On Thu, Jul 17, 2014 at 01:19:57PM +1000, Stewart Smith wrote:
> The POWER8 processor has a Micro Partition Prefetch Engine, which is
> a fancy way of saying "has way to store and load contents of L2 or
> L2+MRU way of L3 cache". We initiate the storing of the log (list of
> addresses) using the logmpp instruction and start restore by writing
> to a SPR.
>
> The logmpp instruction takes parameters in a single 64bit register:
> - starting address of the table to store log of L2/L2+L3 cache contents
> - 32kb for L2
> - 128kb for L2+L3
> - Aligned relative to maximum size of the table (32kb or 128kb)
> - Log control (no-op, L2 only, L2 and L3, abort logout)
>
> We should abort any ongoing logging before initiating one.
Do we ever want to wait for ongoing logging to finish?
[snip]
> +#if defined(CONFIG_PPC_64K_PAGES)
> +#define MPP_BUFFER_ORDER 0
> +#elif defined(CONFIG_PPC_4K_PAGES)
> +#define MPP_BUFFER_ORDER 4
Why 4 not 3? You only need 32kB, don't you?
> +static struct kvmppc_vcore *kvmppc_vcore_create(struct kvm *kvm, int core)
> +{
> + struct kvmppc_vcore *vcore;
> +
> + vcore = kzalloc(sizeof(struct kvmppc_vcore), GFP_KERNEL);
> +
> + if (vcore == NULL)
> + return NULL;
> +
> + INIT_LIST_HEAD(&vcore->runnable_threads);
> + spin_lock_init(&vcore->lock);
> + init_waitqueue_head(&vcore->wq);
> + vcore->preempt_tb = TB_NIL;
> + vcore->lpcr = kvm->arch.lpcr;
> + vcore->first_vcpuid = core * threads_per_core;
> + vcore->kvm = kvm;
Is there a particular reason why you need to pull this code out into a
separate function? If so, it would be a little nicer if you did that
in a separate patch, to make it easier to see that the code motion
changes nothing.
> @@ -1590,9 +1645,16 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
>
> srcu_idx = srcu_read_lock(&vc->kvm->srcu);
>
> + if (vc->mpp_buffer_is_valid)
> + ppc_start_restoring_l2_cache(vc);
> +
> __kvmppc_vcore_entry();
>
> spin_lock(&vc->lock);
> +
> + if (vc->mpp_buffer)
> + ppc_start_saving_l2_cache(vc);
I wonder if we would get better performance improvements if we kicked
this off earlier, for instance before we save all the FP/VSX state and
switch the MMU? I guess that could be a subsequent patch.
Paul.
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