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Re: [Qemu-devel] [RFC PATCH v8 11/21] replay: recording and replaying cl
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC PATCH v8 11/21] replay: recording and replaying clock ticks |
Date: |
Tue, 03 Feb 2015 12:04:57 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 03/02/2015 11:51, Pavel Dovgaluk wrote:
>> From: Paolo Bonzini [mailto:address@hidden
>> On 22/01/2015 09:52, Pavel Dovgalyuk wrote:
>>> Clock ticks are considered as the sources of non-deterministic data for
>>> virtual machine. This patch implements saving the clock values when they
>>> are acquired (virtual, host clock, rdtsc, and some other timers).
>>> When replaying the execution corresponding values are read from log and
>>> transfered to the module, which wants to read the values.
>>> Such a design required the clock polling to be synchronized. Sometimes
>>> it is not true - e.g. when timeouts for timer lists are checked. In this
>>> case
>>> we use a cached value of the clock, passing it to the client code.
>>>
>>> Signed-off-by: Pavel Dovgalyuk <address@hidden>
>>> ---
>>> cpus.c | 3 +-
>>> include/qemu/timer.h | 10 +++++
>>> qemu-timer.c | 7 ++--
>>> replay/Makefile.objs | 1 +
>>> replay/replay-internal.h | 13 +++++++
>>> replay/replay-time.c | 84
>>> ++++++++++++++++++++++++++++++++++++++++++++++
>>> replay/replay.h | 25 ++++++++++++++
>>> stubs/replay.c | 9 +++++
>>> 8 files changed, 147 insertions(+), 5 deletions(-)
>>> create mode 100755 replay/replay-time.c
>>>
>>> diff --git a/cpus.c b/cpus.c
>>> index 8787277..01d89aa 100644
>>> --- a/cpus.c
>>> +++ b/cpus.c
>>> @@ -353,7 +353,8 @@ static void icount_warp_rt(void *opaque)
>>>
>>> seqlock_write_lock(&timers_state.vm_clock_seqlock);
>>> if (runstate_is_running()) {
>>> - int64_t clock = cpu_get_clock_locked();
>>> + int64_t clock = REPLAY_CLOCK(REPLAY_CLOCK_VIRTUAL_RT,
>>> + cpu_get_clock_locked());
>>> int64_t warp_delta;
>>>
>>> warp_delta = clock - vm_clock_warp_start;
>>> diff --git a/include/qemu/timer.h b/include/qemu/timer.h
>>> index 0666920..0c2472c 100644
>>> --- a/include/qemu/timer.h
>>> +++ b/include/qemu/timer.h
>>> @@ -4,6 +4,7 @@
>>> #include "qemu/typedefs.h"
>>> #include "qemu-common.h"
>>> #include "qemu/notify.h"
>>> +#include "replay/replay.h"
>>>
>>> /* timers */
>>>
>>> @@ -760,6 +761,8 @@ int64_t cpu_icount_to_ns(int64_t icount);
>>> /*******************************************/
>>> /* host CPU ticks (if available) */
>>>
>>> +#define cpu_get_real_ticks cpu_get_real_ticks_impl
>>> +
>>> #if defined(_ARCH_PPC)
>>>
>>> static inline int64_t cpu_get_real_ticks(void)
>>> @@ -913,6 +916,13 @@ static inline int64_t cpu_get_real_ticks (void)
>>> }
>>> #endif
>>>
>>> +#undef cpu_get_real_ticks
>>> +
>>> +static inline int64_t cpu_get_real_ticks(void)
>>
>> cpu_get_real_ticks should never be used. Please instead wrap
>> cpu_get_ticks() with REPLAY_CLOCK.
>
> I don't quite understand this comment.
> Do you mean that I should move REPLAY_CLOCK to the cpu_get_real_ticks usages
> instead of it's implementation?
Only to the cpu_get_ticks usage. The others are okay.
>>> +/*! Reads next clock value from the file.
>>> + If clock kind read from the file is different from the parameter,
>>> + the value is not used.
>>> + If the parameter is -1, the clock value is read to the cache anyway. */
>>
>> In what case could the clock kind not match?
>>
>
> It was used in full version which had to skip clock from the log while
> loading the VM state.
So can it be removed for now?
Paolo
>>
>>> +void replay_read_next_clock(unsigned int kind);
>>> +
>>> /* Asynchronous events queue */
>>>
>
>
> Pavel Dovgalyuk
>