[CRIU] [PATCH 0/12] Speed up kdat checks

[Pavel Emelyanov]

On 04/25/2017 02:28 PM, Dmitry Safonov wrote:
> 2017-04-24 23:06 GMT+03:00 Pavel Emelyanov <xemul at virtuozzo.com>:
>> Hi
>>
>> I've been experimenting with criu restore times recently and the first
>> thing I've met was -- criu does a lot of slow checks on start in kerndat.c.
>>
>> Here's the proposal (not extremely elegant, though) how to fix this.
>>
>> We have a .config which is created empty on default built, but anyone can
>> put data into it and they will result in CONFIG_BLAH_BLAH propagates into
>> criu sources.
>>
>> The proposal is to introduce a set of config options for those kerndat.c
>> checks, that are "immutable" for a given node. Examples are in patches :)
>>
>> Also I've created the scripts/mklocalconfig.sh script that creates a
>> .config for local node. To determine some of the options the script runs
>> 'criu check --feature foo' command, which is ... not very nice, as one
>> need to build criu twice -- once to get "default" criu, then to get
>> configured criu.
>>
>> Suggestions on improving this are very welcome.
> 
> So, it'll need recompiling criu according to each node?

Yes :( And that's the thing I don't like myself.

> Just as a suggestion: have you considered making them
> not compile-time, but runtime in /etc/criu.conf or something?

I did, but my plan was to save as much syscalls as possible and
opening reading and closing /etc/criu.conf is more VFS accesses than
I wanted.

> One read and parsing config will not hurt much, as we'll
> need to do it anyway for other options.
> I don't mind, just node's config file looks like more convenient
> way to me.

True, but from my perspective I'd better have non-criu binary that
would generate local config (if necessary) by using the same code as
criu does for auto-detection.

-- Pavel