1021.lowlatency.patch

sm86xx内核源包括补丁（ GPL ）的

 {
 	struct list_head *curr;
 	struct page * page;
@@ -271,6 +281,17 @@
 	while (curr != head) {
 		unsigned long offset;
 
+		if (conditional_schedule_needed() && *restart_count) {
+			(*restart_count)--;
+			list_del(head);
+			list_add(head, curr);		/* Restart on this page */
+			spin_unlock(&pagecache_lock);
+			unconditional_schedule();
+			spin_lock(&pagecache_lock);
+			unlocked = 1;
+			goto restart;
+		}
+
 		page = list_entry(curr, struct page, list);
 		offset = page->index;
 
@@ -303,13 +324,11 @@
 			} else
  				wait_on_page(page);
 
-			page_cache_release(page);
-
-			if (current->need_resched) {
-				__set_current_state(TASK_RUNNING);
-				schedule();
+			if (LOWLATENCY_NEEDED) {
+				*restart_count = 4;	/* We made progress */
 			}
 
+			page_cache_release(page);
 			spin_lock(&pagecache_lock);
 			goto restart;
 		}
@@ -332,13 +351,14 @@
 {
 	unsigned long start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 	unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
+	int restart_count = 4;
 	int unlocked;
 
 	spin_lock(&pagecache_lock);
 	do {
-		unlocked = truncate_list_pages(&mapping->clean_pages, start, &partial);
-		unlocked |= truncate_list_pages(&mapping->dirty_pages, start, &partial);
-		unlocked |= truncate_list_pages(&mapping->locked_pages, start, &partial);
+		unlocked = truncate_list_pages(&mapping->clean_pages, start, &partial, &restart_count);
+		unlocked |= truncate_list_pages(&mapping->dirty_pages, start, &partial, &restart_count);
+		unlocked |= truncate_list_pages(&mapping->locked_pages, start, &partial, &restart_count);
 	} while (unlocked);
 	/* Traversed all three lists without dropping the lock */
 	spin_unlock(&pagecache_lock);
@@ -483,6 +503,7 @@
 
 		page_cache_get(page);
 		spin_unlock(&pagecache_lock);
+		conditional_schedule();		/* sys_msync() (only used by minixfs, udf) */
 		lock_page(page);
 
 		/* The buffers could have been free'd while we waited for the page lock */
@@ -612,12 +633,14 @@
 		list_del(&page->list);
 		list_add(&page->list, &mapping->locked_pages);
 
-		if (!PageDirty(page))
-			continue;
-
 		page_cache_get(page);
 		spin_unlock(&pagecache_lock);
 
+		conditional_schedule();		/* sys_msync() */
+
+		if (!PageDirty(page))
+			goto clean;
+
 		lock_page(page);
 
 		if (PageDirty(page)) {
@@ -628,7 +651,7 @@
 				ret = err;
 		} else
 			UnlockPage(page);
-
+clean:
 		page_cache_release(page);
 		spin_lock(&pagecache_lock);
 	}
@@ -646,7 +669,8 @@
 int filemap_fdatawait(struct address_space * mapping)
 {
 	int ret = 0;
-
+	DEFINE_RESCHED_COUNT;
+restart:
 	spin_lock(&pagecache_lock);
 
         while (!list_empty(&mapping->locked_pages)) {
@@ -655,6 +679,17 @@
 		list_del(&page->list);
 		list_add(&page->list, &mapping->clean_pages);
 
+		if (TEST_RESCHED_COUNT(32)) {
+			RESET_RESCHED_COUNT();
+			if (conditional_schedule_needed()) {
+				page_cache_get(page);
+				spin_unlock(&pagecache_lock);
+				unconditional_schedule();
+				page_cache_release(page);
+				goto restart;
+			}
+		}
+
 		if (!PageLocked(page))
 			continue;
 
@@ -764,8 +799,10 @@
 	spin_lock(&pagecache_lock);
 	page = __find_page_nolock(mapping, offset, *hash);
 	spin_unlock(&pagecache_lock);
-	if (page)
+	if (page) {
+		conditional_schedule();
 		return 0;
+	}
 
 	page = page_cache_alloc(mapping);
 	if (!page)
@@ -1035,6 +1072,11 @@
 	 * the hash-list needs a held write-lock.
 	 */
 repeat:
+	if (conditional_schedule_needed()) {
+		spin_unlock(&pagecache_lock);
+		unconditional_schedule();
+		spin_lock(&pagecache_lock);
+	}
 	page = __find_page_nolock(mapping, offset, hash);
 	if (page) {
 		page_cache_get(page);
@@ -1488,6 +1530,8 @@
 		page_cache_get(page);
 		spin_unlock(&pagecache_lock);
 
+		conditional_schedule();		/* sys_read() */
+
 		if (!Page_Uptodate(page))
 			goto page_not_up_to_date;
 		generic_file_readahead(reada_ok, filp, inode, page);
@@ -2247,6 +2291,12 @@
 		address += PAGE_SIZE;
 		pte++;
 	} while (address && (address < end));
+
+	if (conditional_schedule_needed()) {
+		spin_unlock(&vma->vm_mm->page_table_lock);
+		unconditional_schedule();		/* syncing large mapped files */
+		spin_lock(&vma->vm_mm->page_table_lock);
+	}
 	return error;
 }
 
@@ -2656,7 +2706,9 @@
 	if (vma->vm_flags & VM_LOCKED)
 		return -EINVAL;
 
-	zap_page_range(vma->vm_mm, start, end - start);
+        zap_page_range(vma->vm_mm, start, end - start,
+		ZPR_COND_RESCHED);        /* sys_madvise(MADV_DONTNEED) */
+
 	return 0;
 }
 
