search for: config_paravirt_qspinlocks_lit

On Tue, Jul 07, 2020 at 11:33:45PM -0400, Waiman Long wrote: > From 5d7941a498935fb225b2c7a3108cbf590114c3db Mon Sep 17 00:00:00 2001 > From: Waiman Long <longman at redhat.com> > Date: Tue, 7 Jul 2020 22:29:16 -0400 > Subject: [PATCH 2/9] locking/pvqspinlock: Introduce > CONFIG_PARAVIRT_QSPINLOCKS_LITE > > Add a new PARAVIRT_QSPINLOCKS_LITE config option that allows > architectures to use the PV qspinlock code without the need to use or > implement a pv_kick() function, thus eliminating the atomic unlock > overhead. The non-atomic queued_spin_unlock() can be used instead. > Th...

...nd the wait is not so accurate. I think perhaps we could change things so we wait on the correct CPU when queued, which might be good enough (we could also put the lock owner CPU in the spinlock word, if we add another format). > Attached are two > additional qspinlock patches that adds a CONFIG_PARAVIRT_QSPINLOCKS_LITE > option to not require pv_kick(). There is also a fixup patch to be > applied after your patchset. > > I don't have access to a PPC LPAR with shared processor at the moment, > so I can't test the performance of the paravirt code. Would you mind > adding my patches a...

...nd the wait is not so accurate. I think perhaps we could change things so we wait on the correct CPU when queued, which might be good enough (we could also put the lock owner CPU in the spinlock word, if we add another format). > Attached are two > additional qspinlock patches that adds a CONFIG_PARAVIRT_QSPINLOCKS_LITE > option to not require pv_kick(). There is also a fixup patch to be > applied after your patchset. > > I don't have access to a PPC LPAR with shared processor at the moment, > so I can't test the performance of the paravirt code. Would you mind > adding my patches a...

Excerpts from Waiman Long's message of July 7, 2020 4:39 am: > On 7/6/20 12:35 AM, Nicholas Piggin wrote: >> v3 is updated to use __pv_queued_spin_unlock, noticed by Waiman (thank you). >> >> Thanks, >> Nick >> >> Nicholas Piggin (6): >> powerpc/powernv: must include hvcall.h to get PAPR defines >> powerpc/pseries: move some PAPR

Excerpts from Waiman Long's message of July 7, 2020 4:39 am: > On 7/6/20 12:35 AM, Nicholas Piggin wrote: >> v3 is updated to use __pv_queued_spin_unlock, noticed by Waiman (thank you). >> >> Thanks, >> Nick >> >> Nicholas Piggin (6): >> powerpc/powernv: must include hvcall.h to get PAPR defines >> powerpc/pseries: move some PAPR

...if this is actually the cause of the slowdown yet. Regarding the paravirt lock, I have taken a further look into the current PPC spinlock code. There is an equivalent of pv_wait() but no pv_kick(). Maybe PPC doesn't really need that. Attached are two additional qspinlock patches that adds a CONFIG_PARAVIRT_QSPINLOCKS_LITE option to not require pv_kick(). There is also a fixup patch to be applied after your patchset. I don't have access to a PPC LPAR with shared processor at the moment, so I can't test the performance of the paravirt code. Would you mind adding my patches and do some performance test on...

...an 255 cpus, we can put the (cpu_nr + 1) into the lock byte. The special 0xff value can be used to indicate a cpu number >= 255 for indirect yield. The required change to the qspinlock code will be minimal, I think. >> Attached are two >> additional qspinlock patches that adds a CONFIG_PARAVIRT_QSPINLOCKS_LITE >> option to not require pv_kick(). There is also a fixup patch to be >> applied after your patchset. >> >> I don't have access to a PPC LPAR with shared processor at the moment, >> so I can't test the performance of the paravirt code. Would you mind >>...