From a3a51abfed4a8597e50f17e5398536d0be12cc75 Mon Sep 17 00:00:00 2001 From: Matheus Date: Sun, 7 Sep 2025 02:14:26 -0300 Subject: [PATCH] vmmcache: break down lock --- kernel-src/include/kernel/vfs.h | 2 + kernel-src/mm/vmmcache.c | 110 +++++++++++++++++++------------- 2 files changed, 66 insertions(+), 46 deletions(-) diff --git a/kernel-src/include/kernel/vfs.h b/kernel-src/include/kernel/vfs.h index c79769f8..6d3673be 100644 --- a/kernel-src/include/kernel/vfs.h +++ b/kernel-src/include/kernel/vfs.h @@ -103,6 +103,7 @@ typedef struct vnode_t { void *fifobinding; }; + mutex_t pages_mutex; struct page_t *pages; } vnode_t; @@ -162,6 +163,7 @@ typedef struct vops_t { (vn)->ops = o; \ MUTEX_INIT(&(vn)->lock); \ MUTEX_INIT(&(vn)->size_lock); \ + MUTEX_INIT(&(vn)->pages_mutex); \ (vn)->refcount = 1; \ (vn)->flags = f; \ (vn)->type = t; \ diff --git a/kernel-src/mm/vmmcache.c b/kernel-src/mm/vmmcache.c index 7da0f25e..26b32d69 100644 --- a/kernel-src/mm/vmmcache.c +++ b/kernel-src/mm/vmmcache.c @@ -9,7 +9,7 @@ #define TABLE_SIZE 4096 #define WRITER_TICK_SECONDS 15 -static mutex_t mutex; +static mutex_t *mutex_table; static page_t **table; static thread_t *writerthread; @@ -18,11 +18,11 @@ static eventheader_t syncevent; static eventheader_t pagereadyevent; size_t vmmcache_cachedpages; -#define HOLD_LOCK() \ - MUTEX_ACQUIRE(&mutex); +#define HOLD_LOCK(vnode, offset) \ + MUTEX_ACQUIRE(&mutex_table[getentry(vnode, offset)]); -#define RELEASE_LOCK() \ - MUTEX_RELEASE(&mutex); +#define RELEASE_LOCK(vnode, offset) \ + MUTEX_RELEASE(&mutex_table[getentry(vnode, offset)]); static inline uint64_t fnv1ahash(void *buffer, size_t size); static uintmax_t getentry(vnode_t *vnode, uintmax_t offset) { @@ -70,7 +70,7 @@ static void putpage(page_t *page) { page->backing->pages->vnodeprev = page; page->backing->pages = page; - ++vmmcache_cachedpages; + __atomic_fetch_add(&vmmcache_cachedpages, 1, __ATOMIC_SEQ_CST); } // assumes lock is held @@ -100,14 +100,14 @@ static void removepage(page_t *page) { page->vnodenext = NULL; page->vnodeprev = NULL; - --vmmcache_cachedpages; + __atomic_fetch_sub(&vmmcache_cachedpages, 1, __ATOMIC_SEQ_CST); } int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { __assert(vnode->type == V_TYPE_REGULAR || vnode->type == V_TYPE_BLKDEV); __assert((offset % PAGE_SIZE) == 0); retry_err: - HOLD_LOCK(); + HOLD_LOCK(vnode, offset); page_t *newpage = NULL; volatile page_t *page = findpage(vnode, offset); @@ -115,7 +115,7 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { if (page) { // page is present in the page cache pmm_hold(pmm_getpageaddress((page_t *)page)); - RELEASE_LOCK(); + RELEASE_LOCK(vnode, offset); // in the case of a retry, release the allocated page here if (newpage) @@ -140,7 +140,7 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { *res = (page_t *)page; } else { // page is not present in the cache, we will have to load it in - RELEASE_LOCK(); + RELEASE_LOCK(vnode, offset); void *address = pmm_allocpage(PMM_SECTION_DEFAULT); if (address == NULL) @@ -148,13 +148,16 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { newpage = pmm_getpage(address); - HOLD_LOCK(); + MUTEX_ACQUIRE(&vnode->pages_mutex); + HOLD_LOCK(vnode, offset); // while the lock wasn't being held, the page could have potentially been added to the cache // check for it again and return from the function as if it was always there in the first place page = findpage(vnode, offset); - if (page) + if (page) { + MUTEX_RELEASE(&vnode->pages_mutex); goto retry; + } newpage->backing = vnode; newpage->offset = offset; @@ -162,7 +165,8 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { // add it to the