From 76517486919657ecadda9867125dc6730f29a5b7 Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Sat, 6 Jul 2024 18:14:04 +0300
Subject: pretty massive virtual memory rewrite

+ The system is now a bit simpler and hopefully easier to understand, while also
  extending the shared memory to be 1:N, where there is one owner who
  may become a zombie while waiting for the N to die.
---
 src/mem_regions.c | 582 ------------------------------------------------------
 1 file changed, 582 deletions(-)
 delete mode 100644 src/mem_regions.c

(limited to 'src/mem_regions.c')

diff --git a/src/mem_regions.c b/src/mem_regions.c
deleted file mode 100644
index 707c2f0..0000000
--- a/src/mem_regions.c
+++ /dev/null
@@ -1,582 +0,0 @@
-/* SPDX-License-Identifier: copyleft-next-0.3.1 */
-/* Copyright 2021 - 2022, Kim Kuparinen < kimi.h.kuparinen@gmail.com > */
-
-/**
- * @file mem_regions.c
- * Memory region handling, used by both device memory and user virtual memory
- * subsystems.
- */
-
-#include <kmi/mem_regions.h>
-#include <kmi/mem_nodes.h>
-#include <kmi/pmem.h>
-#include <kmi/bits.h>
-#include <kmi/mem.h>
-
-/**
- * Readability wrapper for marking region used.
- *
- * @param r Region flags to set.
- */
-#define mark_region_used(r) set_bit(r, MR_USED)
-
-/**
- * Readability wrapper for marking region unused.
- *
- * @param r Region flags to clear.
- */
-#define mark_region_unused(r) clear_bit(r, MR_USED)
-
-/* pretty major slowdown when we get to some really massive numbers, not
- * entirely sure why. Will need to check up on this at some point, have I
- * somehow managed to come up with a _very_ bad situation for my sp_trees?
- *
- * EDIT: apparently, yeah. Max depth of 106 with a million entries, interesting.
- * I guess since in this scenario all sizes are 1, and I just shove everything
- * to the right? Maybe?
- *
- * EDIT upon EDIT: yeah, when taking the start position of the region into
- * account we get a much more sensible max depth of 39 for 5 million entries.
- * Seems I have found a weakness in sp_trees :D
- *
- * Duplicate entries don't work well with any trees, I think. Good to know,
- * maybe not even anything with sp_trees but more a weakness of binary trees in
- * general?
- */
-
-/**
- * Insert free memory region.
- *
- * @param r Memory region root to insert \c m into.
- * @param m Free memory region to insert.
- * @return \c m.
- */
-static struct mem_region *__insert_free_region(struct mem_region_root *r,
-                                               struct mem_region *m)
-{
-	/* this could be simplified by using my gsptrees in kmx, but at least
-	 * this ensures 'inlining' of the condition checking so I'll let it stay
-	 * for now */
-	struct sp_node *n = sp_root(&r->free_regions), *p = NULL;
-	vm_t start = m->start;
-	size_t size = m->end - m->start;
-	enum sp_dir d = SP_LEFT;
-
-	m->sp_n = (struct sp_node){ 0 };
-
-	while (n) {
-		struct mem_region *t = mem_container(n);
-		size_t nsize = t->end - t->start;
-		p = n;
-
-		if (size < nsize) {
-			n = sp_left(n);
-			d = SP_LEFT;
-		}
-
-		else if (size > nsize) {
-			n = sp_right(n);
-			d = SP_RIGHT;
-		}
-
-		else if (start < t->start) {
-			n = sp_left(n);
-			d = SP_LEFT;
-		}
-
-		else {
-			n = sp_right(n);
-			d = SP_RIGHT;
-		}
-	}
-
-	sp_insert(&sp_root(&r->free_regions), p, &m->sp_n, d);
-	return m;
-}
-
-/**
- * Insert used memory region.
- *
- * @param r Memory region root to insert \c m into.
- * @param m Memory region to insert.
- * @return \c m.
