45e922700;cpuset=[3])
>
> -c 0x10
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@4
>
> -c 0x1f
> EAL: Too many lcores in coremask: 0x1f
>
> -c 0x11
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@0,1@4
>
> -c 0x30
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: lcore 5 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@4,1@5
>
> -l 0
> EAL: Main lcore 0 is ready (tid=7f833b17ac00;cpuset=[0])
>
> -l 0-3
> EAL: Main lcore 0 is ready (tid=7f9ff5216c00;cpuset=[0])
> EAL: lcore 2 is ready (tid=7f9fefed8700;cpuset=[2])
> EAL: lcore 3 is ready (tid=7f9fef6d7700;cpuset=[3])
> EAL: lcore 1 is ready (tid=7f9ff06d9700;cpuset=[1])
>
> -l 0-3,2
> EAL: Main lcore 0 is ready (tid=7f106b937c00;cpuset=[0])
> EAL: lcore 1 is ready (tid=7f1066dfa700;cpuset=[1])
> EAL: lcore 2 is ready (tid=7f10665f9700;cpuset=[2])
> EAL: lcore 3 is ready (tid=7f1065df8700;cpuset=[3])
>
> -l 4
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@4
>
> -l 0-4
> EAL: Too many lcores in core list: 0-4
>
> -l 0,4
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@0,1@4
>
> -l 4,5
> EAL: lcore 4 >= RTE_MAX_LCORE (4)
> EAL: lcore 5 >= RTE_MAX_LCORE (4)
> EAL: Please use --lcores 0@4,1@5
>
>