Re: [PATCH] net/pcap: reduce time for stopping device

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

On 8/25/2022 8:20 AM, Yiding Zhou wrote:
> The pcap file will be synchronized to the disk when stopping the device.
> It takes a long time if the file is large that would cause the
> 'detach sync request' timeout when the device is closed under multi-process
> scenario.
> 
> This commit fixes the issue by performing synchronization in Tx path
> 
> Fixes: 4c173302c307 ("pcap: add new driver")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Yiding Zhou <yidingx.zhou@intel.com>
> ---
>   drivers/net/pcap/pcap_ethdev.c | 18 ++++++++++++++++--
>   1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c
> index ec29fd6bc5..52eafa5674 100644
> --- a/drivers/net/pcap/pcap_ethdev.c
> +++ b/drivers/net/pcap/pcap_ethdev.c
> @@ -3,7 +3,7 @@
>    * Copyright(c) 2014 6WIND S.A.
>    * All rights reserved.
>    */
> -
> +#include <unistd.h>
>   #include <time.h>
>   
>   #include <pcap.h>
> @@ -38,6 +38,8 @@
>   
>   #define RTE_PMD_PCAP_MAX_QUEUES 16
>   
> +#define ETH_PCAP_SYNC_THRESHOLD 0x20000000
> +
>   static char errbuf[PCAP_ERRBUF_SIZE];
>   static struct timespec start_time;
>   static uint64_t start_cycles;
> @@ -47,6 +49,8 @@ static uint8_t iface_idx;
>   static uint64_t timestamp_rx_dynflag;
>   static int timestamp_dynfield_offset = -1;
>   
> +RTE_DEFINE_PER_LCORE(uint64_t, _pcap_cached_bytes);
> +
>   struct queue_stat {
>   	volatile unsigned long pkts;
>   	volatile unsigned long bytes;
> @@ -144,6 +148,16 @@ static struct rte_eth_link pmd_link = {
>   
>   RTE_LOG_REGISTER_DEFAULT(eth_pcap_logtype, NOTICE);
>   
> +static inline void
> +pcap_dumper_data_sync(pcap_dumper_t *dumper, uint32_t bytes)
> +{
> +	RTE_PER_LCORE(_pcap_cached_bytes) += bytes;
> +	if (unlikely(RTE_PER_LCORE(_pcap_cached_bytes) > ETH_PCAP_SYNC_THRESHOLD)) {
> +		if (!fdatasync(fileno(pcap_dump_file(dumper))))
> +			RTE_PER_LCORE(_pcap_cached_bytes) = 0;
> +	}
> +}
> +
>   static struct queue_missed_stat*
>   queue_missed_stat_update(struct rte_eth_dev *dev, unsigned int qid)
>   {
> @@ -421,7 +435,7 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>   	 * process stops and to make sure the pcap file is actually written,
>   	 * we flush the pcap dumper within each burst.
>   	 */
> -	pcap_dump_flush(dumper);
> +	pcap_dumper_data_sync(dumper, tx_bytes);

'pcap_dump_flush()' should be doing the same thing, to write buffer to 
file, isn't it working?

Can you check the return value of the 'pcap_dump_flush()' API, I wonder 
if it keeps failing, for some reason?

>   	dumper_q->tx_stat.pkts += num_tx;
>   	dumper_q->tx_stat.bytes += tx_bytes;
>   	dumper_q->tx_stat.err_pkts += nb_pkts - num_tx;