From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Feng Wu <feng.wu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>,
George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
xen-devel@lists.xen.org, Jan Beulich <jbeulich@suse.com>
Subject: Ideas Re: [PATCH v14 1/2] vmx: VT-d posted-interrupt core logic handling
Date: Fri, 4 Mar 2016 17:00:31 -0500 [thread overview]
Message-ID: <20160304220031.GA28111@char.us.oracle.com> (raw)
In-Reply-To: <1456714816-3876-2-git-send-email-feng.wu@intel.com>
> +/* Handle VT-d posted-interrupt when VCPU is blocked. */
> +static void pi_wakeup_interrupt(struct cpu_user_regs *regs)
> +{
> + struct arch_vmx_struct *vmx, *tmp;
> + spinlock_t *lock = &per_cpu(vmx_pi_blocking, smp_processor_id()).lock;
> + struct list_head *blocked_vcpus =
> + &per_cpu(vmx_pi_blocking, smp_processor_id()).list;
> +
> + ack_APIC_irq();
> + this_cpu(irq_count)++;
> +
> + spin_lock(lock);
> +
> + /*
> + * XXX: The length of the list depends on how many vCPU is current
> + * blocked on this specific pCPU. This may hurt the interrupt latency
> + * if the list grows to too many entries.
> + */
> + list_for_each_entry_safe(vmx, tmp, blocked_vcpus, pi_blocking.list)
> + {
My recollection of the 'most-horrible' case of this being really bad is when
the scheduler puts the vCPU0 and VCPU1 of the guest on the same pCPU (as an example)
and they round-robin all the time.
<handwaving>
Would it be perhaps possible to have an anti-affinity flag to deter the
scheduler from this? That is whichever struct vcpu has 'anti-affinity' flag
set - the scheduler will try as much as it can _to not_ schedule the 'struct vcpu'
if the previous 'struct vcpu' had this flag as well on this pCPU?
And then try to schedule 'normal' guests.
[I am ignoring the toolstack plumbing for this and so on]
My naive thinking is that while it may result in a lot of a guest vCPU
moving around (as the prev 'struct vcpu' would disallow this new vCPU to run
on a CPU that already has this type of guest) it would 'spread' out the guests
with 'anti-affinity' flag across all the pCPUS.
It would suck for over-subscriptions but <handwaving>.
And maybe this enforcment need not been so strict. Perhaps it can allow
one 'prev' of an 'struct vpu' which has this flag enabled but not more than
two?
</handwaving>
/me goes off to the pub.
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next prev parent reply other threads:[~2016-03-04 22:00 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 3:00 [PATCH v14 0/2] Add VT-d Posted-Interrupts support Feng Wu
2016-02-29 3:00 ` [PATCH v14 1/2] vmx: VT-d posted-interrupt core logic handling Feng Wu
2016-02-29 13:33 ` Jan Beulich
2016-02-29 13:52 ` Dario Faggioli
2016-03-01 5:39 ` Wu, Feng
2016-03-01 9:24 ` Jan Beulich
2016-03-01 10:16 ` George Dunlap
2016-03-01 13:06 ` Wu, Feng
2016-03-01 5:24 ` Tian, Kevin
2016-03-01 5:39 ` Wu, Feng
2016-03-04 22:00 ` Konrad Rzeszutek Wilk [this message]
2016-03-07 11:21 ` Ideas " George Dunlap
2016-03-07 15:53 ` Konrad Rzeszutek Wilk
2016-03-07 16:19 ` Dario Faggioli
2016-03-07 20:23 ` Konrad Rzeszutek Wilk
2016-03-08 12:02 ` George Dunlap
2016-03-08 13:10 ` Wu, Feng
2016-03-08 14:42 ` George Dunlap
2016-03-08 15:42 ` Jan Beulich
2016-03-08 17:05 ` George Dunlap
2016-03-08 17:26 ` Jan Beulich
2016-03-08 18:38 ` George Dunlap
2016-03-09 5:06 ` Wu, Feng
2016-03-09 13:39 ` Jan Beulich
2016-03-09 16:01 ` George Dunlap
2016-03-09 16:31 ` Jan Beulich
2016-03-09 16:23 ` On setting clear criteria for declaring a feature acceptable (was "vmx: VT-d posted-interrupt core logic handling") George Dunlap
2016-03-09 16:58 ` On setting clear criteria for declaring a feature acceptable Jan Beulich
2016-03-09 18:02 ` On setting clear criteria for declaring a feature acceptable (was "vmx: VT-d posted-interrupt core logic handling") David Vrabel
2016-03-10 1:15 ` Wu, Feng
2016-03-10 9:30 ` George Dunlap
2016-03-10 5:09 ` Tian, Kevin
2016-03-10 8:07 ` vmx: VT-d posted-interrupt core logic handling Jan Beulich
2016-03-10 8:43 ` Tian, Kevin
2016-03-10 9:05 ` Jan Beulich
2016-03-10 9:20 ` Tian, Kevin
2016-03-10 10:05 ` Tian, Kevin
2016-03-10 10:18 ` Jan Beulich
2016-03-10 10:35 ` David Vrabel
2016-03-10 10:46 ` George Dunlap
2016-03-10 11:16 ` David Vrabel
2016-03-10 11:49 ` George Dunlap
2016-03-10 13:24 ` Jan Beulich
2016-03-10 11:00 ` George Dunlap
2016-03-10 11:21 ` Dario Faggioli
2016-03-10 13:36 ` Wu, Feng
2016-05-17 13:27 ` Konrad Rzeszutek Wilk
2016-05-19 7:22 ` Wu, Feng
2016-03-10 10:41 ` George Dunlap
2016-03-09 5:22 ` Ideas Re: [PATCH v14 1/2] " Wu, Feng
2016-03-09 11:25 ` George Dunlap
2016-03-09 12:06 ` Wu, Feng
2016-02-29 3:00 ` [PATCH v14 2/2] Add a command line parameter for VT-d posted-interrupts Feng Wu
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