[dpdk-dev] remove dpdk-pdump pcap file, disk space is not freed

[Ferruh Yigit]

On 8/23/2021 5:14 AM, Yan, Xiaoping (NSB - CN/Hangzhou) wrote:
> Hi,
> 
> Before I run pdump, 21MB is used in /tmp
> tmpfs                        63G   21M   63G   1% /tmp
> Then I run pdump with such command:
> dpdk-pdump  -c 0x4001000400100 -a 0000:03:00.6 -a 0000:03:06.1 --legacy-mem --base-virtaddr 0x2aaa2aa000 --file-prefix l2rt --  --pdump port=1,queue=*,rx-dev=/tmp/l2biprt.pcap,tx-dev=/tmp/l2biprt.pcap,mbuf-size=10240,total-num-mbufs=10000
> After stop, it generates a 14MB file
>               -rw-rw-r--. 1 9999 9999  14M Aug 23 03:58 l2biprt.pcap
> And 35M is used in /tmp
>               tmpfs                        63G   35M   63G   1% /tmp
> And fuser show there are still several users of this file. (all these pids are of running dpdk primary and secondary processes )
>               # fuser /tmp/l2biprt.pcap
> /tmp/l2biprt.pcap:     139   342   347   434
> Then after I rm the file (l2biprt.pcap), disk space in tmp is not freed (still 35MB used)
>               rm l2biprt.pcap
>               df -h
>               tmpfs                        63G   35M   63G   1% /tmp
> 
> 
> It seems it goes like this:
>              pdump start->pdump send vdev hotplug add request->primary and secondary process calls pmd_pcap_probe() which opens the pcap file->
>               pdump stop-> pdump send vdev hotplug remove request-> primary and secondary process does not close the pcap file
> 
> To properly close the pcap file and release disk space, it seems we should:
> 
>   *   somehow close the pcap file in "vdev hotplug remove", or
>   *   don't open the pcap file in "vdev hotplug add"( pmd_pcap_probe()), it seems pcap eth_dev_start will open the pcap file in case it was not opened.
> 
> Any comment is appreciated, thank you.


Hi Yan,

I can't reproduce the behavior you mentioned, for my case the .pcap file is
closed when pdump is terminated and there is no active user of the file after
that point.

Removing the pcap device cause closing the .pcap files.

When you terminate pdump application it will remove the pcap devices, and since
it is a secondary process a message sent to primary to remove it too, making
both process closing the pcap files.

When I use testpmd as primary application, I am getting following log from
testpmd when pdump terminated:
"Port 2 is closed"
Can you please test with testpmd? You can use '--log-level=*:debug' eal
parameter to get more log for multi process communication.

Btw, what is your DPDK version? I tested with latest DPDK (21.11.0-rc0).