Ingo Molnar <[EMAIL PROTECTED]> writes: > * Eric W. Biederman <[EMAIL PROTECTED]> wrote: > >> >> Well struct pid * works in that case if you grab the reference to >> >> it. >> > >> > but the display of the stats might happen much later. The point of >> > this API is to save pid+comm, which gives users a good idea about >> > what caused the events in the past - without having to pin any >> > resource of that task. >> >> Likewise struct pid is designed not to be a problem if pinned. It is a >> little heavier then it used to be with the addition of pid namespace >> support but not much. And if it is to heavy struct pid needs to be >> fixed. >> >> Holding the struct pid very much does not pin the task struct, and it >> shouldn't pin any other resources. I agree 64bytes or so is a bit >> more to pin then 4 bytes but it really isn't a lot. > > yeah, and i have no conceptual objections - i just wanted to outline the > thinking behind /proc/timer_stats.
Sure. Appreciated. Outlining the thinking in the other direction struct pid is supposed to be the pid representation in the kernel. All of the pid_t stuff really should be pushed as close to the kernel/user boundary as possible. The closer I get to that ideal the more cases I find that we need to handle like /proc/timer_stats and the closer we get to having a complete pid namespace. <pant pant pant> A struct pid is also now all you pin (besides the inevitable file, dentry, inode trio) when you open a directory in /proc. So the task can be freed. Which removed some low-mem exhaustion scenarios when we introduced it. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
