Messages in this thread | | | From | "Shai Fultheim ()" <> | Date | Wed, 6 Jun 2012 18:18:12 -0400 | Subject | RE: [tip:x86/mm] x86/pat: Avoid contention on cpa_lock if possible |
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Peter Zijlstra [mailto:a.p.zijlstra@chello.nl] wrote > On Wed, 2012-06-06 at 09:18 -0700, tip-bot for Shai Fultheim wrote: > > > [ I absolutely hate these locking patterns ... yet I have no better idea. Maybe the gents on Cc: ... ] > > Signed-off-by: Ingo Molnar <mingo@kernel.org> > > Oh yuck, this is vile.. > > static struct static_key scale_mp_trainwreck = STATIC_KEY_INIT_FALSE; > > static DEFINE_SPINLOCK(_cpa_lock); > > static inline void cpa_lock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > static inline void cpa_unlock(void) > { > if (static_key_false(&scale_mp_trainwreck)) > return; > > spin_lock(&_cpa_lock); > } > > And then use cpa_{,un}lock(), and the scale-mp guys can > static_key_slow_inc(&scale_mp_trainwreck). > > [ and yes I hate those jump_label names ... but I'm not wanting > to go through another round of bike-shed painting. ]
Looks pretty straight forward to do. We will try this route, as I'm concerned that synthetic CPUID bit will be kind of a global change for a pretty local consideration.
Comments?
(and we will also fix the other error pointed by Ingo - we are missing an include in this patch)
Regards, Shai.
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