On Fri, 22 Apr 2022, Peter Collingbourne wrote: > When CONFIG_KASAN_HW_TAGS is enabled we currently increase the minimum > slab alignment to 16. This happens even if MTE is not supported in > hardware or disabled via kasan=off, which creates an unnecessary > memory overhead in those cases. Eliminate this overhead by making > the minimum slab alignment a runtime property and only aligning to > 16 if KASAN is enabled at runtime. > > On a DragonBoard 845c (non-MTE hardware) with a kernel built with > CONFIG_KASAN_HW_TAGS, waiting for quiescence after a full Android > boot I see the following Slab measurements in /proc/meminfo (median > of 3 reboots): > > Before: 169020 kB > After: 167304 kB > > Link: https://linux-review.googlesource.com/id/I752e725179b43b144153f4b6f584ceb646473ead > Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> > Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> The command line options are described by Documentation/dev-tools/kasan.rst but it doesn't look like a update is necessary. I think the assumption today is that if we're using kasan=off then we aren't doing the alignment. I do wonder why kasan=off is not at least mentioned in Documentation/admin-guide/kernel-parameters.txt and perhaps for all other kasan options point the reader to Documentation/dev-tools/kasan.rst.
