From 39743889aaf76725152f16aa90ca3c45f6d52da3 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sun, 8 Jan 2006 01:00:51 -0800 Subject: [PATCH] Swap Migration V5: sys_migrate_pages interface sys_migrate_pages implementation using swap based page migration This is the original API proposed by Ray Bryant in his posts during the first half of 2005 on linux-mm@kvack.org and linux-kernel@vger.kernel.org. The intent of sys_migrate is to migrate memory of a process. A process may have migrated to another node. Memory was allocated optimally for the prior context. sys_migrate_pages allows to shift the memory to the new node. sys_migrate_pages is also useful if the processes available memory nodes have changed through cpuset operations to manually move the processes memory. Paul Jackson is working on an automated mechanism that will allow an automatic migration if the cpuset of a process is changed. However, a user may decide to manually control the migration. This implementation is put into the policy layer since it uses concepts and functions that are also needed for mbind and friends. The patch also provides a do_migrate_pages function that may be useful for cpusets to automatically move memory. sys_migrate_pages does not modify policies in contrast to Ray's implementation. The current code here is based on the swap based page migration capability and thus is not able to preserve the physical layout relative to it containing nodeset (which may be a cpuset). When direct page migration becomes available then the implementation needs to be changed to do a isomorphic move of pages between different nodesets. The current implementation simply evicts all pages in source nodeset that are not in the target nodeset. Patch supports ia64, i386 and x86_64. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempolicy.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 93 insertions(+), 1 deletion(-) (limited to 'mm/mempolicy.c') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 9cc6d96..20d5ad3 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -615,11 +615,41 @@ long do_get_mempolicy(int *policy, nodemask_t *nmask, } /* + * For now migrate_pages simply swaps out the pages from nodes that are in + * the source set but not in the target set. In the future, we would + * want a function that moves pages between the two nodesets in such + * a way as to preserve the physical layout as much as possible. + * + * Returns the number of page that could not be moved. + */ +int do_migrate_pages(struct mm_struct *mm, + const nodemask_t *from_nodes, const nodemask_t *to_nodes, int flags) +{ + LIST_HEAD(pagelist); + int count = 0; + nodemask_t nodes; + + nodes_andnot(nodes, *from_nodes, *to_nodes); + nodes_complement(nodes, nodes); + + down_read(&mm->mmap_sem); + check_range(mm, mm->mmap->vm_start, TASK_SIZE, &nodes, + flags | MPOL_MF_DISCONTIG_OK, &pagelist); + if (!list_empty(&pagelist)) { + migrate_pages(&pagelist, NULL); + if (!list_empty(&pagelist)) + count = putback_lru_pages(&pagelist); + } + up_read(&mm->mmap_sem); + return count; +} + +/* * User space interface with variable sized bitmaps for nodelists. */ /* Copy a node mask from user space. */ -static int get_nodes(nodemask_t *nodes, unsigned long __user *nmask, +static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask, unsigned long maxnode) { unsigned long k; @@ -708,6 +738,68 @@ asmlinkage long sys_set_mempolicy(int mode, unsigned long __user *nmask, return do_set_mempolicy(mode, &nodes); } +/* Macro needed until Paul implements this function in kernel/cpusets.c */ +#define cpuset_mems_allowed(task) node_online_map + +asmlinkage long sys_migrate_pages(pid_t pid, unsigned long maxnode, + const unsigned long __user *old_nodes, + const unsigned long __user *new_nodes) +{ + struct mm_struct *mm; + struct task_struct *task; + nodemask_t old; + nodemask_t new; + nodemask_t task_nodes; + int err; + + err = get_nodes(&old, old_nodes, maxnode); + if (err) + return err; + + err = get_nodes(&new, new_nodes, maxnode); + if (err) + return err; + + /* Find the mm_struct */ + read_lock(&tasklist_lock); + task = pid ? find_task_by_pid(pid) : current; + if (!task) { + read_unlock(&tasklist_lock); + return -ESRCH; + } + mm = get_task_mm(task); + read_unlock(&tasklist_lock); + + if (!mm) + return -EINVAL; + + /* + * Check if this process has the right to modify the specified + * process. The right exists if the process has administrative + * capabilities, superuser priviledges or the same + * userid as the target process. + */ + if ((current->euid != task->suid) && (current->euid != task->uid) && + (current->uid != task->suid) && (current->uid != task->uid) && + !capable(CAP_SYS_ADMIN)) { + err = -EPERM; + goto out; + } + + task_nodes = cpuset_mems_allowed(task); + /* Is the user allowed to access the target nodes? */ + if (!nodes_subset(new, task_nodes) && !capable(CAP_SYS_ADMIN)) { + err = -EPERM; + goto out; + } + + err = do_migrate_pages(mm, &old, &new, MPOL_MF_MOVE); +out: + mmput(mm); + return err; +} + + /* Retrieve NUMA policy */ asmlinkage long sys_get_mempolicy(int __user *policy, unsigned long __user *nmask, -- cgit v1.1