AW: AW: Block Cache

Tue Apr 29 11:55:11 CEST 2014

Hi,

The last time the build Problem was mit on Hardware, but on building it with the run/Demo for qemu.

This now works after the comments.

What haven't worked right now is using the live cd on real hardware. ( neither older L4 mir newer Linux live Demo)
So I asked to know wether a specific Plattform is known to work as I habe no Nova knowledge so far ( to reduce the risk of asking to many stupid questions).

Of I understand You correctly the was of using a filesystem with cache wozld be

ahci as driver -> blockcache as server -> rump_fs as single client of the blockcache and as server for -> multiple programs accessing files.

Is this correct?

Best regards
Wolfgang

----- Ursprüngliche Nachricht -----
Von: "Stefan Kalkowski" <stefan.kalkowski at ...1...>
Gesendet: ‎29.‎04.‎2014 09:37
An: "genode-main at lists.sourceforge.net" <genode-main at lists.sourceforge.net>
Betreff: Re: AW: Block Cache

Hi Wolfgang

On 04/28/2014 10:25 PM, Wolfgang Schmidt wrote:
> Hi Stefan,
> Can You give a gibt for compatible x86 hw? I tried The democd on an FSC
> Athlon64 which did mit start at all. Does for example a comp list for
> nova exist?

No, I've no compatibility list available. I know of quite different
Intel PCs people are using doing experiments with Genode/NOVA.

What do you mean with it didn't start at all on your specific hardware?
The last time I've read an email from you regarding problems with NOVA
on real hardware, it failed to compile the framebuffer driver, because
your third-party-code "libports" repository probably wasn't prepare
accordingly. Maybe it's better to smooth build problems out, instead of
searching for new hardware?

> 
> What so You mean with: it serves only one client- one client application?

I meant, the block cache acts like a block driver. In general a block
driver in Genode serves only one client, e.g.: a filesystem server. If
you want to share the same device with multiple clients, you might use
the "part_blk" server, which provides different partitions, found on the
device, as separate block sessions to different clients.

Does that clarifies your question?

Regards
Stefan

> 
> Best regards
> Wolfgang
> ------------------------------------------------------------------------
> Von: Stefan Kalkowski <mailto:stefan.kalkowski at ...1...>
> Gesendet: ‎28.‎04.‎2014 21:13
> An: genode-main at lists.sourceforge.net
> <mailto:genode-main at lists.sourceforge.net>
> Betreff: Re: Block Cache
> 
> Hi Wolfgang,
> 
> On 04/28/2014 08:27 PM, w_schmidt at ...181... wrote:
>> Hello,,
>>
>> I have a few question regarding genodes block cache in 14.02.
>>
>> If understand it correctly on x86-based computers genode starts on top of
>> linux.
> 
> well, that's not true. Yes, Genode is able to run on top of Linux,
> mostly for development purposes. But Genode runs also directly on x86
> hardware using the NOVA kernel, or Fiasco.OC kernel, or the OKL4 kernel,
> or Pistachio kernel.
> 
>> Therefore multiple caches will be used before something goes to genode
>> a) the cache on a hdd
>> b) cache on a drive controller
>> c) the linux block cache
> 
> If running on Linux yes, but normally it wouldn't make much sense to use
> an additional block cache here.
> 
>> d) qemu
> 
> As already said: you don't need to use Qemu. Most run scripts are
> starting Qemu by default, for convenience reasons only.
> 
>>
>> The first one is about the scenario in which the block cache is used.
>> Is the block cache only thought for embedded devices where genode runs
>> nativly? Are all embeded devices usable with the cache?
> 
> The block cache uses the block session of Genode. It uses exactly one
> block device, and serves exectly one client. As all block device drivers
> of Genode are implementing the block session interface, the block cache
> can be used on top of all block drivers, whether its a x86 AHCI driver,
> or MMC card driver of an ARM SoC, or whatever.
> 
>>
>> Is there a way to mount a partition in genode with qemu without using
> caches
>> from c) and d) ?
>> Or is there a x86 hardware where genode can directly operate on?
> 
> Qemu allows to define the caching policy of a hard drive (cache=none). I
> don't know whether it's possible to circumvent Linux block cache. I
> assume that's hard.
> But as mentioned above, you can use conventional x86 PC hardware.
> 
> Regards
> Stefan
> 
>>
>> As far as I have seen so far the disc cache of Linux does not seem to be
>> disablable. I have only foudn ways to flush linux cache (like sync &&
> echo 3
>>  > /proc/sys/vm/drop_caches).
>>
>> Best regards,
>> Wolfgang
>>
>>
>>
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> 
> -- 
> Stefan Kalkowski
> Genode Labs
> 
> http://www.genode-labs.com/ · http://genode.org/
> 
> ------------------------------------------------------------------------------
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-- 
Stefan Kalkowski
Genode Labs

http://www.genode-labs.com/ · http://genode.org/

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