| Message ID | ae90ece495d29f54fc9986a07f45ab6659136573.1589926004.git.anchalag@amazon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix PM hibernation in Xen guests | expand |
On 5/19/20 7:28 PM, Anchal Agarwal wrote: > From: Munehisa Kamata <kamatam@amazon.com> > > Currently, steal time accounting code in scheduler expects steal clock > callback to provide monotonically increasing value. If the accounting > code receives a smaller value than previous one, it uses a negative > value to calculate steal time and results in incorrectly updated idle > and steal time accounting. This breaks userspace tools which read > /proc/stat. > > top - 08:05:35 up 2:12, 3 users, load average: 0.00, 0.07, 0.23 > Tasks: 80 total, 1 running, 79 sleeping, 0 stopped, 0 zombie > Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,30100.0%id, 0.0%wa, 0.0%hi, 0.0%si,-1253874204672.0%st > > This can actually happen when a Xen PVHVM guest gets restored from > hibernation, because such a restored guest is just a fresh domain from > Xen perspective and the time information in runstate info starts over > from scratch. > > This patch introduces xen_save_steal_clock() which saves current values > in runstate info into per-cpu variables. Its couterpart, > xen_restore_steal_clock(), sets offset if it found the current values in > runstate info are smaller than previous ones. xen_steal_clock() is also > modified to use the offset to ensure that scheduler only sees > monotonically increasing number. > > Signed-off-by: Munehisa Kamata <kamatam@amazon.com> > Signed-off-by: Anchal Agarwal <anchalag@amazon.com> > --- > drivers/xen/time.c | 29 ++++++++++++++++++++++++++++- > include/xen/xen-ops.h | 2 ++ > 2 files changed, 30 insertions(+), 1 deletion(-) > > diff --git a/drivers/xen/time.c b/drivers/xen/time.c > index 0968859c29d0..3560222cc0dd 100644 > --- a/drivers/xen/time.c > +++ b/drivers/xen/time.c > @@ -23,6 +23,9 @@ static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate); > > static DEFINE_PER_CPU(u64[4], old_runstate_time); > > +static DEFINE_PER_CPU(u64, xen_prev_steal_clock); > +static DEFINE_PER_CPU(u64, xen_steal_clock_offset); Can you use old_runstate_time here? It is used to solve a similar problem for pv suspend, isn't it? -boris
diff --git a/drivers/xen/time.c b/drivers/xen/time.c index 0968859c29d0..3560222cc0dd 100644 --- a/drivers/xen/time.c +++ b/drivers/xen/time.c @@ -23,6 +23,9 @@ static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate); static DEFINE_PER_CPU(u64[4], old_runstate_time); +static DEFINE_PER_CPU(u64, xen_prev_steal_clock); +static DEFINE_PER_CPU(u64, xen_steal_clock_offset); + /* return an consistent snapshot of 64-bit time/counter value */ static u64 get64(const u64 *p) { @@ -149,7 +152,7 @@ bool xen_vcpu_stolen(int vcpu) return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable; } -u64 xen_steal_clock(int cpu) +static u64 __xen_steal_clock(int cpu) { struct vcpu_runstate_info state; @@ -157,6 +160,30 @@ u64 xen_steal_clock(int cpu) return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; } +u64 xen_steal_clock(int cpu) +{ + return __xen_steal_clock(cpu) + per_cpu(xen_steal_clock_offset, cpu); +} + +void xen_save_steal_clock(int cpu) +{ + per_cpu(xen_prev_steal_clock, cpu) = xen_steal_clock(cpu); +} + +void xen_restore_steal_clock(int cpu) +{ + u64 steal_clock = __xen_steal_clock(cpu); + + if (per_cpu(xen_prev_steal_clock, cpu) > steal_clock) { + /* Need to update the offset */ + per_cpu(xen_steal_clock_offset, cpu) = + per_cpu(xen_prev_steal_clock, cpu) - steal_clock; + } else { + /* Avoid unnecessary steal clock warp */ + per_cpu(xen_steal_clock_offset, cpu) = 0; + } +} + void xen_setup_runstate_info(int cpu) { struct vcpu_register_runstate_memory_area area; diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h index 89b1e88712d6..74fb5eb3aad8 100644 --- a/include/xen/xen-ops.h +++ b/include/xen/xen-ops.h @@ -37,6 +37,8 @@ void xen_time_setup_guest(void); void xen_manage_runstate_time(int action); void xen_get_runstate_snapshot(struct vcpu_runstate_info *res); u64 xen_steal_clock(int cpu); +void xen_save_steal_clock(int cpu); +void xen_restore_steal_clock(int cpu); int xen_setup_shutdown_event(void);