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SubjectRe: [PATCH] proc-based cpu affinity user interface
I've been working on a patch that is a roll up of Andrew Morton's patch, and
also of some work by Nick Pollitt to use a prctl() interface to the
cpus_allowed bitmask. It also includes a new bitmask 'launch_policy' which
allows a process to set a launch policy which is used to determine it's
childrens' cpus_allowed bitmasks prior to launch.

The patch is against 2.4.10. It can be found on
http://sourceforge.com/projects/lse and I'll also attatch the most recent
version below.

Robert,
There are two reasons not to use the cpus_online_map.
1. It isn't (or at least wasn't as of 2.4.10) available on all architectures.
2. If cpus are added, or removed, the bitmask the user originally requested is
effectively ignored. ie: if the user tries to set cpus_allowed to 0x0000ffff
and we mask that against the current online map (0x00000003 in your example),
and then another cpu comes online, the cpus_allowed bitmask will not be updated
to reflect this change.

Ingo,
I'm going to look into using the set-affinity patch you posted with my patch.
I also agree that /proc is not the best way to access this data, but I *do*
believe it is *a* good way. I think that having both interfaces (/proc and a
syscall) gives us the best of both worlds.

Enjoy!

-matt

P.S.-please CC any replies, as I'm not on the list.diff -Nur linux-2.4.10/fs/proc/array.c linux-2.4.10-launch_policy/fs/proc/array.c
--- linux-2.4.10/fs/proc/array.c Fri Oct 26 15:07:16 2001
+++ linux-2.4.10-launch_policy/fs/proc/array.c Thu Nov 15 13:38:57 2001
@@ -50,6 +50,10 @@
* Al Viro & Jeff Garzik : moved most of the thing into base.c and
* : proc_misc.c. The rest may eventually go into
* : base.c too.
+ *
+ * Andrew Morton : cpus_allowed
+ *
+ * Matthew Dobson : launch_policy (Thanks to Andrew Morton for inspiraton)
*/

#include <linux/config.h>
@@ -343,7 +347,7 @@
read_unlock(&tasklist_lock);
res = sprintf(buffer,"%d (%s) %c %d %d %d %d %d %lu %lu \
%lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %lu %lu %ld %lu %lu %lu %lu %lu \
-%lu %lu %lu %lu %lu %lu %lu %lu %d %d\n",
+%lu %lu %lu %lu %lu %lu %lu %lu %d %d %lu %lu\n",
task->pid,
task->comm,
state,
@@ -386,7 +390,9 @@
task->nswap,
task->cnswap,
task->exit_signal,
- task->processor);
+ task->processor,
+ task->cpus_allowed,
+ task->launch_policy);
if(mm)
mmput(mm);
return res;
@@ -691,5 +697,62 @@
task->per_cpu_stime[cpu_logical_map(i)]);

