The task still allocated the page caches on old node after modifying its
cpuset's mems when 'memory_spread_page' was set, it is caused by the old
mem_allowed_list of the task, the current kernel doesn't updates it unless some
function invokes cpuset_update_task_memory_state(), it is too late sometimes.
We must update the mem_allowed_list of the tasks in time.
Slab has the same problem.
We fixes the bug by updating tasks' mem_allowed_list and spread flag after
its cpuset's mems or spread flag is changed.
Signed-off-by: Miao Xie <[email protected]>
---
include/linux/cpuset.h | 4 -
include/linux/sched.h | 1 -
init/main.c | 3 +-
kernel/cpuset.c | 204 +++++++++++++++--------------------------------
kernel/kthread.c | 1 +
mm/mempolicy.c | 12 ---
mm/page_alloc.c | 5 +-
7 files changed, 69 insertions(+), 161 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 90c6074..c8155a6 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,7 +17,6 @@
extern int number_of_cpusets; /* How many cpusets are defined in system? */
-extern int cpuset_init_early(void);
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
@@ -26,7 +25,6 @@ extern void cpuset_cpus_allowed_locked(struct task_struct *p,
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
#define cpuset_current_mems_allowed (current->mems_allowed)
void cpuset_init_current_mems_allowed(void);
-void cpuset_update_task_memory_state(void);
int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask);
extern int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask);
@@ -83,7 +81,6 @@ extern void cpuset_print_task_mems_allowed(struct task_struct *p);
#else /* !CONFIG_CPUSETS */
-static inline int cpuset_init_early(void) { return 0; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
@@ -105,7 +102,6 @@ static inline nodemask_t cpuset_mems_allowed(struct task_struct *p)
#define cpuset_current_mems_allowed (node_states[N_HIGH_MEMORY])
static inline void cpuset_init_current_mems_allowed(void) {}
-static inline void cpuset_update_task_memory_state(void) {}
static inline int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
{
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4cae9b8..2c9a93c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1332,7 +1332,6 @@ struct task_struct {
#endif
#ifdef CONFIG_CPUSETS
nodemask_t mems_allowed;
- int cpuset_mems_generation;
int cpuset_mem_spread_rotor;
#endif
#ifdef CONFIG_CGROUPS
diff --git a/init/main.c b/init/main.c
index 8442094..3ce3b5d 100644
--- a/init/main.c
+++ b/init/main.c
@@ -635,7 +635,6 @@ asmlinkage void __init start_kernel(void)
#endif
vmalloc_init();
vfs_caches_init_early();
- cpuset_init_early();
page_cgroup_init();
mem_init();
enable_debug_pagealloc();
@@ -845,6 +844,8 @@ static int __init kernel_init(void * unused)
*/
init_pid_ns.child_reaper = current;
+ current->mems_allowed = node_possible_map;
+
cad_pid = task_pid(current);
smp_prepare_cpus(setup_max_cpus);
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index a856788..36436fc 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -89,12 +89,6 @@ struct cpuset {
struct cpuset *parent; /* my parent */
- /*
- * Copy of global cpuset_mems_generation as of the most
- * recent time this cpuset changed its mems_allowed.
- */
- int mems_generation;
-
struct fmeter fmeter; /* memory_pressure filter */
/* partition number for rebuild_sched_domains() */
@@ -172,27 +166,6 @@ static inline int is_spread_slab(const struct cpuset *cs)
return test_bit(CS_SPREAD_SLAB, &cs->flags);
}
-/*
- * Increment this integer everytime any cpuset changes its
- * mems_allowed value. Users of cpusets can track this generation
- * number, and avoid having to lock and reload mems_allowed unless
- * the cpuset they're using changes generation.
- *
- * A single, global generation is needed because cpuset_attach_task() could
- * reattach a task to a different cpuset, which must not have its
- * generation numbers aliased with those of that tasks previous cpuset.
- *
- * Generations are needed for mems_allowed because one task cannot
- * modify another's memory placement. So we must enable every task,
- * on every visit to __alloc_pages(), to efficiently check whether
- * its current->cpuset->mems_allowed has changed, requiring an update
- * of its current->mems_allowed.
- *
- * Since writes to cpuset_mems_generation are guarded by the cgroup lock
- * there is no need to mark it atomic.
- */
-static int cpuset_mems_generation;
-
static struct cpuset top_cpuset = {
.flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
};
@@ -224,8 +197,8 @@ static struct cpuset top_cpuset = {
* If a task is only holding callback_mutex, then it has read-only
* access to cpusets.
