On Wed, 2005-11-23 at 11:01 -0500, Alan Stern wrote:
> On Tue, 22 Nov 2005, Chandra Seetharaman wrote:
>
> > Hello,
> >
> > While making the notifier chain safe, i found room for some optimization.
> > Please comment on if it is worth pursuing.
> >
> > notifier_call_chain() calls registered callouts for _all_ events. But, many
> > of the callouts handle only few events.
> >
> > If we change notifier_call_chain() to call the callout only on registered
> > events, we can avoid few function overhead.
> >
> > Currently, events is of free format, we have to make it bit per event.
> > Among the existing users, ia64die_chain uses the highest number(25) of
> > events. i think 64 bit event would suffice.
> >
> > simplified logic:
> > notifier_call_chain(event)
> > {
> > if ((head->event & event) != 0)
> > return;
> > for_each_callout {
> > if ((notifier_block->event & event) != 0)
> > notifier_block->call(event);
> > }
> > }
>
> You would need to mask against (1ull << event), not against event.
> tset_bit() might work better.
event will be a bit field, not a sequential number.
>
> Do you really want to do this? It will mean changing every single
> notifier_block definition in the kernel, in addition to all the the
> notifier_heads. That's an awful lot of work for a relatively small gain.
Valid question. That is one of the reason of my posting this question.
I was planning to make the interface change to handle bitwise events
with zero being "all events". Future users will use the bitwise events.
w.r.t existing users, i would change only the macros(that were listed)
and let the module owners do the change to the notifier blocks when they
want (or file a kernel janitor bug).
The object was to move towards optimization.
> I believe that notifier_call_chain does not run very often, but I don't
> have any actual figures.
>
> Alan Stern
>
>
--
----------------------------------------------------------------------
Chandra Seetharaman | Be careful what you choose....
- [email protected] | .......you may get it.
----------------------------------------------------------------------
-
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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
