lkml.org 
[lkml]   [2009]   [Oct]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Commit 34d76c41 causes linker errors on ia64 with NR_CPUS=4096

* Jiri Kosina <jkosina@suse.cz> wrote:

> On Tue, 20 Oct 2009, Jiri Kosina wrote:
>
> > > Commit 34d76c41 introduced the update_shares_data percpu, but it ends up
> > > causing problems on large ia64 machines. Specifically, ia64 is limited
> > > to 64k in percpu vars and with NR_CPUS=4096, that ends up being 32k by
> > > itself. It ends up causing link errors since that is how ia64 enforces
> > > the 64k limit.
> > >
> > > I can take a deeper look at finding a workable solution but thought I'd
> > > mention it in case you had ideas already.
> >
> > I am adding some IA64 CCs, as the failure is solely caused by the ia64
> > percpu implementation/pagefault handler optimization which requires the
> > .percpu section area not be larger than 64k, which blows up with 34d76c41
> > and NR_CPUS high enoufh (due to introduction of percpu array being
> > size-dependent on NR_CPUS).
>
> How about this one? (untested)
>
>
>
> From: Jiri Kosina <jkosina@suse.cz>
> Subject: sched: move rq_weight data array out of .percpu
>
> Commit 34d76c41 introduced percpu array update_shares_data, size of which
> being proportional to NR_CPUS. Unfortunately this blows up ia64 for large
> NR_CPUS configuration, as ia64 allows only 64k for .percpu section.
>
> Fix this by allocating this array dynamically and keep only pointer to it
> percpu.
>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> ---
> kernel/sched.c | 15 +++++++--------
> 1 files changed, 7 insertions(+), 8 deletions(-)

Seems like an IA64 bug to me. It's _very_ easy to get more than 64K of
percpu data - i'm wondering why IA64 only triggered it now? Sure
lockdep/lockstat must have triggered it before.

Ingo


\
 
 \ /
  Last update: 2009-10-20 08:19    [W:0.098 / U:0.592 seconds]
©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site