page cache putpage(newpage); - RELEASE_LOCK(); + MUTEX_RELEASE(&vnode->pages_mutex); + RELEASE_LOCK(vnode, offset); VOP_LOCK(vnode); int error = VOP_GETPAGE(vnode, offset, newpage); @@ -172,14 +176,16 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { // an error happened with GETPAGE, remove the page from the cache, // tell the sleeping threads that something happened and free the page // by setting backing to null so it gets treated as an anonymous page again - HOLD_LOCK(); + MUTEX_ACQUIRE(&vnode->pages_mutex); + HOLD_LOCK(vnode, offset); removepage(newpage); + MUTEX_RELEASE(&vnode->pages_mutex); newpage->flags |= PAGE_FLAGS_ERROR; newpage->backing = NULL; newpage->offset = 0; - RELEASE_LOCK(); + RELEASE_LOCK(vnode, offset); pmm_release(pmm_getpageaddress(newpage)); EVENT_SIGNAL(&pagereadyevent); return error; @@ -196,11 +202,13 @@ int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) { // adds a page to the cache in a specific offset if its not already there int vmmcache_pushpage(vnode_t *vnode, uintmax_t offset, page_t *page) { __assert((offset % PAGE_SIZE) == 0); - HOLD_LOCK(); + MUTEX_ACQUIRE(&vnode->pages_mutex); + HOLD_LOCK(vnode, offset); page_t *pagetest = findpage(vnode, offset); if (pagetest) { - RELEASE_LOCK(); + MUTEX_RELEASE(&vnode->pages_mutex); + RELEASE_LOCK(vnode, offset); return EAGAIN; } @@ -210,15 +218,18 @@ int vmmcache_pushpage(vnode_t *vnode, uintmax_t offset, page_t *page) { putpage(page); - RELEASE_LOCK(); + MUTEX_RELEASE(&vnode->pages_mutex); + RELEASE_LOCK(vnode, offset); return 0; } // removes a page from the cache AND turns it into anonymous memory int vmmcache_evict(page_t *page) { - HOLD_LOCK(); + MUTEX_ACQUIRE(&page->backing->pages_mutex); + HOLD_LOCK(page->backing, page->offset); if (page->refcount > 1) { - RELEASE_LOCK(); + MUTEX_RELEASE(&page->backing->pages_mutex); + RELEASE_LOCK(page->backing, page->offset); return EAGAIN; } __assert(page->refcount == 1); @@ -229,21 +240,24 @@ int vmmcache_evict(page_t *page) { removepage(page); } + MUTEX_RELEASE(&page->backing->pages_mutex); + RELEASE_LOCK(page->backing, page->offset); + page->flags = 0; page->backing = NULL; page->offset = 0; - - RELEASE_LOCK(); return 0; } // removes a page from the cache *but doesn't do anything to it* int vmmcache_takepage(page_t *page) { - HOLD_LOCK(); + MUTEX_ACQUIRE(&page->backing->pages_mutex); + HOLD_LOCK(page->backing, page->offset); // someone called vmmcache_getpage() and got this page while the lock wasn't held // return an error status to the caller if (page->refcount > 1) { - RELEASE_LOCK(); + MUTEX_RELEASE(&page->backing->pages_mutex); + RELEASE_LOCK(page->backing, page->offset); return EAGAIN; } @@ -256,12 +270,13 @@ int vmmcache_takepage(page_t *page) { removepage(page); } - RELEASE_LOCK(); + MUTEX_RELEASE(&page->backing->pages_mutex); + RELEASE_LOCK(page->backing, page->offset); return 0; } int vmmcache_truncate(vnode_t *vnode, uintmax_t offset) { - HOLD_LOCK(); + MUTEX_ACQUIRE(&vnode->pages_mutex); page_t *pagelist = NULL; page_t *page = vnode->pages; @@ -273,13 +288,16 @@ int vmmcache_truncate(vnode_t *vnode, uintmax_t offset) { if (oldpage->offset < offset) continue; - oldpage->flags |= PAGE_FLAGS_TRUNCATED; + __atomic_or_fetch(&oldpage->flags, PAGE_FLAGS_TRUNCATED, __ATOMIC_SEQ_CST); + HOLD_LOCK(oldpage->backing, oldpage->offset); removepage(oldpage); + RELEASE_LOCK(oldpage->backing, oldpage->offset); + oldpage->vnodenext = pagelist; pagelist = oldpage; } - RELEASE_LOCK(); + MUTEX_RELEASE(&vnode->pages_mutex); // make sure to unref if they are pinned while (pagelist) { @@ -292,15 +310,11 @@ int vmmcache_truncate(vnode_t *vnode, uintmax_t offset) { return 