
C5 Instances for EC2 Now Available - jeffbarr
https://aws.amazon.com/blogs/aws/now-available-compute-intensive-c5-instances-for-amazon-ec2/
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pquerna
Intertwined with this announcement of an new instance type, is that it uses a
non-Xen hypervisor.

Has anyone booted one yet? Is it KVM or something from scratch that AWS wrote?

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nnx
What’s the benefit of KVM over Xen these days?

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abdulla
KVM can take better advantage of hardware acceleration than Xen. Xen requires
a modified guest, which traps back to the host more frequently.

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wmf
Is that true with the newer modes?
[https://wiki.xen.org/wiki/Understanding_the_Virtualization_S...](https://wiki.xen.org/wiki/Understanding_the_Virtualization_Spectrum)

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abdulla
This is based on a cursory examination of [1], so I may be off-base. But Xen
appears to rely on the host for many things that can be, and often are,
hardware accelerated in KVM. Searching for CONFIG_XEN_PVHVM, it doesn't appear
to cover much.

[1]
[https://github.com/torvalds/linux/blob/master/arch/x86/xen/](https://github.com/torvalds/linux/blob/master/arch/x86/xen/)

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jotto
No pricing info on c5 or whether c4 has changed in either the blog post or
[https://aws.amazon.com/ec2/pricing/on-
demand](https://aws.amazon.com/ec2/pricing/on-demand)

~~~
joemag
The pricing is out: [https://aws.amazon.com/ec2/pricing/on-
demand/](https://aws.amazon.com/ec2/pricing/on-demand/)

Note, that you will need to select Northern Virginia, Oregon or Ireland to see
C5 prices. By default (at least for me) the pricing page loads Ohio, which
doesn't have C5 yet.

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matt_wulfeck
Really happy to see even small versions of these instances having large NICs.

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wmf
Interesting that Amazon is charging less for Skylake than Broadwell while the
list prices for Skylake are higher. I guess Intel really wants you to move to
the cloud.

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ac29
Skylake should be more energy efficient and denser (cores/rack) than
Broadwell, so it makes sense for them to be cheaper.

Also, I wouldn't assume Amazon pays anything close to list price, or even
necessarily runs publicly announced parts.

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CaliforniaKarl
I'm a little bit surprised that Amazon are mapping vCPUs to HyperThreads,
instead of to cores. It seems to me like, if this is targeted at compute-
intensive workloads, that it may be overcommitting a bit. Or is there recent
research saying that an HT thread is equivalent to a core for compute-
intensive workloads?

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tedivm
> Or is there recent research saying that an HT thread is equivalent to a core
> for compute-intensive workloads?

This is a fun question. Processors that have hyperthreading duplicate the
parts of the CPU needed to maintain state, but they don't duplicate the parts
that run the actual logic. So if you compare a single core hyperthreaded
processor with a dual core processor without hyperthreading the dual core one
will be faster.

However it gets a bit more complicated than that. Oftentimes processors sit
idle while waiting for the rest of the system to catch up- for instance it may
have to wait for memory to get loaded from RAM. Processors with hyperthreading
see a boost in performance here because they can run the second thread while
waiting for the operations needed to run the first thread- thus making these
processors about 30% more efficient.

So while more cores are definitly better, if you are comparing two processors
with the same number of cores and all else is equal the ones with
hyperthreading will perform better.

One thing to note is that AWS provides vCPUs in pairs, so even though they are
giving you the number of threads you can always be sure you're getting
individual cores along with them.

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BenoitP
> These instances designed for compute-heavy applications like [...], highly
> scalable multiplayer gaming

Is he referring to specific titles? It's been a while, but to me, the max
lobby size for multiplayer games was stuck at ~70 concurrent players (sending
all updates to everyone is n^2).

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nivertech
I'm tired of updating my CloudFormation templates with the new instance types
every month.

Can AWS provide CFN template with all valid instance types, that I can import
in a CFN?

Maybe some other programmatic way as an API or CLI, i.e.:

    
    
        aws ec2 describe-instance-types

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pishpash
Price please.

~~~
btgeekboy
[https://aws.amazon.com/ec2/pricing/](https://aws.amazon.com/ec2/pricing/)

Be sure to pick a region where they're available, like us-east-1.

