On Wed, May 24, 2023 at 12:17:48PM +0200, David Sterba wrote: > Add a flag that allows to disable merging per slab. This can be used for > more fine grained control over the caches or for debugging builds where > separate slabs can verify that no objects leak. > The slab_nomerge boot option is too coarse and would need to be enabled > on all testing hosts. Hello David, There is no users nor interface to set this flag, I guess you're going to use it by modifying source code, when debugging? Does introducing new slub_debug option (i.e. slub_debug=N,pid_namespace) work for your use case? (there are some boot-time slub_debug options described in Documentation/mm/slub.rst) > There are some other ways how to disable merging, > e.g. a slab constructor but this disables poisoning besides that it adds > additional overhead. Other flags are internal and may have other > semantics. > > A concrete example what motivates the flag. During 'btrfs balance' slab > top reported huge increase in caches like > > 1330095 1330095 100% 0.10K 34105 39 136420K Acpi-ParseExt > 1734684 1734684 100% 0.14K 61953 28 247812K pid_namespace > 8244036 6873075 83% 0.11K 229001 36 916004K khugepaged_mm_slot > > which was confusing and that it's because of slab merging was not the > first idea. After rebooting with slab_nomerge all the caches were from > btrfs_ namespace as expected. > > Signed-off-by: David Sterba <dsterba@xxxxxxxx> > --- > include/linux/slab.h | 3 +++ > mm/slab_common.c | 2 +- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h Thanks, -- Hyeonggon Yoo Doing kernel stuff as a hobby Undergraduate | Chungnam National University Dept. Computer Science & Engineering
