Hi Mathieu, On Tue, Apr 16, 2024 at 10:49 AM Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > > On 2024-04-16 10:41, Alexander Aring wrote: > > Hi all, > > > > I have an idea about using the DMA rings of a networking card as a > > tracing buffer. > > The first thing I'd be worried about is overhead caused by > false-sharing if you trace a large SMP/many-core system all > into the same global NIC buffer. The cache lines will bounce > left and right which is bad performance-wise. > modern NICs have several tx and rx dma rings. There is an ethtool command to query the number: sudo ethtool -g $IFACE so it depends on the hardware if you can pin one or more rings on a per-cpu buffer basis. I hope that somehow helps to make this idea less worrisome. Thanks. - Alex
|