@@ -3226,6 +3278,9 @@
 			goto sync_failure;
 		page_fault = __copy_from_user(kaddr+offset, buf, bytes);
 		flush_dcache_page(page);
+
+                conditional_schedule();
+
 		status = mapping->a_ops->commit_write(file, page, offset, offset+bytes);
 		if (page_fault)
 			goto fail_write;
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/mm/memory.c linuxmips-2.4.30/mm/memory.c
--- linuxmips-2.4.30.ref/mm/memory.c	2005-04-05 12:09:58.000000000 -0700
+++ linuxmips-2.4.30/mm/memory.c	2005-07-22 09:36:02.000000000 -0700
@@ -357,7 +357,7 @@
 /*
  * remove user pages in a given range.
  */
-void zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long size)
+static void do_zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long size)
 {
 	mmu_gather_t *tlb;
 	pgd_t * dir;
@@ -478,6 +478,10 @@
 			struct page *map;
 			while (!(map = follow_page(mm, start, write))) {
 				spin_unlock(&mm->page_table_lock);
+
+				/* Pinning down many physical pages (kiobufs, mlockall) */
+				conditional_schedule();
+
 				switch (handle_mm_fault(mm, vma, start, write)) {
 				case 1:
 					tsk->min_flt++;
@@ -641,6 +645,21 @@
 	iobuf->locked = 0;
 }
 
+#define MAX_ZAP_BYTES 256*PAGE_SIZE
+
+void zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long size, int actions)
+{
+	while (size) {
+		unsigned long chunk = size;
+		if (actions & ZPR_COND_RESCHED && chunk > MAX_ZAP_BYTES)
+			chunk = MAX_ZAP_BYTES;
+		do_zap_page_range(mm, address, chunk);
+		if (actions & ZPR_COND_RESCHED)
+			conditional_schedule();
+		address += chunk;
+		size -= chunk;
+	}
+}
 
 /*
  * Lock down all of the pages of a kiovec for IO.
@@ -750,11 +769,18 @@
 	return 0;
 }
 
-static inline void zeromap_pte_range(pte_t * pte, unsigned long address,
-                                     unsigned long size, pgprot_t prot)
+static inline void zeromap_pte_range(struct mm_struct *mm, pte_t * pte,
+				unsigned long address, unsigned long size,
+				pgprot_t prot)
 {
 	unsigned long end;
 
+	if (conditional_schedule_needed()) {
+		spin_unlock(&mm->page_table_lock);
+		unconditional_schedule();		/* mmap(/dev/zero) */
+		spin_lock(&mm->page_table_lock);
+	}
+
 	address &= ~PMD_MASK;
 	end = address + size;
 	if (end > PMD_SIZE)
@@ -782,7 +808,7 @@
 		pte_t * pte = pte_alloc(mm, pmd, address);
 		if (!pte)
 			return -ENOMEM;
-		zeromap_pte_range(pte, address, end - address, prot);
+		zeromap_pte_range(mm, pte, address, end - address, prot);
 		address = (address + PMD_SIZE) & PMD_MASK;
 		pmd++;
 	} while (address && (address < end));
@@ -1017,7 +1043,7 @@
 
 		/* mapping wholly truncated? */
 		if (mpnt->vm_pgoff >= pgoff) {
-			zap_page_range(mm, start, len);
+                        zap_page_range(mm, start, len, 0);
 			continue;
 		}
 
@@ -1030,7 +1056,7 @@
 		/* Ok, partially affected.. */
 		start += diff << PAGE_SHIFT;
 		len = (len - diff) << PAGE_SHIFT;
-		zap_page_range(mm, start, len);
+                zap_page_range(mm, start, len, 0);
 	} while ((mpnt = mpnt->vm_next_share) != NULL);
 }
 
diff -Naur --exclude=CVS --exclude='*.o' --exclude='*.a' --exclude='*.so' --exclude='*.elf' --exclude=System.map --exclude=Makefile.d --exclude='*log' --exclude='*log2' --exclude='*~' --exclude='.*~' --exclude='.#*' --exclude='*.bak' --exclude='*.orig' --exclude='*.rej' --exclude='core.[0-9]*' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=.depend --exclude='.*.o.flags' --exclude='*.gz' --exclude=vmlinux --exclude=vmlinux.bin --exclude=yamon-02.06-SIGMADESIGNS-01_el.bin linuxmips-2.4.30.ref/mm/mmap.c linuxmips-2.4.30/mm/mmap.c
--- linuxmips-2.4.30.ref/mm/mmap.c	2005-01-13 02:59:04.000000000 -0800
+++ linuxmips-2.4.30/mm/mmap.c	2005-07-22 09:36:02.000000000 -0700
@@ -600,7 +600,7 @@
 	fput(file);
 
 	/* Undo any partial mapping done by a device driver. */
-	zap_page_range(mm, vma->vm_start, vma->vm_end - vma->vm_start);
+        zap_page_range(mm, vma->vm_start, vma->vm_end - vma->vm_start, 0);
 free_vma:
 	kmem_cache_free(vm_area_cachep, vma);
 	return error;
@@ -1000,7 +1000,7 @@
 		remove_shared_vm_struct(mpnt);
 		mm->map_count--;
 
-		zap_page_range(mm, st, size);
+                zap_page_range(mm, st, size, ZPR_COND_RESCHED);   /* sys_munmap() */
 
 		/*
 		 * Fix the mapping, and free the old area if it wasn't reused.
@@ -1175,7 +1175,7 @@
 		}
 		mm->map_count--;
 		remove_shared_vm_struct(mpnt);
-		zap_page_range(mm, start, size);
+		zap_page_range(mm, start, size, ZPR_COND_RESCHED);      /* sys_exit() */
 		if (mp