- */
-static struct mem_region *__insert_used_region(struct mem_region_root *r,
-                                               struct mem_region *m)
-{
-	struct sp_node *n = sp_root(&r->used_regions), *p = NULL;
-	vm_t start = m->start;
-	enum sp_dir d = SP_LEFT;
-
-	m->sp_n = (struct sp_node){ 0 };
-
-	while (n) {
-		struct mem_region *t = mem_container(n);
-
-		p = n;
-
-		if (start < t->start) {
-			n = sp_left(n);
-			d = SP_LEFT;
-		}
-
-		else {
-			/* we should never encounter a situation where start =
-			 * t->start */
-			n = sp_right(n);
-			d = SP_RIGHT;
-		}
-	}
-
-	sp_insert(&sp_root(&r->used_regions), p, &m->sp_n, d);
-	return m;
-}
-
-stat_t init_region(struct mem_region_root *r, vm_t start, size_t arena_size)
-{
-	/* convert bytes to pages */
-	start = __page(start);
-	arena_size = __page(arena_size);
-	struct mem_region *m = get_mem_node();
-	m->start = start;
-	m->end = start + arena_size;
-	__insert_free_region(r, m);
-
-	return OK;
-}
-
-/**
- * Destroy memory region and all its children.
- *
- * @param n \ref sp_node of memory region to destroy.
- */
-static void __destroy_region(struct sp_node *n)
-{
-	if (!n)
-		return;
-
-	if (sp_left(n))
-		__destroy_region(sp_left(n));
-
-	if (sp_right(n))
-		__destroy_region(sp_right(n));
-
-	struct mem_region *m = mem_container(n);
-	free_mem_node(m);
-}
-
-stat_t destroy_region(struct mem_region_root *r)
-{
-	__destroy_region(sp_root(&r->free_regions));
-	__destroy_region(sp_root(&r->used_regions));
-	/** \todo error checking? */
-	return OK;
-}
-
-/* interestingly this is now the main bottleneck :D
- *
- * eh, it's not a massive thing I guess, maybe the code could be a bit quicker
- * but I mean 10 000 000 memory allocations in 20 s is good enough for now
- * */
-struct mem_region *find_used_region(struct mem_region_root *r, vm_t start)
-{
-	/** @todo check that start is aligned to page boundary? */
-	vm_t ref = __page(start);
-	struct sp_node *n = sp_root(&r->used_regions);
-	while (n) {
-		struct mem_region *t = mem_container(n);
-		if (ref == t->start)
-			return t;
-
-		if (ref < t->start)
-			n = sp_left(n);
-		else
-			n = sp_right(n);
-	}
-
-	return 0;
-}
-
-/**
- * Create memory region.
- *
- * @param start Start of region.
- * @param end End of region.
- * @param prev Previous region.
- * @param next Next region.
- * @return Created region.
- */
-static struct mem_region *__create_region(vm_t start, vm_t end,
-                                          struct mem_region *prev,
-                                          struct mem_region *next)
-{
-	struct mem_region *m = get_mem_node();
-	m->start = start;
-	m->end = end;
-	m->prev = prev;
-	m->next = next;
-	return m;
-}
-
-/**
- * Get first order size smaller than \c s in bytes.
- *
- * @param s Size to look for.
- * @return Size of first order smaller than \c s.
- */
-static size_t po_align(size_t s)
-{
-	for (size_t o = __mm_max_order; o > 0; --o) {
-		if (s >= order_size(o))
-			return order_size(o);
-	}
-
-	return 0;
-}
-
-struct mem_region *find_closest_used_region(struct mem_region_root *r,
-                                            vm_t start)
-{
-	struct mem_region *closest = 0;
-	size_t md = (size_t)(-1);
-	struct sp_node *n = sp_root(&r->used_regions);
-	if (!n)
-		return mem_container(sp_root(&r->free_regions));
-
-	while (n) {
-		struct mem_region *t = mem_container(n);
-		size_t d = ABS((ssize_t)start - (ssize_t)t->start);
-
-		if (d == 0) /* exact match */
-			return t;
-
-		if (d < md) { /* closest so far */
-			closest = t;
-			md = d;
-		}
-
-		if (start < t->start)
-			n = sp_left(n);
-		else
-			n = sp_right(n);
-	}
-
-	return closest;
-}
-
-/* should probably document this a bit better but in short, look for the "best"
- * free block, meaning one that is hopefully aligned so as to allow us to later
- * map it to higher order pages. If no block is found such that that is
- * possible, also keep track of the smallest block that we found that the region
- * still fits in, unaligned. If none of these criteria are met, a NULL is
- * returned. Note that this does not check *all* possible memory blocks, only
- * going up in increasing size so as to save time. */
-struct mem_region *find_free_region(struct mem_region_root *r, size_t size,
-                                    size_t *align)
-{
-	*align = 0;
-	size_t offset = __page(po_align(__addr(size)));
-	struct mem_region *quick_best = 0;
-	struct sp_node *n = sp_root(&r->free_regions);
-	while (n) {
-		struct mem_region *t = mem_container(n);
-		vm_t start = align_up(t->start, offset);
-
-		size_t qsize = t->end - t->start;
-		size_t bsize = t->end - start;
-
-		if (!quick_best && size <= qsize)
-			quick_best = t;
-
-		if (size <= bsize) {
-			*align = start - t->start;
-			return t;
-		}
-
-		n = sp_right(n);
-	}
-
-	return quick_best;
-}
-
-struct mem_region *find_first_region(struct mem_region_root *r)
-{
-	/* get used region with smallest address, likely also close to the start
-	 * of the linked list */
-	struct mem_region *m = find_closest_used_region(r, 0);
-	while (m->prev) {
-		m = m->prev;
-	}
-
-	return m;
-}
-
-/**
- * Carve out new used memory region from free memory region.