return len;
+}
+
+static inline int proc_pid_cpu_bitmask_read(char * buffer, unsigned long *bitmask)
+{
+ int len;
+
+ len = sprintf(buffer, "%08lx\n", *bitmask);
+ return len;
+}
+
+/*
+ * FIXME: cpu_online_map should be used, but not all archs have it.
+ */
+
+static inline int proc_pid_cpu_bitmask_write(char * buffer, size_t nbytes, unsigned long *bitmask)
+{
+ unsigned long new_mask;
+ char *endp;
+ int ret;
+ unsigned long flags;
+
+ ret = -EPERM;
+ if (!capable(CAP_SYS_ADMIN))
+ goto out;
+
+ new_mask = simple_strtoul(buffer, &endp, 16);
+ ret = endp - buffer;
+
+ spin_lock_irqsave(&runqueue_lock, flags); /* token effort to not be racy */
+ if ((((1 << smp_num_cpus) - 1) & new_mask) == 0)
+ ret = -EINVAL;
+ else
+ *bitmask = new_mask;
+ spin_unlock_irqrestore(&runqueue_lock, flags);
+
+out:
+ return ret;
+}
+
+int proc_pid_cpus_allowed_read(struct task_struct *task, char * buffer)
+{
+ return proc_pid_cpu_bitmask_read(buffer, &task->cpus_allowed);
+}
+
+int proc_pid_cpus_allowed_write(struct task_struct *task, char * buffer, size_t nbytes)
+{
+ return proc_pid_cpu_bitmask_write(buffer, nbytes, &task->cpus_allowed);
+}
+
+int proc_pid_launch_policy_read(struct task_struct *task, char * buffer)
+{
+ return proc_pid_cpu_bitmask_read(buffer, &task->launch_policy);
+}
+
+int proc_pid_launch_policy_write(struct task_struct *task, char * buffer, size_t nbytes)
+{
+ return proc_pid_cpu_bitmask_write(buffer, nbytes, &task->launch_policy);
}
#endif
diff -Nur linux-2.4.10/fs/proc/base.c linux-2.4.10-launch_policy/fs/proc/base.c
--- linux-2.4.10/fs/proc/base.c Fri Oct 26 15:07:16 2001
+++ linux-2.4.10-launch_policy/fs/proc/base.c Fri Oct 19 15:42:15 2001
@@ -39,6 +39,10 @@
int proc_pid_status(struct task_struct*,char*);
int proc_pid_statm(struct task_struct*,char*);
int proc_pid_cpu(struct task_struct*,char*);
+int proc_pid_cpus_allowed_read(struct task_struct *task, char * buffer);
+int proc_pid_cpus_allowed_write(struct task_struct *task, char * buffer, size_t nbytes);
+int proc_pid_launch_policy_read(struct task_struct *task, char * buffer);
+int proc_pid_launch_policy_write(struct task_struct *task, char * buffer, size_t nbytes);

static int proc_fd_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
{
@@ -305,8 +309,44 @@
return count;
}

+static ssize_t proc_info_write(struct file * file, const char * buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode * inode = file->f_dentry->d_inode;
+ unsigned long page;
+ ssize_t ret;
+ struct task_struct *task = inode->u.proc_i.task;
+
+ ret = -EINVAL;
+ if (inode->u.proc_i.op.proc_write == NULL)
+ goto out;
+ if (count > PAGE_SIZE - 1)
+ goto out;
+
+ ret = -ENOMEM;
+ if (!(page = __get_free_page(GFP_KERNEL)))
+ goto out;
+
+ ret = -EFAULT;
+ if (copy_from_user((char *)page, buf, count))
+ goto out_free_page;
+
+ ((char *)page)[count] = '\0';
+ ret = inode->u.proc_i.op.proc_write(task, (char*)page, count);
+ if (ret < 0)
+ goto out_free_page;
+
+ *ppos += ret;
+
+out_free_page:
+ free_page(page);
+out:
+ return ret;
+}
+
static struct file_operations proc_info_file_operations = {
read: proc_info_read,
+ write: proc_info_write,
};

#define MAY_PTRACE(p) \
@@ -520,25 +560,29 @@
PROC_PID_STATM,
PROC_PID_MAPS,
PROC_PID_CPU,
+ PROC_PID_CPUS_ALLOWED,
+ PROC_PID_LAUNCH_POLICY,
PROC_PID_FD_DIR = 0x8000, /* 0x8000-0xffff */
};

