* Re: [Qemu-devel] guest kernel in the host RAM
2015-12-15 11:27 ` [Qemu-devel] guest kernel in the host RAM Denis V. Lunev
@ 2015-12-15 11:59 ` Paolo Bonzini
2015-12-18 16:28 ` Denis V. Lunev
2015-12-16 3:18 ` Stefan Hajnoczi
2015-12-16 9:56 ` Miao Yan
2 siblings, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2015-12-15 11:59 UTC (permalink / raw)
To: Denis V. Lunev; +Cc: Vladimir Sementsov-Ogievskiy, QEMU
On 15/12/2015 12:27, Denis V. Lunev wrote:
> The idea is that we could boot with the uncompressed Linux
> kernel in the guest which serves 2 purposes:
> - faster boot time as per Intel opinion
> - memory savings
>
> Uncompressed kernel image could be the same for several
> guests and thus memory pages for the kernel could be the
> same, which saves a bit of RAM :)
>
> At the moment neither BIOS support this in full: nor SeaBIOS,
> nor OVMF, nor QBoot.
>
> From our point of view QBoot is an ideal candidate for this.
QBoot is not meant for use in production; SeaBIOS actually is just as
fast if you configure it right.
> Do you have any opinion for the topic?
I honestly don't like the idea. Linux patches itself a lot, which
makes the memory savings minimal (if they exist at all). What is the
decompression time for a kernel that is compressed with LZO?
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] guest kernel in the host RAM
2015-12-15 11:59 ` Paolo Bonzini
@ 2015-12-18 16:28 ` Denis V. Lunev
2015-12-18 18:03 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Denis V. Lunev @ 2015-12-18 16:28 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Vladimir Sementsov-Ogievskiy, QEMU
On 12/15/2015 02:59 PM, Paolo Bonzini wrote:
>
> On 15/12/2015 12:27, Denis V. Lunev wrote:
>> The idea is that we could boot with the uncompressed Linux
>> kernel in the guest which serves 2 purposes:
>> - faster boot time as per Intel opinion
>> - memory savings
>>
>> Uncompressed kernel image could be the same for several
>> guests and thus memory pages for the kernel could be the
>> same, which saves a bit of RAM :)
>>
>> At the moment neither BIOS support this in full: nor SeaBIOS,
>> nor OVMF, nor QBoot.
>>
>> From our point of view QBoot is an ideal candidate for this.
> QBoot is not meant for use in production; SeaBIOS actually is just as
> fast if you configure it right.
>
>> Do you have any opinion for the topic?
> I honestly don't like the idea. Linux patches itself a lot, which
> makes the memory savings minimal (if they exist at all). What is the
> decompression time for a kernel that is compressed with LZO?
>
> Paolo
It seems that you are perfectly correct here!
With large pages enabled (and preferred 2 Mb pages mode)
we will have exactly zero bonus.
Thank you for saving a lot of time and efforts :)))
Den
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] guest kernel in the host RAM
2015-12-18 16:28 ` Denis V. Lunev
@ 2015-12-18 18:03 ` Paolo Bonzini
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2015-12-18 18:03 UTC (permalink / raw)
To: Denis V. Lunev; +Cc: Vladimir Sementsov-Ogievskiy, qemu-devel
On 18/12/2015 17:28, Denis V. Lunev wrote:
>> Linux patches itself a lot, which
>> makes the memory savings minimal (if they exist at all). What is the
>> decompression time for a kernel that is compressed with LZO?
>
> It seems that you are perfectly correct here!
>
> With large pages enabled (and preferred 2 Mb pages mode)
> we will have exactly zero bonus.
>
> Thank you for saving a lot of time and efforts :)))
I'm a lazy person, sometimes it helps. :)
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] guest kernel in the host RAM
2015-12-15 11:27 ` [Qemu-devel] guest kernel in the host RAM Denis V. Lunev
2015-12-15 11:59 ` Paolo Bonzini
@ 2015-12-16 3:18 ` Stefan Hajnoczi
2015-12-16 9:56 ` Miao Yan
2 siblings, 0 replies; 6+ messages in thread
From: Stefan Hajnoczi @ 2015-12-16 3:18 UTC (permalink / raw)
To: Denis V. Lunev; +Cc: Paolo Bonzini, markmb, Vladimir Sementsov-Ogievskiy, QEMU
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On Tue, Dec 15, 2015 at 02:27:14PM +0300, Denis V. Lunev wrote:
> There is a plan or idea to improve current implementation
> of Clear Containers for QEMU. Patches about NVDIMM
> are floating in the list, you have proposed special
> boot firmware for a case.
By the way, Marc Mari is working on adding fw_cfg DMA support to
linuxboot.bin in QEMU. That way kernel/initramfs loading is much
quicker because it doesn't use PIO to read data from the host.
Stefan
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] guest kernel in the host RAM
2015-12-15 11:27 ` [Qemu-devel] guest kernel in the host RAM Denis V. Lunev
2015-12-15 11:59 ` Paolo Bonzini
2015-12-16 3:18 ` Stefan Hajnoczi
@ 2015-12-16 9:56 ` Miao Yan
2 siblings, 0 replies; 6+ messages in thread
From: Miao Yan @ 2015-12-16 9:56 UTC (permalink / raw)
To: Denis V. Lunev; +Cc: Paolo Bonzini, Vladimir Sementsov-Ogievskiy, QEMU
2015-12-15 19:27 GMT+08:00 Denis V. Lunev <den@openvz.org>:
> Hello, Paolo!
>
> There is a plan or idea to improve current implementation
> of Clear Containers for QEMU. Patches about NVDIMM
> are floating in the list, you have proposed special
> boot firmware for a case.
>
> The idea is that we could boot with the uncompressed Linux
> kernel in the guest which serves 2 purposes:
> - faster boot time as per Intel opinion
> - memory savings
>
> Uncompressed kernel image could be the same for several
> guests and thus memory pages for the kernel could be the
> same, which saves a bit of RAM :)
>
> At the moment neither BIOS support this in full: nor SeaBIOS,
> nor OVMF, nor QBoot.
Just FYI, U-boot can load uncompressed kernels and it can
run on qemu.
>
> From our point of view QBoot is an ideal candidate for this.
>
> Do you have any opinion for the topic?
>
> Den
>
^ permalink raw reply [flat|nested] 6+ messages in thread