- *
- * @param r Memory region root to work in.
- * @param m Free memory region to carve used memory region out of.
- * @param pages Number of base order pages to give used region.
- * @param align Alignment of used region. In this case, start of used region
- * @param pid Process ID to associate with region if shared. 0 if private.
- * from start of free region.
- * @param flags Flags of used region.
- * @return Start address of used region.
- */
-static vm_t __partition_region(struct mem_region_root *r, struct mem_region *m,
-                               size_t pages, size_t align, vmflags_t flags,
-                               id_t pid)
-{
-	sp_remove(&sp_root(&r->free_regions), &m->sp_n);
-
-	vm_t pre_start = m->start;
-	vm_t pre_end = pre_start + align;
-
-	vm_t start = pre_end;
-	vm_t end = start + pages;
-
-	vm_t post_start = end;
-	vm_t post_end = m->end;
-
-	if (pre_start != pre_end) {
-		struct mem_region *n =
-			__create_region(pre_start, pre_end, m->prev, m);
-		m->prev = n;
-		if (n->prev)
-			n->prev->next = n;
-
-		__insert_free_region(r, n);
-	}
-
-	if (post_start != post_end) {
-		struct mem_region *n =
-			__create_region(post_start, post_end, m, m->next);
-		m->next = n;
-		if (n->next)
-			n->next->prev = n;
-
-		__insert_free_region(r, n);
-	}
-
-	m->end = end;
-	m->start = start;
-	m->flags = flags;
-	m->pid = pid;
-	mark_region_used(m->flags);
-	__insert_used_region(r, m);
-	return __addr(start);
-}
-
-/* apparently Linux doesn't necessarily give a shit about mmap hints, so I'll
- * just ignore them for now. Note that alloc_region should only be used when
- * mmap is called with MAP_ANON, all other situations should be handled in some
- * fs server */
-vm_t alloc_shared_region(struct mem_region_root *r, size_t size,
-                         size_t *actual_size,
-                         vmflags_t flags, id_t pid)
-{
-	size_t asize = align_up(size, BASE_PAGE_SIZE);
-	if (actual_size)
-		*actual_size = asize;
-
-	size_t pages = __page(asize);
-
-	/* find best fitting, alignment etc. */
-	size_t align = 0;
-	struct mem_region *m = find_free_region(r, pages, &align);
-	if (!m)
-		return 0;
-
-	return __partition_region(r, m, pages, align, flags, pid);
-}
-
-vm_t alloc_region(struct mem_region_root *r, size_t size, size_t *actual_size,
-                  vmflags_t flags)
-{
-	return alloc_shared_region(r, size, actual_size, flags, 0);
-}
-
-vm_t alloc_fixed_region(struct mem_region_root *r, vm_t start, size_t size,
-                        size_t *actual_size, vmflags_t flags)
-{
-	size_t asize = align_up(size, BASE_PAGE_SIZE);
-	if (actual_size)
-		*actual_size = asize;
-
-	size_t pages = __page(asize);
-	start = __page(start);
-
-	struct mem_region *m = find_closest_used_region(r, start);
-	if (!m)
-		return 0;
-
-	/* locate actual region where start is between the region start and end */
-	while (!((m->start <= start) && (start < m->end))) {
-		if (start > m->start)
-			m = m->next;
-		else
-			m = m->prev;
-	}
-
-	/* if region is already in use, forget it */
-	if (is_region_used(m))
-		return 0;
-
-	/* region is too small */
-	if (start + pages > m->end)
-		return 0;
-
-	/* actually start marking region used */
-	return __partition_region(r, m, pages, start - m->start, flags, 0);
-}
-
-/**
- * Try to coalesce two adjacent memory regions, iterating left.
