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xen-ia64-devel
Re: [Xen-ia64-devel] [PATCH] pal_halt_light emulatefor domU TAKE3
Hi Anthony
Thank you for your comment,
I am already trying test in both cases(for more than 16Hour 4CPU).
But I select current by code simplicity.
I agree your point, I will fix it.
Thanks
Atsushi SAKAI
>Hi SAKAI,
>
>Good effort,
>I have one small comment
>+ vcpu_get_next_timer_ns=cycle_to_ns(local_cpu_data->itm_next);
>
>If the itm_next is large enough (it can be), cycle_to_ns may overflow,
>maybe following statement is better.
>vcpu_get_next_timer_ns=cycle_to_ns(local_cpu_data->itm_delta)+NOW;
>
>
>-Anthony
>
>
>>-----Original Message-----
>>From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Atsushi
>>SAKAI
>>Sent: 2006?8?21? 19:39
>>To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>>Subject: [Xen-ia64-devel] [PATCH] pal_halt_light emulatefor domU TAKE3
>>
>>This is a pal_halt_light emulation for domU TAKE3.
>>
>>Status
>>
>>I tested and passed 16h 4CPU DomUx2 continuous Linux Kernel Compile
>>using this patch.
>>To pass above test, I mainly changed 2 points(from previous TAKE2).
>>If I test Previous TAKE2 with same configuration,
>>DomU make a memory leak after 2-3 hours running.
>>
>>
>>Changes from Previous Take2 (2points):
>>
>>1)for set_timer/do_block correctness(for vcpu_migration case)
>> it add timer migrates for vcpu migrates
>>
>> Add migrate timer for hlt_timer_fn in context_switch.
>>
>>2)for VIRQ_ITC behavior correctness(for vcpu_migration case)
>> Change the order of
>> send_guest_vcpu_virq(vcpu, VIRQ_ITC)
>> AND
>> PSCBX(vcpu, domain_itm_last) = PSCBX(vcpu, domain_itm)
>> in vcpu_pend_timer
>>
>>These changes affects only for domU/0.
>>
>>
>>Reason for changes.
>>1)Previous TAKE2 Patch it is not included migrate timer.
>> The hlt_timer should be in same pcpu as vcpu allocated.
>>
>>
>>2)The VIRQ_ITC cycle is destroyed
>> in case vcpu migration occurred when vcpu_pend_timer runs (called by
>>hlt_timer_fn)
>>
>> The VIRQ_ITC cycle is (simple writing)
>> ia64_get_itc reaches domain_itm at Xen.
>> send VIRQ_ITC to GuestOS
>> GuestOS handles and set next itm by hypercall to Xen
>> Repeats.
>>
>>
>> Currently, the function order in vcpu_pend_timer is
>> a)send VIRQ_ITC(vcpu_pend_timer)
>> b)then stamp the signal send information.(update domain_itm_last)
>> In this configuration,
>> domain_itm_last update time and hypercall set itm(which comes from VIRQ_ITC)
>> is important.
>>
>> This order is problematic in case vcpu_migration occurred as follows
>> (following event occures nearly 1-2 hour running
>> by 2xDomU 3vcpu(total 6vcpu for domU) in 4pcpu Linux Kernel Compile test)
>>
>> vcpu_pend_timer@A is started.(GuestOS is not running at this moment)
>> interrupts@B
>> vcpu_pend_timer@A is paused
>> Credit Scheduler steal vcpu from A to B
>> vcpu_pend_timer@B is started and ended
>>
>> ******The following process should be after vcpu_pend_timer*****
>> domain_itm is set by GuestOS hypercall. and domain_itm updated.
>>
>> vcpu_pend_timer@A is resumed. but domain_itm is already updated.
>>
>>
>> To avoid this, order should be exchanged b) a)
>> After this fixation, we are free from timing consideration of
>> VIRQ_ITC cycle and domain_itm_last update time.
>> (domain_itm_last update should be before the hypercall set itm)
>>
>>Comments for TIMER_SLOP
>>
>> The Anthony suggested parameter (TIMER_SLOP) is not used in x86.
>>So I am not used.
>>
>>Comments for Note(for 2)
>>
>> After Yamahata's report(domU hung), I tested many times.
>>Every time, Just memory error(oom-killer) on DomU is detected(not hunged).
>>So I try to solve this problem,
>>Some body suggests me this kind of error occurred in case
>>CPU is running but Timer is stopped
>>
>>Because RCU(Read Copy Update) in Linux garbage collection occurred by timer.
>>But memory allocation continues during CPU running.
>>(it makes oom-killer running state.)
>>
>>I checked the behavior of vcpu and timer and found the timing problem in
>>vcpu_pend_timer.
>>
>>References for this modification
>>(for 2)
>>about RCU(Read Copy Update)
>>http://en.wikipedia.org/wiki/Read-copy-update
>>
>>(Other fixes)
>>Yamahata's for VTI migrate timer.
>>http://lists.xensource.com/archives/html/xen-ia64-devel/2006-07/msg00375.ht
>>ml
>>stop_timer
>>http://lists.xensource.com/archives/html/xen-ia64-devel/2006-07/msg00171.ht
>>ml
>>
>>
>>Signed-off-by: Atsushi SAKAI <sakaia@xxxxxxxxxxxxxx>
>>
>>
>>
>>
>>
>>
>>
>
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