On Thu 2019-03-28 16:12:28, Steven Rostedt wrote: > On Thu, 28 Mar 2019 12:45:18 -0700 > Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > > > > I see solution is simple, but now we have a loop with GFP_ATOMIC > > > allocations inside. How many "tracing spus" is this expected to loop > > > over? Will not it exhaust atomically available pages and reliably fail > > > in common configurations? > > > Pavel > > > > Each one of these allocations is ~32 bytes and you do one per CPU. > > Even with systems with a lot of CPUs that's not going to be tons. > > ...and you only do it with GFP_ATOMIC when you're actively dropped > > into kdb and debugging. It seems like going for simplicity is the > > right call here, but of course if Steven or Daniel say that it has to > > be done a different way then they're the true authorities. > > I really don't care. The code in question is only affected when we have > CONFIG_KGDB_KDB enabled. But as it gets called from an atomic context, > is it any different than what it was doing before? Except now with > GFP_ATOMIC it is actually safer. > > Now, we could add some helper functions in the ring-buffer code to > allow us to pre-allocate the ring_buffer_iter at boot up. Then we could > pass in the per-allocated iters and use them here. Ok, I guess 32 bytes is small enough, I somehow imagined it would be bigger... -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