#define E(type,name,mode) {(type),sizeof(name)-1,(name),(mode)}
static struct pid_entry base_stuff[] = {
- E(PROC_PID_FD, "fd", S_IFDIR|S_IRUSR|S_IXUSR),
- E(PROC_PID_ENVIRON, "environ", S_IFREG|S_IRUSR),
- E(PROC_PID_STATUS, "status", S_IFREG|S_IRUGO),
- E(PROC_PID_CMDLINE, "cmdline", S_IFREG|S_IRUGO),
- E(PROC_PID_STAT, "stat", S_IFREG|S_IRUGO),
- E(PROC_PID_STATM, "statm", S_IFREG|S_IRUGO),
+ E(PROC_PID_FD, "fd", S_IFDIR|S_IRUSR|S_IXUSR),
+ E(PROC_PID_ENVIRON, "environ", S_IFREG|S_IRUSR),
+ E(PROC_PID_STATUS, "status", S_IFREG|S_IRUGO),
+ E(PROC_PID_CMDLINE, "cmdline", S_IFREG|S_IRUGO),
+ E(PROC_PID_STAT, "stat", S_IFREG|S_IRUGO),
+ E(PROC_PID_STATM, "statm", S_IFREG|S_IRUGO),
#ifdef CONFIG_SMP
- E(PROC_PID_CPU, "cpu", S_IFREG|S_IRUGO),
+ E(PROC_PID_CPU, "cpu", S_IFREG|S_IRUGO),
+ E(PROC_PID_CPUS_ALLOWED, "cpus_allowed", S_IFREG|S_IRUGO|S_IWUSR),
+ E(PROC_PID_LAUNCH_POLICY, "launch_policy",S_IFREG|S_IRUGO|S_IWUSR),
#endif
- E(PROC_PID_MAPS, "maps", S_IFREG|S_IRUGO),
- E(PROC_PID_MEM, "mem", S_IFREG|S_IRUSR|S_IWUSR),
- E(PROC_PID_CWD, "cwd", S_IFLNK|S_IRWXUGO),
- E(PROC_PID_ROOT, "root", S_IFLNK|S_IRWXUGO),
- E(PROC_PID_EXE, "exe", S_IFLNK|S_IRWXUGO),
+ E(PROC_PID_MAPS, "maps", S_IFREG|S_IRUGO),
+ E(PROC_PID_MEM, "mem", S_IFREG|S_IRUSR|S_IWUSR),
+ E(PROC_PID_CWD, "cwd", S_IFLNK|S_IRWXUGO),
+ E(PROC_PID_ROOT, "root", S_IFLNK|S_IRWXUGO),
+ E(PROC_PID_EXE, "exe", S_IFLNK|S_IRWXUGO),
{0,0,NULL,0}
};
#undef E
@@ -892,6 +936,16 @@
case PROC_PID_CPU:
inode->i_fop = &proc_info_file_operations;
inode->u.proc_i.op.proc_read = proc_pid_cpu;
+ break;
+ case PROC_PID_CPUS_ALLOWED:
+ inode->i_fop = &proc_info_file_operations;
+ inode->u.proc_i.op.proc_read = proc_pid_cpus_allowed_read;
+ inode->u.proc_i.op.proc_write = proc_pid_cpus_allowed_write;
+ break;
+ case PROC_PID_LAUNCH_POLICY:
+ inode->i_fop = &proc_info_file_operations;
+ inode->u.proc_i.op.proc_read = proc_pid_launch_policy_read;
+ inode->u.proc_i.op.proc_write = proc_pid_launch_policy_write;
break;
#endif
case PROC_PID_MEM:
diff -Nur linux-2.4.10/include/linux/capability.h linux-2.4.10-launch_policy/include/linux/capability.h
--- linux-2.4.10/include/linux/capability.h Fri Oct 26 15:07:16 2001
+++ linux-2.4.10-launch_policy/include/linux/capability.h Mon Nov 19 15:27:40 2001
@@ -231,6 +231,8 @@
/* Allow enabling/disabling tagged queuing on SCSI controllers and sending
arbitrary SCSI commands */
/* Allow setting encryption key on loopback filesystem */
+/* Allow bonding of tasks to CPUs */
+/* Allow setting of launch policies */

#define CAP_SYS_ADMIN 21

diff -Nur linux-2.4.10/include/linux/prctl.h linux-2.4.10-launch_policy/include/linux/prctl.h
--- linux-2.4.10/include/linux/prctl.h Thu Jul 19 20:39:57 2001
+++ linux-2.4.10-launch_policy/include/linux/prctl.h Mon Nov 19 15:24:10 2001
@@ -20,4 +20,12 @@
#define PR_GET_KEEPCAPS 7
#define PR_SET_KEEPCAPS 8

