Re: trace_printk issue. Was: [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF

2019-10-04 Thread Alexei Starovoitov
On 10/3/19 9:41 AM, Steven Rostedt wrote: > On Thu, 3 Oct 2019 09:18:40 -0700 > Alexei Starovoitov wrote: > >> I think dropping last events is just as bad. Is there a mode to overwrite old >> and keep the last N (like perf does) ? > > Well, it drops it by pages. Thus you should always have the l

Re: trace_printk issue. Was: [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF

2019-10-03 Thread Steven Rostedt
On Thu, 3 Oct 2019 09:18:40 -0700 Alexei Starovoitov wrote: > I think dropping last events is just as bad. Is there a mode to overwrite old > and keep the last N (like perf does) ? Well, it drops it by pages. Thus you should always have the last page of events. > Peter Wu brought this issue to

trace_printk issue. Was: [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF

2019-10-03 Thread Alexei Starovoitov
On Wed, Oct 02, 2019 at 07:00:27PM -0400, Steven Rostedt wrote: > > > > Both 'trace' and 'trace_pipe' have quirky side effects. > > Like opening 'trace' file will make all parallel trace_printk() to be > > ignored. > > While reading 'trace_pipe' file will clear it. > > >>>