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Subject[PATCH] percpu/module resevation: change resevation size iff X86_VSMP is set
Date
as reported in bug #201339 (https://bugzilla.kernel.org/show_bug.cgi?id=201339)
by enabling X86_VSMP, INTERNODE_CACHE_BYTES's definition differs from the default one
causing the struct size to exceed the size ok 8KB.

in order to avoid such issue, increse PERCPU_MODULE_RESERVE to 64KB if CONFIG_X86_VSMP is set.

the value was caculated on linux 4.20.3, make allmodconfig all and the following oneliner:
for f in `find -name *.ko`; do echo $f; readelf -S $f |grep perc; done |grep data..percpu -B 1 |grep ko |while read r; do echo -n "$r: "; objdump --syms --section=.data..percpu $r|grep data |sort -n |awk '{c++; d=strtonum("0x" $1) + strtonum("0x" $5); if (m < d) m = d;} END {printf("%d vars-> last addr 0x%x ( %d )\n", c, m, m)}' ; done |column -t |sort -k 8 -n | awk '{print $8}'| paste -sd+ | bc

Signed-off-by: Eial Czerwacki <eial@scalemp.com>
Signed-off-by: Shai Fultheim <shai@scalemp.com>
Signed-off-by: Oren Twaig <oren@scalemp.com>
---
include/linux/percpu.h | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 70b7123..6b79693 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -14,7 +14,11 @@

/* enough to cover all DEFINE_PER_CPUs in modules */
#ifdef CONFIG_MODULES
+#ifdef X86_VSMP
+#define PERCPU_MODULE_RESERVE (1 << 16)
+#else
#define PERCPU_MODULE_RESERVE (8 << 10)
+#endif
#else
#define PERCPU_MODULE_RESERVE 0
#endif
--
2.7.4
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