Re: [Xen-devel] [PATCH 0/5] RTC: New logic to emulate RTC

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Sorry, due to the bad outlook auto format. The patch format is wrong.:(
Will resend it under linux.

best regards
yang


> -----Original Message-----
> From: Zhang, Yang Z
> Sent: Thursday, March 08, 2012 8:42 AM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [PATCH 0/5] RTC: New logic to emulate RTC
> 
> RESEND:
> Correct a typo in comments.
> 
> Current RTC emulation uses periodic timer(2 per second) to emulate RTC clock
> update. And it will stop CPU staying at deep C-state for long period even when
> guest is idle. Our experience shows the Pkg C6 residency reduced 6% when
> running 64 idle guest due to the two periodic timers. After investigation, I 
> found
> the two periodic timer is used to update RTC clock, check update-ended and
> check alarm. The following patch achieves the same goal w/o always running the
> periodic timer.
> For rtc clock:  the per domain variable time_offset_seconds is used to record
> the offset between the domain and wall clock. So we can get the domain rtc
> directly by calculating time_offset_seconds with wall clock.
> For update-ended check: use a timer to emulate it , and the timer runs only
> when the last update-ended interrupt flag(UF) is cleared. If the UF already 
> set,
> there is no need to set it again.
> For alarm check: also use a timer to emulate it, and the timer runs only when 
> the
> flag of alarm interrupt enable bit is set.
> 
> The logic is a little different between the update-ended check and alarm 
> check.
> For update-ended check ,we use UF(update-ended flag) as the judgment and
> use AIE(alarm interrupt enable flag) for alarm check. This is because OS may 
> poll
> the UF bit to check whether the update cycle is finished.(UF bit change from 
> 0 to
> 1 means the update cycle ended). So we need to run the timer when UF bit is
> cleared.
> ---
> Yang Zhang (5):
>       RTC: use offset to caculatet rtc clock
>       RTC: fix 12-hour mode
>       RTC: Add UIP(update in progress) check logic
>       RTC: Add RTC update-ended interrupt support
>       RTC: Add alarm support
> 
> best regards
> yang

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