| Message ID | 20240722121643.18116-4-jgross@suse.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Mini-OS: tidy up arch/x86/time.c | expand |
Juergen Gross, le lun. 22 juil. 2024 14:16:43 +0200, a ecrit: > monotonic_clock() in arch/x86/time.c is more complex than needed: it > has basically two nested loops making sure the time data obtained from > Xen are valid. > > Simplify that by merging some of the used sub-functions into the main > function and using only a single loop. Further simplify the code by > using struct vcpu_time_info for the local instance instead of defining > a similar structure in the code. > > Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org> > --- > arch/x86/time.c | 58 ++++++++++++++----------------------------------- > 1 file changed, 16 insertions(+), 42 deletions(-) > > diff --git a/arch/x86/time.c b/arch/x86/time.c > index 7fd7abef..52916e15 100644 > --- a/arch/x86/time.c > +++ b/arch/x86/time.c > @@ -44,24 +44,10 @@ > *************************************************************************/ > > /* These are peridically updated in shared_info, and then copied here. */ > -struct shadow_time_info { > - uint64_t tsc_timestamp; /* TSC at last update of time vals. */ > - uint64_t system_timestamp; /* Time, in nanosecs, since boot. */ > - uint32_t tsc_to_nsec_mul; > - int tsc_shift; > - uint32_t version; > -}; > static struct timespec shadow_ts; > static uint32_t shadow_ts_version; > > -static struct shadow_time_info shadow; > - > -static inline int time_values_up_to_date(void) > -{ > - struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; > - > - return shadow.version == src->version; > -} > +static struct vcpu_time_info shadow; > > static inline int wc_values_up_to_date(void) > { > @@ -113,22 +99,7 @@ static unsigned long get_nsec_offset(void) > rdtscll(now); > delta = now - shadow.tsc_timestamp; > > - return scale_delta(delta, shadow.tsc_to_nsec_mul, shadow.tsc_shift); > -} > - > -static void get_time_values_from_xen(void) > -{ > - struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; > - > - do { > - shadow.version = src->version; > - rmb(); > - shadow.tsc_timestamp = src->tsc_timestamp; > - shadow.system_timestamp = src->system_time; > - shadow.tsc_to_nsec_mul = src->tsc_to_system_mul; > - shadow.tsc_shift = src->tsc_shift; > - rmb(); > - } while ( (src->version & 1) | (shadow.version ^ src->version) ); > + return scale_delta(delta, shadow.tsc_to_system_mul, shadow.tsc_shift); > } > > /* > @@ -138,19 +109,22 @@ static void get_time_values_from_xen(void) > */ > uint64_t monotonic_clock(void) > { > - uint64_t time; > - uint32_t local_time_version; > + struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; > > - do { > - local_time_version = shadow.version; > - rmb(); > - time = shadow.system_timestamp + get_nsec_offset(); > - if ( !time_values_up_to_date() ) > - get_time_values_from_xen(); > - rmb(); > - } while ( local_time_version != shadow.version ); > + if ( shadow.version != src->version ) > + { > + do { > + shadow.version = src->version; > + rmb(); > + shadow.tsc_timestamp = src->tsc_timestamp; > + shadow.system_time = src->system_time; > + shadow.tsc_to_system_mul = src->tsc_to_system_mul; > + shadow.tsc_shift = src->tsc_shift; > + rmb(); > + } while ( (src->version & 1) || (shadow.version != src->version) ); > + } > > - return time; > + return shadow.system_time + get_nsec_offset(); > } > > static void update_wallclock(void) > -- > 2.43.0 >
diff --git a/arch/x86/time.c b/arch/x86/time.c index 7fd7abef..52916e15 100644 --- a/arch/x86/time.c +++ b/arch/x86/time.c @@ -44,24 +44,10 @@ *************************************************************************/ /* These are peridically updated in shared_info, and then copied here. */ -struct shadow_time_info { - uint64_t tsc_timestamp; /* TSC at last update of time vals. */ - uint64_t system_timestamp; /* Time, in nanosecs, since boot. */ - uint32_t tsc_to_nsec_mul; - int tsc_shift; - uint32_t version; -}; static struct timespec shadow_ts; static uint32_t shadow_ts_version; -static struct shadow_time_info shadow; - -static inline int time_values_up_to_date(void) -{ - struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; - - return shadow.version == src->version; -} +static struct vcpu_time_info shadow; static inline int wc_values_up_to_date(void) { @@ -113,22 +99,7 @@ static unsigned long get_nsec_offset(void) rdtscll(now); delta = now - shadow.tsc_timestamp; - return scale_delta(delta, shadow.tsc_to_nsec_mul, shadow.tsc_shift); -} - -static void get_time_values_from_xen(void) -{ - struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; - - do { - shadow.version = src->version; - rmb(); - shadow.tsc_timestamp = src->tsc_timestamp; - shadow.system_timestamp = src->system_time; - shadow.tsc_to_nsec_mul = src->tsc_to_system_mul; - shadow.tsc_shift = src->tsc_shift; - rmb(); - } while ( (src->version & 1) | (shadow.version ^ src->version) ); + return scale_delta(delta, shadow.tsc_to_system_mul, shadow.tsc_shift); } /* @@ -138,19 +109,22 @@ static void get_time_values_from_xen(void) */ uint64_t monotonic_clock(void) { - uint64_t time; - uint32_t local_time_version; + struct vcpu_time_info *src = &HYPERVISOR_shared_info->vcpu_info[0].time; - do { - local_time_version = shadow.version; - rmb(); - time = shadow.system_timestamp + get_nsec_offset(); - if ( !time_values_up_to_date() ) - get_time_values_from_xen(); - rmb(); - } while ( local_time_version != shadow.version ); + if ( shadow.version != src->version ) + { + do { + shadow.version = src->version; + rmb(); + shadow.tsc_timestamp = src->tsc_timestamp; + shadow.system_time = src->system_time; + shadow.tsc_to_system_mul = src->tsc_to_system_mul; + shadow.tsc_shift = src->tsc_shift; + rmb(); + } while ( (src->version & 1) || (shadow.version != src->version) ); + } - return time; + return shadow.system_time + get_nsec_offset(); } static void update_wallclock(void)
monotonic_clock() in arch/x86/time.c is more complex than needed: it has basically two nested loops making sure the time data obtained from Xen are valid. Simplify that by merging some of the used sub-functions into the main function and using only a single loop. Further simplify the code by using struct vcpu_time_info for the local instance instead of defining a similar structure in the code. Signed-off-by: Juergen Gross <jgross@suse.com> --- arch/x86/time.c | 58 ++++++++++++++----------------------------------- 1 file changed, 16 insertions(+), 42 deletions(-)