> -----Original Message-----
> From: lng-odp [mailto:[email protected]] On Behalf Of
> EXT Ivan Khoronzhuk
> Sent: Friday, September 11, 2015 1:05 PM
> To: [email protected]
> Subject: [lng-odp] [PATCH v2 5/5] performance: odp_pktio_perf: fix
> potential overflow for burst_gap
>
> The direct comparing of "cur_cycles" and "next_tx_cycles" is not
> valid, as "next_tx_cycles" can be overflowed and comparison will
> give wrong result. So use odp_time_diff_cycles() for that, as it
> takes in account ticks overflow.
>
> Signed-off-by: Ivan Khoronzhuk <[email protected]>
> ---
> test/performance/odp_pktio_perf.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/test/performance/odp_pktio_perf.c
> b/test/performance/odp_pktio_perf.c
> index ac32b15..85ef2bc 100644
> --- a/test/performance/odp_pktio_perf.c
> +++ b/test/performance/odp_pktio_perf.c
> @@ -303,7 +303,7 @@ static void *run_thread_tx(void *arg)
> int thr_id;
> odp_queue_t outq;
> pkt_tx_stats_t *stats;
> - uint64_t next_tx_cycles, start_cycles, cur_cycles, send_duration;
> + uint64_t burst_start_cycles, start_cycles, cur_cycles,
> send_duration;
> uint64_t burst_gap_cycles;
> uint32_t batch_len;
> int unsent_pkts = 0;
> @@ -334,11 +334,12 @@ static void *run_thread_tx(void *arg)
>
> cur_cycles = odp_time_cycles();
> start_cycles = cur_cycles;
> - next_tx_cycles = cur_cycles;
> + burst_start_cycles = odp_time_diff_cycles(cur_cycles,
> burst_gap_cycles);
Shouldn't this be:
burst_start_cycles = cur_cycles + burst_gap_cycles;
,which works as long as cycle count wraps at UINT64_MAX. Maybe we need a cpu.h
API for summing two values with correct wrapping.
-Petri
> while (odp_time_diff_cycles(start_cycles, cur_cycles) <
> send_duration) {
> unsigned alloc_cnt = 0, tx_cnt;
>
> - if (cur_cycles < next_tx_cycles) {
> + if (odp_time_diff_cycles(burst_start_cycles, cur_cycles)
> + < burst_gap_cycles) {
> cur_cycles = odp_time_cycles();
> if (idle_start == 0)
> idle_start = cur_cycles;
> @@ -351,7 +352,7 @@ static void *run_thread_tx(void *arg)
> idle_start = 0;
> }
>
> - next_tx_cycles += burst_gap_cycles;
> + burst_start_cycles += burst_gap_cycles;
>
> alloc_cnt = alloc_packets(tx_event, batch_len -
> unsent_pkts);
> if (alloc_cnt != batch_len)
> --
> 1.9.1
>
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