Messages in this thread | | | Date | Mon, 18 Sep 2017 20:26:55 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH] blkcg: simplify statistic accumulation code |
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On Fri, Sep 15, 2017 at 09:36:21PM +0200, 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. > > Fixes: e6269c445467 ("blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead_stats with it") > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Tejun Heo <tj@kernel.org>
Thanks.
-- tejun
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