On 08/02/2010 06:20 PM, Jeremy Fitzhardinge wrote:
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.)
Hm. The tracing code already uses a specialized lock (arch_spinlock_t),
perhaps we can make this lock avoid the tracing?
It's really sad, btw, there's all those nice lockless ring buffers and
then a spinlock for ftrace_vbprintk(), instead of a per-cpu buffer.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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