[dpdk-dev] xstats performance
Olivier MATZ
olivier.matz at 6wind.com
Wed Jun 29 17:38:33 CEST 2016
Hi Remy,
While adapting an application to the new xstats API, I discovered
that it may not be so efficient to display the statistics and their
names.
I think the test-pmd code illustrates the issue pretty well:
/* Display xstats */
for (idx_xstat = 0; idx_xstat < cnt_xstats; idx_xstat++)
for (idx_name = 0; idx_name < cnt_xstats; idx_name++)
if (xstats_names[idx_name].id == xstats[idx_xstat].id) {
printf("%s: %"PRIu64"\n",
xstats_names[idx_name].name,
xstats[idx_xstat].value);
break;
}
The displaying is in O(n^2).
It's possible to enhance the code to have it in O(n), but it
requires an intermediate table.
Why not changing this:
struct rte_eth_xstat {
uint64_t id;
uint64_t value;
};
struct rte_eth_xstat_name {
char name[RTE_ETH_XSTATS_NAME_SIZE];
uint64_t id;
};
Into this:
struct rte_eth_xstat {
uint64_t id;
uint64_t value;
};
struct rte_eth_xstat_name {
char name[RTE_ETH_XSTATS_NAME_SIZE];
/* No identifier */
};
And assume that the id field in rte_eth_xstat corresponds to
the index in the rte_eth_xstat_name table?
The test-pmd code would be something like this:
/* Display xstats */
for (idx_xstat = 0; idx_xstat < cnt_xstats; idx_xstat++) {
printf("%s: %"PRIu64"\n",
xstats_names[xstats[idx_xstats].id].name,
xstats[idx_xstat].value);
}
What do you think?
Regards
Olivier
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