Messages in this thread |  | | | Date | Thu, 29 Sep 2011 21:40:57 -0700 | | From | Jeremy Fitzhardinge <> | | Subject | Re: [PATCH RFC 0/8] jump-label: allow early jump_label_enable() |
| |
On 09/29/2011 05:52 PM, Steven Rostedt wrote: > On Thu, 2011-09-29 at 16:26 -0700, Jeremy Fitzhardinge wrote: >> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> >> >> One big question which arises is whether the _early() function is >> necessary at all. All the stop_machine/mutex/etc stuff that >> arch_jump_label_transform() ends up doing is redundant pre-SMP, but it >> shouldn't hurt. Maybe we can just drop the _early function? It works >> on x86, at least, because jump_label_enable() works, which uses the full >> form. And dropping it would reduce this to a very much smaller series. > It does slow down the boot process, which is not a good thing when > everyone is pushing for the fastest restarts.
Would it really though? stop_machine() doesn't do very much when there are no other cpus.
Not that I measured or anything, but there was no obvious big lag at boot.
> What we should probably do is have a global read_mostly variable called, > smp_activated or something, then things that can be called before and > after can read this variable to determine if it can skip certain > protections.
Could do that if it turns out to be a problem.
> While we're at it, perhaps we could add a memory_initialized for things > like tracers that want to trace early but need to wait till it can > allocate buffers. If we had this flag, it could instead do an early > memory init to create the buffers.
That seems orthogonal to the jump_label changes.
J
|  |