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Message-ID: <20110906104728.GA21602@Krystal>
Date: Tue, 6 Sep 2011 06:47:28 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Huang Ying <ying.huang@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH -mm 1/4] llist, Make all llist functions inline
* Huang Ying (ying.huang@...el.com) wrote:
> Because llist may be used in performance critical code path, make all
> llist functions inline to avoid function calling overhead.
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Thanks,
Mathieu
>
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> ---
> drivers/acpi/apei/Kconfig | 1
> include/linux/llist.h | 122 +++++++++++++++++++++++++++++++++++++++++--
> lib/Kconfig | 3 -
> lib/Makefile | 2
> lib/llist.c | 129 ----------------------------------------------
> 5 files changed, 116 insertions(+), 141 deletions(-)
> delete mode 100644 lib/llist.c
>
> --- a/drivers/acpi/apei/Kconfig
> +++ b/drivers/acpi/apei/Kconfig
> @@ -14,7 +14,6 @@ config ACPI_APEI_GHES
> depends on ACPI_APEI && X86
> select ACPI_HED
> select IRQ_WORK
> - select LLIST
> select GENERIC_ALLOCATOR
> help
> Generic Hardware Error Source provides a way to report
> --- a/include/linux/llist.h
> +++ b/include/linux/llist.h
> @@ -37,8 +37,28 @@
> * architectures that don't have NMI-safe cmpxchg implementation, the
> * list can NOT be used in NMI handler. So code uses the list in NMI
> * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
> + *
> + * Copyright 2010,2011 Intel Corp.
> + * Author: Huang Ying <ying.huang@...el.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License version
> + * 2 as published by the Free Software Foundation;
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> */
>
> +#include <linux/kernel.h>
> +#include <asm/system.h>
> +#include <asm/processor.h>
> +
> struct llist_head {
> struct llist_node *first;
> };
> @@ -113,14 +133,104 @@ static inline void init_llist_head(struc
> * test whether the list is empty without deleting something from the
> * list.
> */
> -static inline int llist_empty(const struct llist_head *head)
> +static inline bool llist_empty(const struct llist_head *head)
> {
> return ACCESS_ONCE(head->first) == NULL;
> }
>
> -void llist_add(struct llist_node *new, struct llist_head *head);
> -void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
> - struct llist_head *head);
> -struct llist_node *llist_del_first(struct llist_head *head);
> -struct llist_node *llist_del_all(struct llist_head *head);
> +/**
> + * llist_add - add a new entry
> + * @new: new entry to be added
> + * @head: the head for your lock-less list
> + */
> +static inline void llist_add(struct llist_node *new, struct llist_head *head)
> +{
> + struct llist_node *entry, *old_entry;
> +
> +#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> + BUG_ON(in_nmi());
> +#endif
> +
> + entry = head->first;
> + do {
> + old_entry = entry;
> + new->next = entry;
> + cpu_relax();
> + } while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry);
> +}
> +
> +/**
> + * llist_add_batch - add several linked entries in batch
> + * @new_first: first entry in batch to be added
> + * @new_last: last entry in batch to be added
> + * @head: the head for your lock-less list
> + */
> +static inline void llist_add_batch(struct llist_node *new_first,
> + struct llist_node *new_last,
> + struct llist_head *head)
> +{
> + struct llist_node *entry, *old_entry;
> +
> +#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> + BUG_ON(in_nmi());
> +#endif
> +
> + entry = head->first;
> + do {
> + old_entry = entry;
> + new_last->next = entry;
> + cpu_relax();
> + } while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
> +}
> +
> +/**
> + * llist_del_first - delete the first entry of lock-less list
> + * @head: the head for your lock-less list
> + *
> + * If list is empty, return NULL, otherwise, return the first entry
> + * deleted, this is the newest added one.
> + *
> + * Only one llist_del_first user can be used simultaneously with
> + * multiple llist_add users without lock. Because otherwise
> + * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
> + * llist_add) sequence in another user may change @head->first->next,
> + * but keep @head->first. If multiple consumers are needed, please
> + * use llist_del_all or use lock between consumers.
> + */
> +static inline struct llist_node *llist_del_first(struct llist_head *head)
> +{
> + struct llist_node *entry, *old_entry, *next;
> +
> +#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> + BUG_ON(in_nmi());
> +#endif
> +
> + entry = head->first;
> + do {
> + if (entry == NULL)
> + return NULL;
> + old_entry = entry;
> + next = entry->next;
> + cpu_relax();
> + } while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
> +
> + return entry;
> +}
> +
> +/**
> + * llist_del_all - delete all entries from lock-less list
> + * @head: the head of lock-less list to delete all entries
> + *
> + * If list is empty, return NULL, otherwise, delete all entries and
> + * return the pointer to the first entry. The order of entries
> + * deleted is from the newest to the oldest added one.
