Re: [dpdk-dev] [PATCH v2] app/testpmd: fix testpmd packets dump overlapping

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 11/18/2020 6:09 PM, Jiawei(Jonny) Wang wrote:
> Hi Ferruh,
> 
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit@intel.com>
>> Sent: Tuesday, November 17, 2020 8:07 PM
>> To: Jiawei(Jonny) Wang <jiaweiw@nvidia.com>; wenzhuo.lu@intel.com;
>> beilei.xing@intel.com; bernard.iremonger@intel.com; Ori Kam
>> <orika@nvidia.com>; NBU-Contact-Thomas Monjalon
>> <thomas@monjalon.net>; Raslan Darawsheh <rasland@nvidia.com>
>> Cc: dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH v2] app/testpmd: fix testpmd packets dump
>> overlapping
>>
>> On 11/14/2020 12:01 PM, Jiawei Wang wrote:
>>> When testpmd enabled the verbosity for the received packets, if two
>>> packets was received at the same time, for example, sampling packet
>>> and normal packet, the dump output of these packets may be overlapping
>>> due to multiple core handled the multiple queues simultaneously.
>>>
>>> The patch uses one string buffer that collects all the packet dump
>>> output into this buffer and then printout it at last, that guarantee
>>> to printout separately the dump output per packet.
>>>
>>> Fixes: d862c45 ("app/testpmd: move dumping packets to a separate
>>> function")
>>>
>>> Signed-off-by: Jiawei Wang <jiaweiw@nvidia.com>
>>> ---
>>> v2:
>>> * Print dump output of per packet instead of per burst.
>>> * Add the checking for return value of 'snprintf' and exit if required size
>> exceed the print buffer size.
>>> * Update the log messages.
>>> ---
>>>    app/test-pmd/util.c | 378
>> ++++++++++++++++++++++++++++++++++++++++------------
>>>    1 file changed, 295 insertions(+), 83 deletions(-)
>>>
>>> diff --git a/app/test-pmd/util.c b/app/test-pmd/util.c index
>>> 649bf8f..ffae590 100644
>>> --- a/app/test-pmd/util.c
>>> +++ b/app/test-pmd/util.c
>>> @@ -12,15 +12,20 @@
>>>    #include <rte_vxlan.h>
>>>    #include <rte_ethdev.h>
>>>    #include <rte_flow.h>
>>> +#include <rte_log.h>
>>>
>>>    #include "testpmd.h"
>>>
>>> -static inline void
>>> -print_ether_addr(const char *what, const struct rte_ether_addr
>>> *eth_addr)
>>> +#define MAX_STRING_LEN 8192
>>
>> Isn't '8192' too large for a single packet, what do you think for '2048'?
>>
> 2K is ok for the normal case, here consider the case that registered mbuf dynamic flags names,
> Then total maximum length can reach to   64* RTE_MBUF_DYN_NAMESIZE = 4096
>   // char dynf_names[64][RTE_MBUF_DYN_NAMESIZE];
> So 2048 is not enough if all dynf_names be configured as maximum length of dyn_names.
> 
> How about the 5K? I think should be enough for now.

OK, and no need to be tight, if there are cases requesting longer string perhaps 
can keep the size as it is.

>> <...>
>>
>>> @@ -93,95 +103,269 @@
>>>    		is_encapsulation = RTE_ETH_IS_TUNNEL_PKT(packet_type);
>>>    		ret = rte_flow_get_restore_info(port_id, mb, &info, &error);
>>>    		if (!ret) {
>>> -			printf("restore info:");
>>> +			cur_len += snprintf(print_buf + cur_len,
>>> +					    buf_size - cur_len,
>>> +					    "restore info:");
>>
>> What do you think having a macro like below to simplfy the code:
>>
>>    #define FOO(buf, buf_size, cur_len, ...) \
>>    do { \
>>           if (cur_len >= buf_size) break; \
>>           cur_len += snprintf(buf + cur_len, buf_size - cur_len, __VA_ARGS__); \
>>    } while (0)
>>
>> It can be used as:
>>    FOO(print_buf, buf_size, cur_len, "restore info:");
>>
> Agree, will move these common code into a MARCO,
> I will use the  "MKDUMPSTR" as MARCO name,  means that  making a dump string buffer.
> 

Ack

>>> +			if (cur_len >= buf_size)
>>> +				goto error;
>>
>> This 'goto' goes out of the loop, not sure about breking the loop and not
>> processing all packets if buffer is out of space for one of the packets.
>> Anyway if you switch to macro above, the 'goto' is removed completely.
>>
> Use 'break' only break the do{} while and continue to following processing, but won't filled anymore into printbuf since it will break firstly in the MARCO checking.
> Or could use 'goto lable' instead 'break' in the marco?

I think cleaner to not have the 'goto', yes processing will continue but no 
space left case expected to happen very rare.