From: Eric Dumazet I noticed this vmlinux layout on i686 (where CONFIG_X86_L1_CACHE_SHIFT = 7) : c06cdab4 d pid_caches_lh c06cdb00 d qlowmark c06cdb04 d qhimark c06cdb08 d blimit c06cdb80 d rcu_ctrlblk c06cdc80 d rcu_bh_ctrlblk This means that qlowmark, qhimark and blimit use a whole 128 bytes cache line. Linker is not smart enough for us. Moving these three variables to read_mostly section saves 116 (128-12) bytes. # size vmlinux vmlinux.before_patch text data bss dec hex filename 6343966 490818 630784 7465568 71ea60 vmlinux 6343966 490930 630784 7465680 71ead0 vmlinux.before_patch Signed-off-by: Eric Dumazet Cc: "Paul E. McKenney" Cc: Dipankar Sarma Signed-off-by: Andrew Morton --- kernel/rcupdate.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff -puN kernel/rcupdate.c~rcu-move-three-variables-to-__read_mostly-to-save-space kernel/rcupdate.c --- a/kernel/rcupdate.c~rcu-move-three-variables-to-__read_mostly-to-save-space +++ a/kernel/rcupdate.c @@ -75,9 +75,9 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_d /* Fake initialization required by compiler */ static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL}; -static int blimit = 10; -static int qhimark = 10000; -static int qlowmark = 100; +static int blimit __read_mostly = 10; +static int qhimark __read_mostly = 10000; +static int qlowmark __read_mostly = 100; static atomic_t rcu_barrier_cpu_count; static DEFINE_MUTEX(rcu_barrier_mutex); _