Re: [PATCH net-next] net: dev: introduce netdev_drop_inc()

On Wed, 09 Feb 2022 07:27:44 +0000 yajun.deng@linux.dev wrote:

February 9, 2022 11:53 AM, "Jakub Kicinski" [off-list ref] wrote:

quoted

IIRC perf support filters, I think with -f? We can't add a tracepoint
for every combination of attributes.  

Yes, we can use a command like this: " sudo perf record -g -a -e skb:kfree_skb --filter 'protocol == 0x0800' ",
However, only the filter is defined in kfree_skb tracepoint are available.

The purpose of this patch is record {rx_dropped, tx_dropped, rx_nohandler} in struct net_device, to distinguish 
with struct net_device_stats. 

We don't have any tracepoint records {rx_dropped, tx_dropped, rx_nohandler} in struct net_device now. 
Can we add {rx_dropped, tx_dropped, rx_nohandler} in kfree_skb tracepoint?  like this:

        TP_STRUCT__entry(
                __field(void *,         skbaddr)
                __field(void *,         location)
                __field(unsigned short, protocol)
                __field(enum skb_drop_reason,   reason)
                __field(unsigned long,  rx_dropped)
                __field(unsigned long,  tx_dropped)
                __field(unsigned long,  rx_nohandler)

        ),

        TP_fast_assign(
                __entry->skbaddr = skb;
                __entry->location = location;
                __entry->protocol = ntohs(skb->protocol);
                __entry->reason = reason;
                __entry->rx_dropped   = (unsigned long)atomic_long_read(&skb->dev->rx_dropped);
                __entry->tx_dropped   = (unsigned long)atomic_long_read(&skb->dev->tx_dropped);
                __entry->rx_nohandler = (unsigned long)atomic_long_read(&skb->dev->rx_nohandler);
        ),

If so, we can record this but not add a tracepoint.

You can use bpftrace to dereference extra information.