> On Wed, Nov 29, 2023 at 12:51 AM Petr Vorel <pvorel@xxxxxxx> wrote: > > Hi Stefan, Li, > > > Hi Stefan, Petr, > > > On Tue, Nov 28, 2023 at 3:46 PM Petr Vorel <pvorel@xxxxxxx> wrote: > > > > Hi Stefan, > > > > > This disables the "smart scan" KSM feature to make sure that the > > volatile > > > > > count remains at 0. > > > > > Signed-off-by: Stefan Roesch <devkernel.io> > > > > nit: you forgot 'shr@' > > > > Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx> > > > > > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> > > > > > Closes: > > https://lore.kernel.org/oe-lkp/202311161132.13d8ce5a-oliver.sang@xxxxxxxxx > > > > > --- > > > > > testcases/kernel/mem/lib/mem.c | 4 ++++ > > > > > 1 file changed, 4 insertions(+) > > > > > diff --git a/testcases/kernel/mem/lib/mem.c > > > > b/testcases/kernel/mem/lib/mem.c > > > > > index fbfeef026..ef274a3ac 100644 > > > > > --- a/testcases/kernel/mem/lib/mem.c > > > > > +++ b/testcases/kernel/mem/lib/mem.c > > > > > @@ -454,6 +454,9 @@ void create_same_memory(int size, int num, int > > unit) > > > > > {'a', size*MB}, {'a', size*MB}, {'d', size*MB}, {'d', > > > > size*MB}, > > > > > }; > > > > > + /* Disable smart scan for correct volatile counts. */ > > > > > + SAFE_FILE_PRINTF(PATH_KSM "smart_scan", "0"); > > > > NOTE, this fails on the systems without /sys/kernel/mm/ksm/smart_scan: > > > > mem.c:458: TBROK: Failed to open FILE '/sys/kernel/mm/ksm/smart_scan' > > for > > > > writing: EACCES (13) > > > > NOTE, we normally handle the setup like this in test setup function. > > > > But new API has .save_restore which is more robust for tasks like > > this. > > > > It's already used in ksm01.c, you need just to add this line: > > > > {"/sys/kernel/mm/ksm/smart_scan", "0", TST_SR_SKIP}, > > > I guess we need to set 'TST_SR_SKIP_MISSING | TST_SR_TBROK_RO' > > > as the last field. Because TST_SR_SKIP will continue the test without > > > writing '0' to the smart_scan file, that's not correct if the file > > exists. > > > It will > > > ignore a kernel bug (smart_scan can't be written) by that config. > > > Per the Doc Petr pointed below: > > > TST_SR_SKIP_MISSING – Continue without saving the file if it does not > > > exist > > > TST_SR_TBROK_RO – End test with TBROK if the file is read-only > > > TST_SR_SKIP_RO – Continue without saving the file if it is read-only > > > TST_SR_SKIP – Equivalent to 'TST_SR_SKIP_MISSING | TST_SR_SKIP_RO' > > > > (instead of both SAFE_FILE_PRINTF) > > > > See: > > https://github.com/linux-test-project/ltp/wiki/C-Test-API#127-saving--restoring-procsys-values > > > > I wonder if ksm01.c is the only ksm test which needs to disable this. > > > I think all of the ksm0*.c tests should disable it by the config. The > > > smart_scan > > > will impact all the tests with invoke key function create_same_memory(). > > ksm05.c and ksm06.c does not use create_same_memory(). Or did I overlook > > something? > Good catch, I looked into these tests, seems only ksm05 is debatable > for disabling smart_scan, as a simple regression, it suggests disabling > ksm daemon to avoid disturb according to some workload. > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/ksm/ksm05.c#L30 > ksm06 is definitely need disable smart_scan, it tests KSM in different > 'run' state for merge_accros_nodes. Thanks for having a look. > To be on the safe side, I would suggest applying the patch to all ksm* > tests, > and write a new single for smart_scan if needed. Agree. I vote for new single for smart_scan related test. Kind regards, Petr
