From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm <kvm@vger.kernel.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Eric Northup <digitaleric@google.com>
Subject: Re: [PATCH v4] KVM: Introduce direct MSI message injection for in-kernel irqchips
Date: Wed, 04 Apr 2012 11:47:04 +0300 [thread overview]
Message-ID: <4F7C0A88.2000902@redhat.com> (raw)
In-Reply-To: <4F7B3243.7050803@siemens.com>
On 04/03/2012 08:24 PM, Jan Kiszka wrote:
> >
> >>>
> >>> A performance note: delivering an interrupt needs to search all vcpus
> >>> for an APIC ID match. The previous plan was to cache (or pre-calculate)
> >>> this lookup in the irq routing table. Now it looks like we'll need a
> >>> separate cache for this.
> >>
> >> As this is non-existent until today, we don't regress here. And it can
> >> still be added on top later on, transparently.
> >
> > Yes, it's just a note, not an objection. The cache lookup will be
> > slower than the gsi lookup (hash table vs. array) but still O(1) vs. the
> > current O(n).
>
> If you are concerned about performance in this path, wouldn't a DMA
> interface for MSI injection be counterproductive?
Yes, it would. The lack of coalescing reporting support is also
problematic. I just mentioned this idea as food for thought.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2012-04-04 8:47 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-28 17:47 [PATCH v2] KVM: Introduce direct MSI message injection for in-kernel irqchips Jan Kiszka
2012-03-28 17:52 ` Jan Kiszka
2012-03-28 19:58 ` Eric Northup
2012-03-28 20:21 ` Jan Kiszka
2012-03-29 15:39 ` Michael S. Tsirkin
2012-03-29 15:43 ` Jan Kiszka
2012-03-29 16:15 ` [PATCH v3] " Jan Kiszka
2012-03-29 16:46 ` Michael S. Tsirkin
2012-03-29 16:50 ` Jan Kiszka
2012-03-29 18:25 ` Jan Kiszka
2012-03-29 19:14 ` [PATCH v4] " Jan Kiszka
2012-03-29 19:41 ` Michael S. Tsirkin
2012-03-30 7:45 ` Jan Kiszka
2012-03-30 12:45 ` Michael S. Tsirkin
2012-04-03 16:27 ` Avi Kivity
2012-04-03 16:47 ` Jan Kiszka
2012-04-03 16:54 ` Avi Kivity
2012-04-03 17:24 ` Jan Kiszka
2012-04-04 8:47 ` Avi Kivity [this message]
2012-04-04 8:38 ` Michael S. Tsirkin
2012-04-04 8:44 ` Avi Kivity
2012-04-04 8:53 ` Michael S. Tsirkin
2012-04-04 9:22 ` Jan Kiszka
2012-04-04 9:36 ` Avi Kivity
2012-04-04 9:38 ` Jan Kiszka
2012-04-04 9:55 ` Avi Kivity
2012-04-04 10:48 ` Jan Kiszka
2012-04-04 11:50 ` Avi Kivity
2012-04-04 12:01 ` Jan Kiszka
2012-04-10 18:30 ` [PATCH] KVM: Introduce generic interrupt " Jan Kiszka
2012-04-23 14:44 ` Jan Kiszka
2012-04-23 15:17 ` Avi Kivity
2012-04-23 15:32 ` Avi Kivity
2012-04-23 15:55 ` Jan Kiszka
2012-04-24 11:54 ` Avi Kivity
2012-04-24 11:57 ` [PATCH v4] KVM: Introduce direct MSI message " Avi Kivity
2012-04-24 12:07 ` Jan Kiszka
2012-04-24 12:59 ` Avi Kivity
2012-04-24 13:24 ` Jan Kiszka
2012-04-11 22:10 ` [PATCH v3] " Marcelo Tosatti
2012-04-12 9:28 ` Jan Kiszka
2012-04-12 22:38 ` Marcelo Tosatti
2012-04-13 13:45 ` Jan Kiszka
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