On Wed, 04 Sep 2024, Andrew Morton wrote:\n
On Wed, 4 Sep 2024 09:27:40 -0700 Davidlohr Bueso <dave@xxxxxxxxxxxx> wrote:
This adds support for allowing proactive reclaim in general on a
NUMA system. A per-node interface extends support for beyond a
memcg-specific interface, respecting the current semantics of
memory.reclaim: respecting aging LRU and not supporting
artificially triggering eviction on nodes belonging to non-bottom
tiers.
This patch allows userspace to do:
echo 512M swappiness=10 > /sys/devices/system/node/nodeX/reclaim
One value per sysfs file is a rule.
I wasn't aware of it as a rule - is this documented somewhere?
I ask because I see some others are using space-separated parameters, ie:
/sys/bus/usb/drivers/foo/new_id
... or colons. What would be acceptable? echo "512M:10" > ... ?
+What: /sys/devices/system/node/nodeX/reclaim
+Date: September 2024
+Contact: Linux Memory Management list <linux-mm@xxxxxxxxx>
+Description:
+ This is write-only nested-keyed file which accepts the number of
"is a write-only".
What does "nested keyed" mean?
Will re-phrase.
+ bytes to reclaim as well as the swappiness for this particular
+ operation. Write the amount of bytes to induce memory reclaim in
+ this node. When it completes successfully, the specified amount
+ or more memory will have been reclaimed, and -EAGAIN if less
+ bytes are reclaimed than the specified amount.
Could be that this feature would benefit from a more expansive
treatment under Documentation/somewhere.
Sure.
...
+#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+
+enum {
+ MEMORY_RECLAIM_SWAPPINESS = 0,
+ MEMORY_RECLAIM_NULL,
+};
+
+static const match_table_t tokens = {
+ { MEMORY_RECLAIM_SWAPPINESS, "swappiness=%d"},
+ { MEMORY_RECLAIM_NULL, NULL },
+};
+
+static ssize_t reclaim_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int nid = dev->id;
+ gfp_t gfp_mask = GFP_KERNEL;
+ struct pglist_data *pgdat = NODE_DATA(nid);
+ unsigned long nr_to_reclaim, nr_reclaimed = 0;
+ unsigned int nr_retries = MAX_RECLAIM_RETRIES;
+ int swappiness = -1;
+ char *old_buf, *start;
+ substring_t args[MAX_OPT_ARGS];
+ struct scan_control sc = {
+ .gfp_mask = current_gfp_context(gfp_mask),
+ .reclaim_idx = gfp_zone(gfp_mask),
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = 1,
+ .proactive = 1,
+ };
+
+ buf = strstrip((char *)buf);
+
+ old_buf = (char *)buf;
+ nr_to_reclaim = memparse(buf, (char **)&buf) / PAGE_SIZE;
+ if (buf == old_buf)
+ return -EINVAL;
+
+ buf = strstrip((char *)buf);
+
+ while ((start = strsep((char **)&buf, " ")) != NULL) {
+ if (!strlen(start))
+ continue;
+ switch (match_token(start, tokens, args)) {
+ case MEMORY_RECLAIM_SWAPPINESS:
+ if (match_int(&args[0], &swappiness))
+ return -EINVAL;
+ if (swappiness < MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS)
+ return -EINVAL;
Code forgot to use local `swappiness' for any purpose?
Bleh, yeah sc.proactive_swappiness needs to be set here.
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+
...
