From: Steven Rostedt > Sent: 27 March 2020 01:46 > On Sat, 21 Mar 2020 19:13:51 +0000 > David Laight <David.Laight@xxxxxxxxxx> wrote: > > > From: Steven Rostedt > > > Sent: 19 March 2020 23:22 > > ... > > > > > > This patch series attempts to satisfy that request, by creating a > > > temporary buffer in each of the per cpu iterators to place the > > > read event into, such that it can be passed to users without worrying > > > about a writer to corrupt the event while it was being written out. > > > It also uses the fact that the ring buffer is broken up into pages, > > > where each page has its own timestamp that gets updated when a > > > writer crosses over to it. By copying it to the temp buffer, and > > > doing a "before and after" test of the time stamp with memory barriers, > > > can allow the events to be saved. > > > > Does this mean the you will no longer be able to look at a snapshot > > of the trace by running 'less trace' (and typically going to the end > > to get info for all cpus). > > I changed patch 9 to be this: > > It adds an option "pause-on-trace" that when set, will bring back the > old behavior of pausing recording to the ring buffer when the trace > file is open. > > If needed, I can add a kernel command line option and a Kconfig that > makes this set to true by default. Maybe a different file 'trace_no_pause' ? Along with the one that lets you read the raw trace and get EOF. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
