On Wed, 1 Jul 2026 08:23:40 -0400 Steven Rostedt <[email protected]> wrote:
> On Wed, 1 Jul 2026 13:04:04 +0100 > David Laight <[email protected]> wrote: > > > > > Well, that would break trace-cmd. As reading the raw buffers clears the > > > trace, and trace-cmd reads the saved_cmdlines file *after* it reads the > > > trace, as during the trace it gets populated. > > > > So you'd need to clear it when tracing is enabled after the buffer is > > cleared. > > Just a matter of getting the timing right. > > Why? Note, saved_cmdlines is for *all* instances. You can have multiple > instances tracing different things and they still all use the one > saved_cmdlines file. It's not tied to any specific buffer. It's a cache. It > gets populated at the next schedule switch after an event occurs. > Mostly thoughts about the size of the cache and the difference between the apparent default size of 128 and the actual size of 6300. I had said that I'd not really looked at when it was used, just what it contained. None of that is relevant to this patch which just changes the data structures a bit. It also means that most updates will only dirty a single cache line. Indeed it is probably worth comparing the comm[] strings and only doing the write it they differ to avoid dirtying the cache line(s). David
