Messages in this thread | | | Date | Mon, 8 Jun 2009 22:52:37 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] latencytop: note task_struct bloat |
| |
* Hugh Dickins <hugh.dickins@tiscali.co.uk> wrote:
> Add belated comment to LATENCYTOP help text, making clear that this is a > much more expensive option than you might think: along with the options > it selects, it may add more than 4000 bytes to each struct task_struct > (on 64-bit; more than 2000 on 32-bit), effectively quadrupling the size > of an otherwise lean task_struct (in fact, slab on x86_64 fits only 1 > in two pages, whereas it fits 5 in two pages without LATENCYTOP=y). > > Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> > --- > > lib/Kconfig.debug | 4 ++++ > 1 file changed, 4 insertions(+) > > --- 2.6.30-rc8/lib/Kconfig.debug 2009-05-16 10:26:16.000000000 +0100 > +++ linux/lib/Kconfig.debug 2009-06-08 18:30:50.000000000 +0100 > @@ -826,6 +826,10 @@ config LATENCYTOP > Enable this option if you want to use the LatencyTOP tool > to find out which userspace is blocking on what kernel operations. > > + Note: enabling this option may add more than 4000 bytes to each > + task_struct on a 64-bit kernel (more than 2000 bytes to task_struct > + on a 32-bit kernel), multiplying its memory usage by 4 or even 5. > +
Ah, nasty - quadratics in action.
This should be improved really. Arjan, what would it take to convert latencytop over to perfcounters? What would be ideal software counter for this?
Ingo
| |