Re: [PATCH RFC 3/4] Paravirtualized spinlock implementation for KVMguests

From: Jeremy Fitzhardinge
Date: Mon Aug 02 2010 - 11:20:11 EST

On 08/02/2010 01:48 AM, Avi Kivity wrote:
On 07/26/2010 09:15 AM, Srivatsa Vaddagiri wrote:
Paravirtual spinlock implementation for KVM guests, based heavily on Xen guest's
spinlock implementation.

+static struct spinlock_stats
+ u64 taken;
+ u32 taken_slow;
+ u64 released;
+#define HISTO_BUCKETS 30
+ u32 histo_spin_total[HISTO_BUCKETS+1];
+ u32 histo_spin_spinning[HISTO_BUCKETS+1];
+ u32 histo_spin_blocked[HISTO_BUCKETS+1];
+ u64 time_total;
+ u64 time_spinning;
+ u64 time_blocked;
+} spinlock_stats;

Could these be replaced by tracepoints when starting to spin/stopping spinning etc? Then userspace can reconstruct the histogram as well as see which locks are involved and what call paths.

Unfortunately not; the tracing code uses spinlocks.

(TBH I haven't actually tried, but I did give the code an eyeball to this end.)


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