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

[Dmitry Safonov]

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.

> 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");
>
>

-- 
             Dmitry