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Date: Mon, 5 May 2014 22:18:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Dan Streetman <ddstreet@...e.org>
Cc: Hugh Dickins <hughd@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>,
Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>,
Rik van Riel <riel@...hat.com>,
Weijie Yang <weijieut@...il.com>,
Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/4] plist: add plist_rotate
On Fri, 2 May 2014 15:02:29 -0400
Dan Streetman <ddstreet@...e.org> wrote:
> Add plist_rotate(), which moves the specified plist_node after
> all other same-priority plist_nodes in the list.
This is a little confusing? You mean it takes a plist_node from a plist
and simply moves it to the end of the list of all other nodes of the
same priority? Kind of like what a sched_yield() would do with a
SCHED_FIFO task? I wonder if we should call this "plist_yield()" then?
>
> This is needed by swap, which has a plist of swap_info_structs
> and needs to use each same-priority swap_info_struct equally.
"needs to use each same-priority swap_info_struct equally"
-ENOCOMPUTE
>
> Also add plist_test_rotate() test function, for use by plist_test()
> to test plist_rotate() function.
>
> Signed-off-by: Dan Streetman <ddstreet@...e.org>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
>
> ---
>
> This patch is new to this patch set, and it's required by the next patch,
> which needs a way to move a plist entry to the end of all following
> same-priority entries. This is possible to do manually instead of adding
> a new plist function, but having a common plist function instead of code
> specific only to swap seems preferable.
>
> include/linux/plist.h | 2 ++
> lib/plist.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 50 insertions(+)
>
> diff --git a/include/linux/plist.h b/include/linux/plist.h
> index c815491..06e6925 100644
> --- a/include/linux/plist.h
> +++ b/include/linux/plist.h
> @@ -141,6 +141,8 @@ static inline void plist_node_init(struct plist_node *node, int prio)
> extern void plist_add(struct plist_node *node, struct plist_head *head);
> extern void plist_del(struct plist_node *node, struct plist_head *head);
>
> +extern void plist_rotate(struct plist_node *node, struct plist_head *head);
> +
> /**
> * plist_for_each - iterate over the plist
> * @pos: the type * to use as a loop counter
> diff --git a/lib/plist.c b/lib/plist.c
> index 1ebc95f..a8b54e5 100644
> --- a/lib/plist.c
> +++ b/lib/plist.c
> @@ -134,6 +134,42 @@ void plist_del(struct plist_node *node, struct plist_head *head)
> plist_check_head(head);
> }
>
> +/**
> + * plist_rotate - Rotate @node to end of same-prio entries.
> + *
> + * @node: &struct plist_node pointer - entry to be moved
> + * @head: &struct plist_head pointer - list head
> + */
> +void plist_rotate(struct plist_node *node, struct plist_head *head)
> +{
> + struct plist_node *next;
> + struct list_head *next_node_list = &head->node_list;
Naming convention should be the same as plist_add() and call this
node_next instead of next_node_list.
-- Steve
> +
> + plist_check_head(head);
> + BUG_ON(plist_head_empty(head));
> + BUG_ON(plist_node_empty(node));
> +
> + if (node == plist_last(head))
> + return;
> +
> + next = plist_next(node);
> +
> + if (node->prio != next->prio)
> + return;
> +
> + plist_del(node, head);
> +
> + plist_for_each_continue(next, head) {
> + if (node->prio != next->prio) {
> + next_node_list = &next->node_list;
> + break;
> + }
> + }
> + list_add_tail(&node->node_list, next_node_list);
> +
> + plist_check_head(head);
> +}
> +
> #ifdef CONFIG_DEBUG_PI_LIST
> #include <linux/sched.h>
> #include <linux/module.h>
> @@ -170,6 +206,14 @@ static void __init plist_test_check(int nr_expect)
> BUG_ON(prio_pos->prio_list.next != &first->prio_list);
> }
>
> +static void __init plist_test_rotate(struct plist_node *node)
> +{
> + plist_rotate(node, &test_head);
> +
> + if (node != plist_last(&test_head))
> + BUG_ON(node->prio == plist_next(node)->prio);
> +}
> +
> static int __init plist_test(void)
> {
> int nr_expect = 0, i, loop;
> @@ -193,6 +237,10 @@ static int __init plist_test(void)
> nr_expect--;
> }
> plist_test_check(nr_expect);
> + if (!plist_node_empty(test_node + i)) {
> + plist_test_rotate(test_node + i);
> + plist_test_check(nr_expect);
> + }
> }
>
> for (i = 0; i < ARRAY_SIZE(test_node); i++) {
--
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