On 8/20/24 15:55, Mike Pattrick wrote:
> Clang analyzer will complain about floating point operations conducted
> with integer types as rounding is undefined. In pmd_info_show_rxq() a
> percentage was calculated inside uint64 integers instead of a floating
> pointer variable for a user visible message. There isn't a good reason
> not to use floating point types here.
I don't see a good reason to use floating point arithmetic here. We're using
integer division here and we are not interested in fractional parts. So, I'm
a little confused on why this is a problem.
Is it because the '100' has an ambiguous type? Will it still complain if we
use '100ULL' or UINT64_C(100) ?
Best regards, Ilya Maximets.
>
> Signed-off-by: Mike Pattrick <m...@redhat.com>
> ---
> lib/dpif-netdev.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index f0594e5f5..69d5ddfa1 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -900,8 +900,8 @@ pmd_info_show_rxq(struct ds *reply, struct
> dp_netdev_pmd_thread *pmd,
> if (pmd->core_id != NON_PMD_CORE_ID) {
> struct rxq_poll *list;
> size_t n_rxq;
> - uint64_t total_pmd_cycles = 0;
> - uint64_t busy_pmd_cycles = 0;
> + double total_pmd_cycles = 0;
> + double busy_pmd_cycles = 0;
> uint64_t total_rxq_proc_cycles = 0;
> unsigned int intervals;
>
> @@ -930,7 +930,7 @@ pmd_info_show_rxq(struct ds *reply, struct
> dp_netdev_pmd_thread *pmd,
> for (int i = 0; i < n_rxq; i++) {
> struct dp_netdev_rxq *rxq = list[i].rxq;
> const char *name = netdev_rxq_get_name(rxq->rx);
> - uint64_t rxq_proc_cycles = 0;
> + double rxq_proc_cycles = 0;
>
> rxq_proc_cycles = get_interval_values(rxq->cycles_intrvl,
> &rxq->intrvl_idx,
> @@ -942,9 +942,8 @@ pmd_info_show_rxq(struct ds *reply, struct
> dp_netdev_pmd_thread *pmd,
> ? "(enabled) " : "(disabled)");
> ds_put_format(reply, " pmd usage: ");
> if (total_pmd_cycles) {
> - ds_put_format(reply, "%2"PRIu64"",
> - rxq_proc_cycles * 100 / total_pmd_cycles);
> - ds_put_cstr(reply, " %");
> + ds_put_format(reply, "%2.0f %%",
> + (rxq_proc_cycles * 100) / total_pmd_cycles);
> } else {
> ds_put_format(reply, "%s", "NOT AVAIL");
> }
> @@ -954,13 +953,14 @@ pmd_info_show_rxq(struct ds *reply, struct
> dp_netdev_pmd_thread *pmd,
> if (n_rxq > 0) {
> ds_put_cstr(reply, " overhead: ");
> if (total_pmd_cycles) {
> - uint64_t overhead_cycles = 0;
> + double overhead_cycles = 0;
>
> if (total_rxq_proc_cycles < busy_pmd_cycles) {
> overhead_cycles = busy_pmd_cycles -
> total_rxq_proc_cycles;
> }
> - ds_put_format(reply, "%2"PRIu64" %%",
> - overhead_cycles * 100 / total_pmd_cycles);
> +
> + ds_put_format(reply, "%2.0f %%",
> + (overhead_cycles * 100) / total_pmd_cycles);
> } else {
> ds_put_cstr(reply, "NOT AVAIL");
> }
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