On 1/16/18 8:01 AM, Arnd Bergmann wrote: > Some older compilers (gcc-4.4 through 4.6 in particular) struggle > with the way that blkg_rwstat_read() returns a structure, leading > to excessive stack usage and rather inefficient code: > > block/blk-cgroup.c: In function 'blkg_destroy': > block/blk-cgroup.c:354:1: error: the frame size of 1296 bytes is larger than > 1024 bytes [-Werror=frame-larger-than=] > block/cfq-iosched.c: In function 'cfqg_stats_add_aux': > block/cfq-iosched.c:753:1: error: the frame size of 1928 bytes is larger than > 1024 bytes [-Werror=frame-larger-than=] > block/bfq-cgroup.c: In function 'bfqg_stats_add_aux': > block/bfq-cgroup.c:299:1: error: the frame size of 1928 bytes is larger than > 1024 bytes [-Werror=frame-larger-than=] > > I also notice that there is no point in using atomic accesses > for the local variables, so storing the temporaries in simple 'u64' > variables not only avoids the stack usage on older compilers but > also improves the object code on modern versions.
Added for 4.16, thanks Arnd. -- Jens Axboe