0; } -// called with lock held -// returns with lock released -// expects backing lock to be held static int syncpage(page_t *page, bool backinglock) { - __assert(page->flags & PAGE_FLAGS_DIRTY); - page->flags &= ~PAGE_FLAGS_DIRTY; - RELEASE_LOCK(); + int flags = __atomic_fetch_and(&page->flags, ~PAGE_FLAGS_DIRTY, __ATOMIC_SEQ_CST); + __assert(flags & PAGE_FLAGS_DIRTY); int e = 0; - if ((page->flags & PAGE_FLAGS_TRUNCATED) == 0) { + if ((flags & PAGE_FLAGS_TRUNCATED) == 0) { if (backinglock) VOP_LOCK(page->backing); @@ -319,6 +333,7 @@ static int syncpage(page_t *page, bool backinglock) { return e; } +MUTEX_DEFINE(dirty_list_mutex); static page_t *dirtylist; static page_t *dirtylistend; @@ -328,7 +343,8 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) { uintmax_t top = offset + size; // overflow check __assert(top > offset); - HOLD_LOCK(); + MUTEX_ACQUIRE(&vnode->pages_mutex); + MUTEX_ACQUIRE(&dirty_list_mutex); // loop through all vnode pages in memory and check which ones are in the range and are dirty // TODO create a proper vnode dirty list as to not have to loop through the ENTIRE thing in memory @@ -356,13 +372,13 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) { vnodedirtylist = page; } - RELEASE_LOCK(); + MUTEX_RELEASE(&dirty_list_mutex); + MUTEX_RELEASE(&vnode->pages_mutex); int e = 0; while (vnodedirtylist) { // in the case of failure, only the first error to occur will be reported and we will not // retry the write and keep on syncing the pages to disk - HOLD_LOCK(); page_t *page = vnodedirtylist; vnodedirtylist = vnodedirtylist->writenext; page->writenext = NULL; @@ -380,16 +396,13 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) { int vmmcache_sync() { eventlistener_t eventlistener; EVENT_INITLISTENER(&eventlistener); - HOLD_LOCK(); if (dirtylist == NULL) { // no dirty pages - RELEASE_LOCK(); return 0; } EVENT_ATTACH(&eventlistener, &syncevent); semaphore_signal(&sync); - RELEASE_LOCK(); EVENT_WAIT(&eventlistener, 0); @@ -400,7 +413,7 @@ int vmmcache_sync() { // backing expected locked int vmmcache_makedirty(page_t *page) { bool madedirty = false; - HOLD_LOCK(); + MUTEX_ACQUIRE(&dirty_list_mutex); if ((page->flags & (PAGE_FLAGS_DIRTY | PAGE_FLAGS_TRUNCATED)) == 0) { madedirty = true; @@ -420,7 +433,7 @@ int vmmcache_makedirty(page_t *page) { VOP_HOLD(page->backing); } - RELEASE_LOCK(); + MUTEX_RELEASE(&dirty_list_mutex); if (madedirty) { vattr_t attr; attr.mtime = timekeeper_time(); @@ -440,11 +453,11 @@ static void writer() { timer_insert(current_cpu()->timer, &timerentry, tick, NULL, (uintmax_t)WRITER_TICK_SECONDS * 1000000, true); interrupt_set(true); for (;;) { - HOLD_LOCK(); + MUTEX_ACQUIRE(&dirty_list_mutex); volatile page_t *page = dirtylistend; if (page == NULL) { + MUTEX_RELEASE(&dirty_list_mutex); EVENT_SIGNAL(&syncevent); - RELEASE_LOCK(); semaphore_wait(&sync, false); continue; } @@ -456,16 +469,21 @@ static void writer() { dirtylist = NULL; page->writeprev = NULL; + MUTEX_RELEASE(&dirty_list_mutex); + // TODO notify error on vmmcache_syncvnode syncpage((page_t *)page, true); } } void vmmcache_init() { - MUTEX_INIT(&mutex); table = vmm_map(NULL, TABLE_SIZE * sizeof(page_t *), VMM_FLAGS_ALLOCATE, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC, NULL); __assert(table); + mutex_table = vmm_map(NULL, TABLE_SIZE * sizeof(mutex_t), VMM_FLAGS_ALLOCATE, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC, NULL); + __assert(mutex_table); memset(table, 0, TABLE_SIZE * sizeof(page_t *)); + for (int i = 0; i < TABLE_SIZE; ++i) + MUTEX_INIT(&mutex_table[i]); SEMAPHORE_INIT(&sync, 0); writerthread = sched_newthread(writer, PAGE_SIZE * 16, 1, NULL, NULL);