+/* Get/set cpus allowed */
+#define PR_GET_CPUS_ALLOWED 13
+#define PR_SET_CPUS_ALLOWED 14
+
+/* Get/set launch policies */
+#define PR_GET_LAUNCH_POLICY 15
+#define PR_SET_LAUNCH_POLICY 16
+
#endif /* _LINUX_PRCTL_H */
diff -Nur linux-2.4.10/include/linux/proc_fs_i.h linux-2.4.10-launch_policy/include/linux/proc_fs_i.h
--- linux-2.4.10/include/linux/proc_fs_i.h Fri Oct 26 15:07:16 2001
+++ linux-2.4.10-launch_policy/include/linux/proc_fs_i.h Wed Oct 17 14:18:53 2001
@@ -1,9 +1,10 @@
struct proc_inode_info {
struct task_struct *task;
int type;
- union {
+ struct {
int (*proc_get_link)(struct inode *, struct dentry **, struct vfsmount **);
int (*proc_read)(struct task_struct *task, char *page);
+ int (*proc_write)(struct task_struct *task, char *page, size_t nbytes);
} op;
struct file *file;
};
diff -Nur linux-2.4.10/include/linux/sched.h linux-2.4.10-launch_policy/include/linux/sched.h
--- linux-2.4.10/include/linux/sched.h Sun Sep 23 10:31:02 2001
+++ linux-2.4.10-launch_policy/include/linux/sched.h Mon Nov 19 15:27:40 2001
@@ -344,6 +344,7 @@
struct task_struct *pidhash_next;
struct task_struct **pidhash_pprev;

+ unsigned long launch_policy; /* for *fork*() & exec() */
wait_queue_head_t wait_chldexit; /* for wait4() */
struct completion *vfork_done; /* for vfork() */
unsigned long rt_priority;
@@ -467,6 +468,7 @@
p_opptr: &tsk, \
p_pptr: &tsk, \
thread_group: LIST_HEAD_INIT(tsk.thread_group), \
+ launch_policy: -1, \
wait_chldexit: __WAIT_QUEUE_HEAD_INITIALIZER(tsk.wait_chldexit),\
real_timer: { \
function: it_real_fn \
diff -Nur linux-2.4.10/kernel/fork.c linux-2.4.10-launch_policy/kernel/fork.c
--- linux-2.4.10/kernel/fork.c Mon Sep 17 21:46:04 2001
+++ linux-2.4.10-launch_policy/kernel/fork.c Wed Oct 24 15:55:55 2001
@@ -646,6 +646,7 @@
spin_lock_init(&p->sigmask_lock);
}
#endif
+ p->cpus_allowed = p->launch_policy; /* launch_policy is inherited from parent */
p->lock_depth = -1; /* -1 = no lock */
p->start_time = jiffies;

diff -Nur linux-2.4.10/kernel/sys.c linux-2.4.10-launch_policy/kernel/sys.c
--- linux-2.4.10/kernel/sys.c Tue Sep 18 14:10:43 2001
+++ linux-2.4.10-launch_policy/kernel/sys.c Mon Nov 19 14:55:53 2001
@@ -1256,6 +1256,33 @@
}
current->keep_capabilities = arg2;
break;
+ case PR_GET_CPUS_ALLOWED:
+ error = put_user(current->cpus_allowed, (long *)arg2);
+ break;
+ case PR_SET_CPUS_ALLOWED:
+/*
+ * FIXME: cpu_online_map should be used, but not all archs have it.
+ */
+ if ((((1 << smp_num_cpus) - 1) & arg2) == 0)
+ error = -EINVAL;
+ else {
+ current->cpus_allowed = arg2;
+ if (!((1 << smp_processor_id()) & arg2))
+ current->need_resched = 1;
+ }
+ break;
+ case PR_GET_LAUNCH_POLICY:
+ error = put_user(current->launch_policy, (long *)arg2);
+ break;
+ case PR_SET_LAUNCH_POLICY:
+/*
+ * FIXME: cpu_online_map should be used, but not all archs have it.
+ */
+ if ((((1 << smp_num_cpus) - 1) & arg2) == 0)
+ error = -EINVAL;
+ else
+ current->launch_policy = arg2;
+ break;
default:
error = -EINVAL;
break;
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