[CRIU] [PATCH 0/5] Speed up kdat checks (v2)

[Pavel Emelyanov]

On 04/27/2017 12:02 PM, Dmitry Safonov wrote:
> 2017-04-27 9:26 GMT+03:00 Andrei Vagin <avagin at virtuozzo.com>:
>> On Wed, Apr 26, 2017 at 02:05:52PM +0300, Dmitry Safonov wrote:
>>> 2017-04-26 13:26 GMT+03:00 Dmitry Safonov <0x7f454c46 at gmail.com>:
>>>> 2017-04-26 12:23 GMT+03:00 Pavel Emelyanov <xemul at virtuozzo.com>:
>>>>> In the previous discussion it was suggested not to compile-in
>>>>> the kdat bits, but rather cache them in some place, that gets
>>>>> evicted on node reboot.
>>>>>
>>>>> Here's how this can look like.
>>>>>
>>>>> Briefly -- when kerndat.c has finished auto-detection is writes
>>>>> the kdat variable into the /run/criu.kdat file. On the next
>>>>> start the file in question is loaded into memory (if present)
>>>>> as is.
>>>>>
>>>>> As the next step we can move the cpu_init() stuff into kdat and
>>>>> (as Dima suggested) vdso_init().
>>>>
>>>> Looks good to me,
>>>> Reviewed-by: Dmitry Safonov <dsafonov at virtuozzo.com>
>>>>
>>>> But I also suggest adding CRIU_GITID to that file (somewhere
>>>> at the beginning). So, if CRIU package has been updated and
>>>> kerndat_s was changed - to check the version and regenerate a file.
>>>
>>> Or maybe to simplify it for now and avoid synchronization,
>>> rely on package maintainer again and document somewhere that on
>>> CRIU's package update criu.kdat should be removed.
>>>
>>
>> maybe something like this?
> 
> Yep, that should work, LGTM.

OK, will incorporate this into v4, thanks :)

>> diff --git a/criu/Makefile.crtools b/criu/Makefile.crtools
>> index 03756ae..0815519 100644
>> --- a/criu/Makefile.crtools
>> +++ b/criu/Makefile.crtools
>> @@ -1,5 +1,6 @@
>>  ccflags-y              += -iquote criu/$(ARCH)
>>  ccflags-y              += $(COMPEL_UAPI_INCLUDES)
>> +CFLAGS_kerndat.o       += -DKDAT_MAGIC_2=${shell date +%s}
>>  CFLAGS_REMOVE_clone-noasan.o += $(CFLAGS-ASAN)
>>  ldflags-y              += -r
>>
>> diff --git a/criu/include/kerndat.h b/criu/include/kerndat.h
>> index 84d0707..1d3cf70 100644
>> --- a/criu/include/kerndat.h
>> +++ b/criu/include/kerndat.h
>> @@ -35,6 +35,7 @@ struct kerndat_s {
>>          * value to avoid loading of bad kdat bits.
>>          */
>>         u32 magic;
>> +       u32 magic2;
>>         dev_t shmem_dev;
>>         int last_cap;
>>         u64 zero_page_pfn;
>> diff --git a/criu/kerndat.c b/criu/kerndat.c
>> index d0f0d2b..a07f916 100644
>> --- a/criu/kerndat.c
>> +++ b/criu/kerndat.c
>> @@ -678,7 +678,8 @@ static int kerndat_try_load_cache(void)
>>
>>         close(fd);
>>
>> -       if (ret != sizeof(kdat) || kdat.magic != KDAT_MAGIC_1) {
>> +       if (ret != sizeof(kdat) ||
>> +           kdat.magic != KDAT_MAGIC_1 || kdat.magic2 != KDAT_MAGIC_2) {
>>                 pr_warn("Stale %s file\n", KERNDAT_CACHE_FILE);
>>                 unlink(KERNDAT_CACHE_FILE);
>>                 return 1;
>> @@ -719,6 +720,7 @@ static int kerndat_save_cache(void)
>>         }
>>
>>         kdat.magic = KDAT_MAGIC_1;
>> +       kdat.magic2 = KDAT_MAGIC_2;
>>         ret = write(fd, &kdat, sizeof(kdat));
>>         if (ret != sizeof(kdat))
>>                 pr_warn("Kerndat cache writing failed.\n");
>>
>>
>