> + */
> +static inline struct llist_node *llist_del_all(struct llist_head *head)
> +{
> +#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> + BUG_ON(in_nmi());
> +#endif
> +
> + return xchg(&head->first, NULL);
> +}
> #endif /* LLIST_H */
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -276,7 +276,4 @@ config CORDIC
> so its calculations are in fixed point. Modules can select this
> when they require this function. Module will be called cordic.
>
> -config LLIST
> - bool
> -
> endmenu
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -116,8 +116,6 @@ obj-$(CONFIG_CPU_RMAP) += cpu_rmap.o
>
> obj-$(CONFIG_CORDIC) += cordic.o
>
> -obj-$(CONFIG_LLIST) += llist.o
> -
> hostprogs-y := gen_crc32table
> clean-files := crc32table.h
>
> --- a/lib/llist.c
> +++ /dev/null
> @@ -1,129 +0,0 @@
> -/*
> - * Lock-less NULL terminated single linked list
> - *
> - * The basic atomic operation of this list is cmpxchg on long. On
> - * architectures that don't have NMI-safe cmpxchg implementation, the
> - * list can NOT be used in NMI handler. So code uses the list in NMI
> - * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
> - *
> - * Copyright 2010,2011 Intel Corp.
> - * Author: Huang Ying <ying.huang@...el.com>
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License version
> - * 2 as published by the Free Software Foundation;
> - *
> - * This program is distributed in the hope that it will be useful,
> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> - * GNU General Public License for more details.
> - *
> - * You should have received a copy of the GNU General Public License
> - * along with this program; if not, write to the Free Software
> - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> - */
> -#include <linux/kernel.h>
> -#include <linux/module.h>
> -#include <linux/interrupt.h>
> -#include <linux/llist.h>
> -
> -#include <asm/system.h>
> -
> -/**
> - * llist_add - add a new entry
> - * @new: new entry to be added
> - * @head: the head for your lock-less list
> - */
> -void llist_add(struct llist_node *new, struct llist_head *head)
> -{
> - struct llist_node *entry, *old_entry;
> -
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> - BUG_ON(in_nmi());
> -#endif
> -
> - entry = head->first;
> - do {
> - old_entry = entry;
> - new->next = entry;
> - cpu_relax();
> - } while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry);
> -}
> -EXPORT_SYMBOL_GPL(llist_add);
> -
> -/**
> - * llist_add_batch - add several linked entries in batch
> - * @new_first: first entry in batch to be added
> - * @new_last: last entry in batch to be added
> - * @head: the head for your lock-less list
> - */
> -void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
> - struct llist_head *head)
> -{
> - struct llist_node *entry, *old_entry;
> -
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> - BUG_ON(in_nmi());
> -#endif
> -
> - entry = head->first;
> - do {
> - old_entry = entry;
> - new_last->next = entry;
> - cpu_relax();
> - } while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
> -}
> -EXPORT_SYMBOL_GPL(llist_add_batch);
> -
> -/**
> - * llist_del_first - delete the first entry of lock-less list
> - * @head: the head for your lock-less list
> - *
> - * If list is empty, return NULL, otherwise, return the first entry
> - * deleted, this is the newest added one.
> - *
> - * Only one llist_del_first user can be used simultaneously with
> - * multiple llist_add users without lock. Because otherwise
> - * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
> - * llist_add) sequence in another user may change @head->first->next,
> - * but keep @head->first. If multiple consumers are needed, please
> - * use llist_del_all or use lock between consumers.
> - */
> -struct llist_node *llist_del_first(struct llist_head *head)
> -{
> - struct llist_node *entry, *old_entry, *next;
> -
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> - BUG_ON(in_nmi());
> -#endif
> -
> - entry = head->first;
> - do {
> - if (entry == NULL)
> - return NULL;
> - old_entry = entry;
> - next = entry->next;
> - cpu_relax();
> - } while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
> -
> - return entry;
> -}
> -EXPORT_SYMBOL_GPL(llist_del_first);
> -
> -/**
> - * llist_del_all - delete all entries from lock-less list
> - * @head: the head of lock-less list to delete all entries
> - *
> - * If list is empty, return NULL, otherwise, delete all entries and
> - * return the pointer to the first entry. The order of entries
> - * deleted is from the newest to the oldest added one.
> - */
> -struct llist_node *llist_del_all(struct llist_head *head)
> -{
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> - BUG_ON(in_nmi());
> -#endif
> -
> - return xchg(&head->first, NULL);
> -}
> -EXPORT_SYMBOL_GPL(llist_del_all);
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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