* Waiman Long <waiman.l...@hp.com> wrote:
> On a large system with many cores, massive creation or destruction
> of processes/threads can sometime cause a fair amount of spinlock
> contention in the pgd_lock used by the pgd_alloc() and pgd_free()
> functions. This patch tries to reduce false cacheline sharing by
> putting the pgd_lock in its own cacheline which help to reduce
> contention on the lock.
>
> Signed-off-by: Waiman Long <waiman.l...@hp.com>
> ---
> arch/x86/mm/fault.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 181c53b..fae48df 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -185,7 +185,7 @@ force_sig_info_fault(int si_signo, int si_code, unsigned
> long address,
> force_sig_info(si_signo, &info, tsk);
> }
>
> -DEFINE_SPINLOCK(pgd_lock);
> +__cacheline_aligned_in_smp DEFINE_SPINLOCK(pgd_lock);
> LIST_HEAD(pgd_list);
Yeah, so if you are seeing pgd_lock contention we could do a lot more to
improve
the performance of pgd allocation than just putting it on a separate cacheline:
we
can actually eliminate pgd_list and turn all pgd_list users into RCU walkers of
the tasklist lock, and make pgd_alloc()/pgd_free() lockless on x86.
I've done a series that implements this, I'll post it soon, please stay tuned!
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
