From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751894AbdIOThH (ORCPT ); Fri, 15 Sep 2017 15:37:07 -0400 Received: from mout.kundenserver.de ([217.72.192.74]:53212 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633AbdIOThG (ORCPT ); Fri, 15 Sep 2017 15:37:06 -0400 From: Arnd Bergmann To: Tejun Heo Cc: Arnd Bergmann , Jens Axboe , Tahsin Erdogan , Bart Van Assche , Shaohua Li , Nikolay Borisov , linux-kernel@vger.kernel.org Subject: [PATCH] blkcg: simplify statistic accumulation code Date: Fri, 15 Sep 2017 21:36:21 +0200 Message-Id: <20170915193647.1102621-1-arnd@arndb.de> X-Mailer: git-send-email 2.9.0 X-Provags-ID: V03:K0:K0ed7hlMHdAcxmmMPbV6Io1FJJSQDN0r+Hmx7v1ZjEgaQ2L5D6Q DbJaMtGAP/BGMu04T7GmKE17RCuwYp7YWJ/Nj5IgHI9Zar3hoEz7KyT6nNxfvu6kJAywscc +HqpQUPNumOuN6SYLkM90aCBZX0fxzt6fIAoeLlbw9gpBFh7eIKDbvrRMNpNjpiHLwF4ZVG dVCqoI/FZdYp2W3dle+kA== X-UI-Out-Filterresults: notjunk:1;V01:K0:vR/xvZ8M7is=:cKV9Ao/POzKrOQ1n9LTo19 LzVhnegsrjz5Hh7Zlzgcn3BIIGwXSJ0IMcRwZrUuEWHr2B0WGHbyhGWelxijKe0jeliVmugWo kaO5TUhhnjYRqH6h4A5uwVvnNKnxJvpR2uc3uc4vAqzUhaSLoHu8tBYdbeGPTtNHlYKKeFqB1 mD73KUZ5keP0IXd9g9YNUmJSdLnbDaIl83beFhbk+UDklazPssfdMF72CWq2DGRNdRUHCh6q+ P5XwVAe0MKHArg/0PQVtyILbNfzntkplHMlN69xXeiWlY8lOkP1Im1QHi4zwOJz6T0KziqIlH suiWKYKtAsNQCvd0WmtprjyMFs3tMxt4nFqT2TYoUFPSXt6U1JlFXGfFYvbC5ycyLOB03bfAu upq7zYYOvUE1TtqhR5FUdIB0rXpE42YTIn3VFyXOySdzaWLl7shypjgHmVZh1C/4Inw1fn7r2 ClCqd4693DdNvyo8VVd2JsaUybf1T8M4od5dwtk5A0CMQ+IIVNT7rj6PHRInsIDwrwtGTSnMH MonERSYMJdpMq9wn3Ca2YnTSuQsV/dQnxaPYA/rWNjnjIir1xyNTfuRsY5ciXQOIdEIVEm+Zu C0whyEKnilPuBGlwzjYkYe3J1hchgI01WjXf0txQL9IizUHF/tPY5sKhKClXGnSk2HfCnzWcw yztPaKVj05IZDANWZ1ZziXyGbLzvHn/rQLi7Re1/G/jtJqb+yLvk3myyQCCy4wuM2hqmnS0VH Cl/ZwN5DZ9MJ2w2KzD5SHTfXffbgnjG/kCTBsQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- include/linux/blk-cgroup.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index 9d92153dd856..2f1ff739ea52 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -664,12 +664,14 @@ static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat) static inline void blkg_rwstat_add_aux(struct blkg_rwstat *to, struct blkg_rwstat *from) { - struct blkg_rwstat v = blkg_rwstat_read(from); + u64 sum[BLKG_RWSTAT_NR]; int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) - atomic64_add(atomic64_read(&v.aux_cnt[i]) + - atomic64_read(&from->aux_cnt[i]), + sum[i] = percpu_counter_sum_positive(&from->cpu_cnt[i]); + + for (i = 0; i < BLKG_RWSTAT_NR; i++) + atomic64_add(sum[i] + atomic64_read(&from->aux_cnt[i]), &to->aux_cnt[i]); } -- 2.9.0