- *
- * @param r Memory region root to work in.
- * @param m Memory region to start trying to coalesce.
- */
-static void __try_coalesce_prev(struct mem_region_root *r, struct mem_region *m)
-{
-	while (m) {
-		if (!m || is_region_used(m))
-			return;
-
-		struct mem_region *p = m->prev;
-		if (!p || is_region_used(p))
-			return;
-
-		m->start = p->start;
-		m->prev = p->prev;
-
-		if (m->prev)
-			m->prev->next = m;
-
-		sp_remove(&sp_root(&r->free_regions), &p->sp_n);
-		free_mem_node(p);
-
-		m = m->prev;
-	}
-}
-
-/**
- * Try to coalesce two adjacent memory region, iterating right.
- *
- * @param r Memory region root to work in.
- * @param m Memory region to start trying to coalesce.
- */
-static void __try_coalesce_next(struct mem_region_root *r, struct mem_region *m)
-{
-	while (m) {
-		if (!m || is_region_used(m))
-			return;
-
-		struct mem_region *n = m->next;
-		if (!n || is_region_used(n))
-			return;
-
-		m->end = n->end;
-		m->next = n->next;
-
-		if (m->next)
-			m->next->prev = m;
-
-		sp_remove(&sp_root(&r->free_regions), &n->sp_n);
-		free_mem_node(n);
-
-		m = m->next;
-	}
-}
-
-/**
- * Try coalescing memory regions.
- *
- * @param r Memory region root to work in.
- * @param m Memory region to start trying to coalesce.
- */
-static void __try_coalesce_regions(struct mem_region_root *r,
-                                   struct mem_region *m)
-{
-	__try_coalesce_prev(r, m);
-	__try_coalesce_next(r, m);
-}
-
-stat_t free_region(struct mem_region_root *r, vm_t start)
-{
-	/* addr not aligned to page boundary, corrupted or incorrect pointer */
-	if (!is_aligned(start, BASE_PAGE_SIZE))
-		return ERR_ALIGN;
-
-	struct mem_region *m = find_used_region(r, start);
-	if (!m)
-		return ERR_NF;
-
-	return free_known_region(r, m);
-}
-
-stat_t free_known_region(struct mem_region_root *r, struct mem_region *m)
-{
-	sp_remove(&sp_root(&r->used_regions), &m->sp_n);
-	mark_region_unused(m->flags);
-
-	__try_coalesce_regions(r, m);
-	__insert_free_region(r, m);
-	return OK;
-}
-
-void set_alt_region_addr(struct mem_region_root *r, vm_t va, vm_t alt_va)
-{
-	struct mem_region *m = find_used_region(r, va);
-	if (!m)
-		return;
-
-	/* not shared region */
-	if (m->pid == 0)
-		return;
-
-	m->alt_va = alt_va;
-}
-
-/* assuming start is chosen to start on an aligned border, this should choose
- * the 'optimal' fit for the mapping.
- *
- * NOTE: not actually optimal, this doesn't bother to go through possible
- * permutations etc. which would be slow and I don't want to implement it.
- */
-vm_t map_fill_region(struct vmem *b, region_callback_t *mem_handler,
-                     pm_t offset, vm_t start, size_t bytes, vmflags_t flags,
-                     void *data)
-{
-	pm_t runner = __page(start);
-	size_t pages = __pages(bytes);
-	enum mm_order top = __mm_max_order;
-
-	/* actual start might not be the same as the user specified start */
-	start = __addr(runner);
-
-	for (; pages; top--) {
-		size_t o_size = order_size(top);
-		size_t o_pages = __pages(o_size);
-
-		/* NULL does pass this check, so technically all NULL pages are
-		 * aligned, but they're caught in the while expr so this should
-		 * work even if someone tries to map NULL */
-		if (!is_aligned(runner, o_pages))
-			continue;
-
-		while (pages >= o_pages) {
-			stat_t res = mem_handler(b, &offset, __addr(runner),
-			                         flags, top, data);
-			if (res > 0)
-				break;
-
-			if (res < 0)
-				return 0;
-
-			pages -= o_pages;
-			runner += o_pages;
-		}
-	}
-
-	return start;
-}
-- 
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