Re: [PATCH 00/13] Re: Scalability requirements for sysv ipc

[Nadia Derbey]

Peter Zijlstra wrote:
> On Mon, 2008-04-14 at 07:18 +0200, Nadia Derbey wrote:
>
> > Peter Zijlstra wrote:
> >
> > > On Fri, 2008-04-11 at 18:17 +0200, Nadia.Derbey@xxxxxxxx wrote:
> > >
> > >
> > > > Here is finally the ipc ridr-based implementation I was talking about last
> > > > week (see http://lkml.org/lkml/2008/4/4/208).
> > > > I couldn't avoid much of the code duplication, but at least made things
> > > > incremental.
> > > >
> > > > Does somebody now a test suite that exists for the idr API, that I could
> > > > run on this new api?
> > > >
> > > > Mike, can you try to run it on your victim: I had such a hard time building
> > > > this patch, that I couldn't re-run the test on my 8-core with this new
> > > > version. So the last results I have are for 2.6.25-rc3-mm1.
> > > >
> > > > Also, I think a careful review should be done to avoid introducing yet other
> > > > problems :-(
> > >
> > >
> > > Why duplicate the whole thing, when we converted the Radix tree to be
> > > RCU safe we did it in-place. Is there a reason this is not done for idr?
> >
> > I did that because I wanted to go fast and try to fix the performance 
> > problem we have with sysV ipc's. I didn't want to introduce (yet other) 
> > regressions in the code that uses idr's today and that works well ;-)
> > May be in the future if this rcu based api appears to be ok, we can 
> > replace one with the other?
>
>
> > From what I can see the API doesn't change at all,

Well, 1 interface changes, 1 is added and another one went away:

1) for the preload part (it becomes like the radix-tree preload part):

int idr_pre_get(struct idr *, gfp_t);
would become
int idr_pre_get(gfp_t);

2) idr_pre_get_end() is added (same as radix_tree_preload_end()).

3) The idr_init() disappears.

You might see that other interfaces are not provided by ridr, but this 
is only because I've taken those that are useful for the ipc part (so 
should not be a problem to make the whole thing rcu safe).

> so I don't see why
> you need to duplicate - either the new code works as expected or its
> broken.

That's why I asked for an "IDR test suite": I wanted to test potential 
regressions.

> If it works its good enough for all IDR users, if its broken we
> should fix it. Seems simple enough.. am I missing something obvious?

Regards,
Nadia




--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/