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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 1D3B6C433F4 for ; Thu, 30 Aug 2018 02:46:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ACD7020661 for ; Thu, 30 Aug 2018 02:46:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ACD7020661 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org 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 S1727247AbeH3GqG (ORCPT ); Thu, 30 Aug 2018 02:46:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:40166 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726457AbeH3GqG (ORCPT ); Thu, 30 Aug 2018 02:46:06 -0400 Received: from vmware.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 56DB620647; Thu, 30 Aug 2018 02:46:11 +0000 (UTC) Date: Wed, 29 Aug 2018 22:46:09 -0400 From: Steven Rostedt To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Tejun Heo Subject: Re: [PATCH tip/core/rcu 3/3] srcu: Make early-boot call_srcu() reuse workqueue lists Message-ID: <20180829224609.5ffdc9ec@vmware.local.home> In-Reply-To: <20180830020701.GE4225@linux.vnet.ibm.com> References: <20180829212036.GA22033@linux.vnet.ibm.com> <20180829212313.22903-3-paulmck@linux.vnet.ibm.com> <20180829215616.1c10e476@vmware.local.home> <20180830020701.GE4225@linux.vnet.ibm.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Aug 2018 19:07:01 -0700 "Paul E. McKenney" wrote: > On Wed, Aug 29, 2018 at 09:56:16PM -0400, Steven Rostedt wrote: > > On Wed, 29 Aug 2018 14:23:13 -0700 > > "Paul E. McKenney" wrote: > > > > > Allocating a list_head structure that is almost never used, and, when > > > used, is used only during early boot (rcu_init() and earlier), is a bit > > > wasteful. This commit therefore eliminates that list_head in favor of > > > the one in the work_struct structure. This is safe because the work_struct > > > structure cannot be used until after rcu_init() returns. > > > > > > Reported-by: Steven Rostedt > > > Signed-off-by: Paul E. McKenney > > > Cc: Tejun Heo > > > Cc: Lai Jiangshan > > > --- > > > include/linux/srcutiny.h | 2 -- > > > include/linux/srcutree.h | 3 +-- > > > kernel/rcu/srcutiny.c | 10 +++++----- > > > kernel/rcu/srcutree.c | 11 +++++------ > > > 4 files changed, 11 insertions(+), 15 deletions(-) > > > > > > diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h > > > index 2b5c0822e683..f41d2fb09f87 100644 > > > --- a/include/linux/srcutiny.h > > > +++ b/include/linux/srcutiny.h > > > @@ -36,7 +36,6 @@ struct srcu_struct { > > > struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ > > > struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ > > > struct work_struct srcu_work; /* For driving grace periods. */ > > > - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ > > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > > > struct lockdep_map dep_map; > > > #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > > @@ -49,7 +48,6 @@ void srcu_drive_gp(struct work_struct *wp); > > > .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ > > > .srcu_cb_tail = &name.srcu_cb_head, \ > > > .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ > > > - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ > > > __SRCU_DEP_MAP_INIT(name) \ > > > } > > > > > > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > > > index 9cfa4610113a..0ae91b3a7406 100644 > > > --- a/include/linux/srcutree.h > > > +++ b/include/linux/srcutree.h > > > @@ -94,7 +94,6 @@ struct srcu_struct { > > > /* callback for the barrier */ > > > /* operation. */ > > > struct delayed_work work; > > > - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ > > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > > > struct lockdep_map dep_map; > > > #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > > @@ -110,7 +109,7 @@ struct srcu_struct { > > > .sda = &pcpu_name, \ > > > .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ > > > .srcu_gp_seq_needed = -1UL, \ > > > - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ > > > + .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ > > > > Thanks! > > Glad you like it! Does it actually work for you? ;-) Oh, you want me to actually test it too? ;-) I'll try to add that in my todo list tomorrow. -- Steve > > Thanx, Paul > > > -- Steve > > > > > __SRCU_DEP_MAP_INIT(name) \ > > > } > > > > > > diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c > > > index d233f0c63f6f..b46e6683f8c9 100644 > > > --- a/kernel/rcu/srcutiny.c > > > +++ b/kernel/rcu/srcutiny.c > > > @@ -48,7 +48,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp) > > > sp->srcu_gp_waiting = false; > > > sp->srcu_idx = 0; > > > INIT_WORK(&sp->srcu_work, srcu_drive_gp); > > > - INIT_LIST_HEAD(&sp->srcu_boot_entry); > > > + INIT_LIST_HEAD(&sp->srcu_work.entry); > > > return 0; > > > } > > > > > > @@ -185,8 +185,8 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, > > > if (!READ_ONCE(sp->srcu_gp_running)) { > > > if (likely(srcu_init_done)) > > > schedule_work(&sp->srcu_work); > > > - else if (list_empty(&sp->srcu_boot_entry)) > > > - list_add(&sp->srcu_boot_entry, &srcu_boot_list); > > > + else if (list_empty(&sp->srcu_work.entry)) > > > + list_add(&sp->srcu_work.entry, &srcu_boot_list); > > > } > > > } > > > EXPORT_SYMBOL_GPL(call_srcu); > > > @@ -224,8 +224,8 @@ void __init srcu_init(void) > > > srcu_init_done = true; > > > while (!list_empty(&srcu_boot_list)) { > > > sp = list_first_entry(&srcu_boot_list, > > > - struct srcu_struct, srcu_boot_entry); > > > - list_del_init(&sp->srcu_boot_entry); > > > + struct srcu_struct, srcu_work.entry); > > > + list_del_init(&sp->srcu_work.entry); > > > schedule_work(&sp->srcu_work); > > > } > > > } > > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > > > index e79c1929328f..36a2857c84e0 100644 > > > --- a/kernel/rcu/srcutree.c > > > +++ b/kernel/rcu/srcutree.c > > > @@ -186,7 +186,6 @@ static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) > > > mutex_init(&sp->srcu_barrier_mutex); > > > atomic_set(&sp->srcu_barrier_cpu_cnt, 0); > > > INIT_DELAYED_WORK(&sp->work, process_srcu); > > > - INIT_LIST_HEAD(&sp->srcu_boot_entry); > > > if (!is_static) > > > sp->sda = alloc_percpu(struct srcu_data); > > > init_srcu_struct_nodes(sp, is_static); > > > @@ -709,8 +708,8 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, > > > if (likely(srcu_init_done)) > > > queue_delayed_work(rcu_gp_wq, &sp->work, > > > srcu_get_delay(sp)); > > > - else if (list_empty(&sp->srcu_boot_entry)) > > > - list_add(&sp->srcu_boot_entry, &srcu_boot_list); > > > + else if (list_empty(&sp->work.work.entry)) > > > + list_add(&sp->work.work.entry, &srcu_boot_list); > > > } > > > spin_unlock_irqrestore_rcu_node(sp, flags); > > > } > > > @@ -1324,10 +1323,10 @@ void __init srcu_init(void) > > > > > > srcu_init_done = true; > > > while (!list_empty(&srcu_boot_list)) { > > > - sp = list_first_entry(&srcu_boot_list, > > > - struct srcu_struct, srcu_boot_entry); > > > + sp = list_first_entry(&srcu_boot_list, struct srcu_struct, > > > + work.work.entry); > > > check_init_srcu_struct(sp); > > > - list_del_init(&sp->srcu_boot_entry); > > > + list_del_init(&sp->work.work.entry); > > > queue_work(rcu_gp_wq, &sp->work.work); > > > } > > > } > >