From a524d9b48b9412e2c5fe83f1b29f81e365a39874 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sun, 16 Jun 2024 12:02:19 -0300
Subject: [PATCH] pmm: list tails and better standby page handling

---
 kernel-src/mm/pmm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel-src/mm/pmm.c b/kernel-src/mm/pmm.c
index 5570b442..46c0ade7 100644
--- a/kernel-src/mm/pmm.c
+++ b/kernel-src/mm/pmm.c
@@ -14,7 +14,9 @@ size_t freepagecount;
 
 static mutex_t freelistmutex;
 static page_t *freelists[PMM_SECTION_COUNT];
+static page_t *freetails[PMM_SECTION_COUNT];
 static page_t *standbylists[PMM_SECTION_COUNT];
+static page_t *standbytails[PMM_SECTION_COUNT];
 
 typedef struct {
 	uintmax_t baseid;
@@ -51,6 +53,7 @@ static void insertinfreelist(page_t *page) {
 	uintmax_t pageid = PAGE_GETID(page);
 	PAGE_BOUNDARYCHECK(pageid);
 	struct page_t **list;
+	struct page_t **tail;
 
 	int section;
 
@@ -62,6 +65,7 @@ static void insertinfreelist(page_t *page) {
 		section = PMM_SECTION_DEFAULT;
 
 	list = page->backing ? &standbylists[section] : &freelists[section];
+	tail = page->backing ? &standbytails[section] : &freetails[section];
 
 	if (sections[section].searchstart > pageid)
 		sections[section].searchstart = pageid;
@@ -71,6 +75,8 @@ static void insertinfreelist(page_t *page) {
 	*list = page;
 	if (page->freenext)
 		page->freenext->freeprev = page;
+	else
+		*tail = page;
 
 	++freepagecount;
 }
@@ -79,6 +85,7 @@ static void removefromfreelist(page_t *page) {
 	uintmax_t pageid = PAGE_GETID(page);
 	PAGE_BOUNDARYCHECK(pageid);
 	struct page_t **list;
+	struct page_t **tail;
 
 	int section;
 
@@ -90,6 +97,7 @@ static void removefromfreelist(page_t *page) {
 		section = PMM_SECTION_DEFAULT;
 
 	list = page->backing ? &standbylists[section] : &freelists[section];
+	tail = page->backing ? &standbytails[section] : &freetails[section];
 
 	if (page->freeprev)
 		page->freeprev->freenext = page->freenext;
@@ -98,6 +106,8 @@ static void removefromfreelist(page_t *page) {
 
 	if (page->freenext)
 		page->freenext->freeprev = page->freeprev;
+	else
+		*tail = page->freeprev;
 
 	--freepagecount;
 }
@@ -165,10 +175,9 @@ void *pmm_allocpage(int section) {
 	bool cachepage = false;
 
 	// if that wasn't possible, try to take from the cache standby list
-	// TODO do this FIFO rather than LIFO
 	if (page == NULL) {
 		for (int i = section; i >= 0; --i) {
-			page = standbylists[i];
+			page = standbytails[i];
 			if (page) {
 				cachepage = true;
 				internalhold(page);