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

[Andrei Vagin]

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?

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
> _______________________________________________
> CRIU mailing list
> CRIU at openvz.org
> https://lists.openvz.org/mailman/listinfo/criu