On Sat, Dec 18, 2010 at 10:23 AM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > You want to have a ring of events, and into that ring you also have a > "this event has been read" pointer. And you _never_ overwrite entries > that haven't been read yet, because quite frankly, if you get some > nasty memory corruption, you may end up with a thousand oopses in > rapid succession, and the latter ones are likely to be just fallout > from the earlier ones. So you definitely don't want to overwrite the > earlier ones, because they are more likely to contain the clues about > the actual original cause. > > At the same time, you do want to have the capability of saying "I've > seen this", and let it be overwritten. For example, if we end up > teaching syslogd or something like that to use this, syslogd would > write the oops to disk, do a fdatasync() on the oops file, and after > it's stable on disk it can mark it "read". > > Also, since this is very much about persistent storage, I think any > events from a previous boot that still exists should be marked "read". > You still want to be able to read them (so marking something "read" > does not mean that it goes away), but if a new oops happens, you don't > want some old entries from long ago to stop it from being written to > persistent storage. So if you don't have any syslogd or any other tool > that saves things to disk, you'd still get the new oopses into > persistent storage. > > Doesn't that sound like the best of both worlds? It sounds like an excellent heuristic for how the platform layer should manage the persistent store when space is tight. But I think that I can still keep my /dev/pstore filesystem as a presentation layer to make the bits available to the user in a device independent way. Or perhaps the pstore layer can help with the implementation of the heuristic. It knows what items are in the pstore, so it could build & maintain the "ring" and pass the id of the least wanted item down to the platform layer whenever it wants to write a record ... with the platform layer giving a status to say whether it had to delete that item to make space for the new one? -Tony -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
