[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZbfqVHA9+38/j3Mq@memverge.com>
Date: Mon, 29 Jan 2024 13:11:32 -0500
From: Gregory Price <gregory.price@...verge.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: Gregory Price <gourry.memverge@...il.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
corbet@....net, akpm@...ux-foundation.org, honggyu.kim@...com,
rakie.kim@...com, hyeongtak.ji@...com, mhocko@...nel.org,
vtavarespetr@...ron.com, jgroves@...ron.com,
ravis.opensrc@...ron.com, sthanneeru@...ron.com,
emirakhur@...ron.com, Hasan.Maruf@....com, seungjun.ha@...sung.com,
hannes@...xchg.org, dan.j.williams@...el.com
Subject: Re: [PATCH v3 4/4] mm/mempolicy: change cur_il_weight to atomic and
carry the node with it
On Mon, Jan 29, 2024 at 10:48:47AM -0500, Gregory Price wrote:
> On Mon, Jan 29, 2024 at 04:17:46PM +0800, Huang, Ying wrote:
> > Gregory Price <gregory.price@...verge.com> writes:
> >
> > But, in contrast, it's bad to put task-local "current weight" in
> > mempolicy. So, I think that it's better to move cur_il_weight to
> > task_struct. And maybe combine it with current->il_prev.
> >
> Style question: is it preferable add an anonymous union into task_struct:
>
> union {
> short il_prev;
> atomic_t wil_node_weight;
> };
>
> Or should I break out that union explicitly in mempolicy.h?
>
Having attempted this, it looks like including mempolicy.h into sched.h
is a non-starter. There are build issues likely associated from the
nested include of uapi/linux/mempolicy.h
So I went ahead and did the following. Style-wise If it's better to just
integrate this as an anonymous union in task_struct, let me know, but it
seemed better to add some documentation here.
I also added static get/set functions to mempolicy.c to touch these
values accordingly.
As suggested, I changed things to allow 0-weight in il_prev.node_weight
adjusted the logic accordingly. Will be testing this for a day or so
before sending out new patches.
~Gregory
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ffe8f618ab86..f0d2af3bbc69 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -745,6 +745,29 @@ struct kmap_ctrl {
#endif
};
+
+/*
+ * Describes task_struct interleave settings
+ *
+ * Interleave uses mpol_interleave.node
+ * last node allocated from
+ * intended for use in next_node_in() on the next allocation
+ *
+ * Weighted interleave uses mpol_interleave.node_weight
+ * node is the value of the current node to allocate from
+ * weight is the number of allocations left on that node
+ * when weight is 0, next_node_in(node) will be invoked
+ */
+union mpol_interleave {
+ struct {
+ short node;
+ short resv;
+ };
+ /* structure: short node; u8 resv; u8 weight; */
+ atomic_t node_weight;
+};
+
+
struct task_struct {
#ifdef CONFIG_THREAD_INFO_IN_TASK
/*
@@ -1258,7 +1281,7 @@ struct task_struct {
#ifdef CONFIG_NUMA
/* Protected by alloc_lock: */
struct mempolicy *mempolicy;
- short il_prev;
+ union mpol_interleave il_prev;
short pref_node_fork;
#endif
#ifdef CONFIG_NUMA_BALANCING
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 92740b8f0eb5..48e365b507b2 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -149,6 +149,66 @@ static struct mempolicy preferred_node_policy[MAX_NUMNODES];
static u8 __rcu *iw_table;
static DEFINE_MUTEX(iw_table_lock);
+static u8 get_il_weight(int node)
+{
+ u8 __rcu *table;
+ u8 weight;
+
+ rcu_read_lock();
+ table = rcu_dereference(iw_table);
+ /* if no iw_table, use system default */
+ weight = table ? table[node] : 1;
+ /* if value in iw_table is 0, use system default */
+ weight = weight ? weight : 1;
+ rcu_read_unlock();
+ return weight;
+}
+
+/* Clear any interleave values from task->il_prev */
+static void clear_il_prev(void)
+{
+ int node_weight;
+
+ node_weight = MAKE_WIL_PREV(MAX_NUMNODES - 1, 0);
+ atomic_set(¤t->il_prev.node_weight, node_weight);
+}
+
+/* get the next value for weighted interleave */
+static void get_wil_prev(int *node, u8 *weight)
+{
+ int node_weight;
+
+ node_weight = atomic_read(¤t->il_prev.node_weight);
+ *node = WIL_NODE(node_weight);
+ *weight = WIL_WEIGHT(node_weight);
+}
+
+/* set the next value for weighted interleave */
+static void set_wil_prev(int node, u8 weight)
+{
+ int node_weight;
+
+ if (node == MAX_NUMNODES)
+ node -= 1;
+ node_weight = MAKE_WIL_PREV(node, weight);
+ atomic_set(¤t->il_prev.node_weight, node_weight);
+}
+
+/* get the previous interleave node */
+static short get_il_prev(void)
+{
+ return current->il_prev.node;
+}
+
+/* set the previous interleave node */
+static void set_il_prev(int node)
+{
+ if (unlikely(node >= MAX_NUMNODES))
+ node = MAX_NUMNODES - 1;
+
+ current->il_prev.node = node;
+}
+
Powered by blists - more mailing lists