From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01F99C04ABB for ; Tue, 11 Sep 2018 18:42:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0D1920865 for ; Tue, 11 Sep 2018 18:42:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tZuNmPTw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B0D1920865 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728451AbeIKXmx (ORCPT ); Tue, 11 Sep 2018 19:42:53 -0400 Received: from mail-yb1-f193.google.com ([209.85.219.193]:45591 "EHLO mail-yb1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726622AbeIKXmb (ORCPT ); Tue, 11 Sep 2018 19:42:31 -0400 Received: by mail-yb1-f193.google.com with SMTP id h22-v6so9713332ybg.12; Tue, 11 Sep 2018 11:41:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=r2kxmE2i/F4zOX3cOoXMsnwx5/PIHFb0myqGCKQDXp8=; b=tZuNmPTwD++oiilT/SKFfVULg1rxGXW6srQaCTr04qW0cVciRTV5lzHvQurnUDbR9S llwwaZ1SwqS6vKH/uRmSlH+ITvlRmRVjgvIK57VjYCvS8b5HS4M/6ez7ixHpkvVuoQ5y CJjmws4EfPwseBRRXBGqXFU3FnbcBww8pTN+3YvfM2aeItvfjYt2aq6QyLGrL5IuoKa7 666KDlW9aPbob9Pg6IqOb++VDEbZAcpdbLU4j/bHtqmN67tU9kfKhaicyqjPmD5Dzmq3 w86C42pzxSPdb3S26HRTyORjWXRc46Wd87zC33NFnnJ7zNoRl0yJrvedYk9PloZQ0/0g ygxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=r2kxmE2i/F4zOX3cOoXMsnwx5/PIHFb0myqGCKQDXp8=; b=gtHQiS5ndzO1CoQom9M4PQ5wvzQMDRwn5VFK7EgKZvHcK5R6CMZuFrLDG0UjLWk6nO 3FX5QtAOqRyZ+YBF0iGaxgo3rOJUFP+OshlAnSNZH+KDrG81ULAZY14oAl46j679BYEO 5Qj3jJoqx/o89z1amF6BnM+VE+EGDDTk308GyIyJMPjpcnscGPLM61oMKEqZ9Cw4Hf44 GMvCnPH3srdUmtihA5dpjNsUY7Drneyz3cZtqh2fOmruRC3oLoEi9YVNCrd290YXFpAJ 2hXSfoagZBweOTs3jAZqkCzfd+7p4MLABNpcYKVLHz1tSWmOy/m1yGtaV6/m/BFz3AfJ jfZA== X-Gm-Message-State: APzg51DLLtlmOrYFXyaAVxo6d3jykN0uXXWJ66QtqKMRmvkmHZq0OmYE mpazT0mfZtHUaD/db51iYAM= X-Google-Smtp-Source: ANB0VdaHkU2p3IGJxzGy2ULStRpRbMdsR8aZ+E6JzrwiU55GQp3d4BSD6ysNPvAJlnHL5DNbUSQtHg== X-Received: by 2002:a25:ea51:: with SMTP id o17-v6mr1341956ybe.172.1536691314982; Tue, 11 Sep 2018 11:41:54 -0700 (PDT) Received: from dennisz-mbp.thefacebook.com ([199.201.65.129]) by smtp.gmail.com with ESMTPSA id i123-v6sm7902875ywe.14.2018.09.11.11.41.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Sep 2018 11:41:53 -0700 (PDT) From: Dennis Zhou To: Jens Axboe , Tejun Heo , Johannes Weiner , Josef Bacik Cc: kernel-team@fb.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, "Dennis Zhou (Facebook)" Subject: [PATCH 10/12] blkcg: cleanup and make blk_get_rl use blkg_lookup_create Date: Tue, 11 Sep 2018 14:41:35 -0400 Message-Id: <20180911184137.35897-11-dennisszhou@gmail.com> X-Mailer: git-send-email 2.13.5 In-Reply-To: <20180911184137.35897-1-dennisszhou@gmail.com> References: <20180911184137.35897-1-dennisszhou@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Dennis Zhou (Facebook)" blk_get_rl is responsible for identifying which request_list a request should be allocated to. Try get logic was added earlier, but semantically the logic was not changed. This patch makes better use of the bio already having a reference to the blkg in the hot path. The cold path uses a better fallback of blkg_lookup_create rather than just blkg_lookup and then falling back to the q->root_rl. If lookup_create fails with anything but -ENODEV, it falls back to q->root_rl. A clarifying comment is added to explain why q->root_rl is used rather than the root blkg's rl. Signed-off-by: Dennis Zhou Acked-by: Tejun Heo --- include/linux/blk-cgroup.h | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index 2951ea3541b1..d2f7f1b00fcf 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -586,28 +586,36 @@ static inline struct request_list *blk_get_rl(struct request_queue *q, rcu_read_lock(); - blkcg = bio_blkcg(bio); - if (!blkcg) - blkcg = css_to_blkcg(blkcg_css()); + if (bio && bio->bi_blkg) { + blkcg = bio->bi_blkg->blkcg; + if (blkcg == &blkcg_root) + goto rl_use_root; + + blkg_get(bio->bi_blkg); + rcu_read_unlock(); + return &bio->bi_blkg->rl; + } - /* bypass blkg lookup and use @q->root_rl directly for root */ + blkcg = css_to_blkcg(blkcg_css()); if (blkcg == &blkcg_root) - goto root_rl; + goto rl_use_root; - /* - * Try to use blkg->rl. blkg lookup may fail under memory pressure - * or if either the blkcg or queue is going away. Fall back to - * root_rl in such cases. - */ blkg = blkg_lookup(blkcg, q); if (unlikely(!blkg)) - goto root_rl; + blkg = __blkg_lookup_create(blkcg, q); if (!blkg_try_get(blkg)) - goto root_rl; + goto rl_use_root; + rcu_read_unlock(); return &blkg->rl; -root_rl: + + /* + * Each blkg has its own request_list, however, the root blkcg + * uses the request_queue's root_rl. This is to avoid most + * overhead for the root blkcg. + */ +rl_use_root: rcu_read_unlock(); return &q->root_rl; } -- 2.17.1