*
- * The task_struct fields mems_allowed and mems_generation may only
- * be accessed in the context of that task, so require no locks.
+ * The task_struct fields mems_allowed may only be accessed in the context
+ * of that task, so require no locks.
*
* The cpuset_common_file_read() handlers only hold callback_mutex across
* small pieces of code, such as when reading out possibly multi-word
@@ -327,77 +300,6 @@ static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
}
-/**
- * cpuset_update_task_memory_state - update task memory placement
- *
- * If the current tasks cpusets mems_allowed changed behind our
- * backs, update current->mems_allowed, mems_generation and task NUMA
- * mempolicy to the new value.
- *
- * Task mempolicy is updated by rebinding it relative to the
- * current->cpuset if a task has its memory placement changed.
- * Do not call this routine if in_interrupt().
- *
- * Call without callback_mutex or task_lock() held. May be
- * called with or without cgroup_mutex held. Thanks in part to
- * 'the_top_cpuset_hack', the task's cpuset pointer will never
- * be NULL. This routine also might acquire callback_mutex during
- * call.
- *
- * Reading current->cpuset->mems_generation doesn't need task_lock
- * to guard the current->cpuset derefence, because it is guarded
- * from concurrent freeing of current->cpuset using RCU.
- *
- * The rcu_dereference() is technically probably not needed,
- * as I don't actually mind if I see a new cpuset pointer but
- * an old value of mems_generation. However this really only
- * matters on alpha systems using cpusets heavily. If I dropped
- * that rcu_dereference(), it would save them a memory barrier.
- * For all other arch's, rcu_dereference is a no-op anyway, and for
- * alpha systems not using cpusets, another planned optimization,
- * avoiding the rcu critical section for tasks in the root cpuset
- * which is statically allocated, so can't vanish, will make this
- * irrelevant. Better to use RCU as intended, than to engage in
- * some cute trick to save a memory barrier that is impossible to
- * test, for alpha systems using cpusets heavily, which might not
- * even exist.
- *
- * This routine is needed to update the per-task mems_allowed data,
- * within the tasks context, when it is trying to allocate memory
- * (in various mm/mempolicy.c routines) and notices that some other
- * task has been modifying its cpuset.
- */
-
-void cpuset_update_task_memory_state(void)
-{
- int my_cpusets_mem_gen;
- struct task_struct *tsk = current;
- struct cpuset *cs;
-
- rcu_read_lock();
- my_cpusets_mem_gen = task_cs(tsk)->mems_generation;
- rcu_read_unlock();
-
- if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
- mutex_lock(&callback_mutex);
- task_lock(tsk);
- cs = task_cs(tsk); /* Maybe changed when task not locked */
- guarantee_online_mems(cs, &tsk->mems_allowed);
- tsk->cpuset_mems_generation = cs->mems_generation;
- if (is_spread_page(cs))
- tsk->flags |= PF_SPREAD_PAGE;
- else
- tsk->flags &= ~PF_SPREAD_PAGE;
- if (is_spread_slab(cs))
- tsk->flags |= PF_SPREAD_SLAB;
- else
- tsk->flags &= ~PF_SPREAD_SLAB;
- task_unlock(tsk);
- mutex_unlock(&callback_mutex);
- mpol_rebind_task(tsk, &tsk->mems_allowed);
- }
-}
-
/*
* is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
*
@@ -990,14 +892,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
* other task, the task_struct mems_allowed that we are hacking
* is for our current task, which must allocate new pages for that
* migrating memory region.
- *
- * We call cpuset_update_task_memory_state() before hacking
- * our tasks mems_allowed, so that we are assured of being in
- * sync with our tasks cpuset, and in particular, callbacks to
- * cpuset_update_task_memory_state() from nested page allocations
- * won't see any mismatch of our cpuset and task mems_generation
- * values, so won't overwrite our hacked tasks mems_allowed
- * nodemask.
*/
static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
@@ -1005,8 +899,6 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
{
struct task_struct *tsk = current;
- cpuset_update_task_memory_state();
-
mutex_lock(&callback_mutex);
tsk->mems_allowed = *to;
mutex_unlock(&callback_mutex);
@@ -1076,6 +968,10 @@ static int update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem)
"Cpuset mempolicy rebind incomplete.\n");
break;
}
+ mutex_lock(&callback_mutex);
+ guarantee_online_mems(cs, &p->mems_allowed);
+ mutex_unlock(&callback_mutex);
+ mpol_rebind_task(p, &p->mems_allowed);
mm = get_task_mm(p);
if (!mm)
continue;
@@ -1118,10 +1014,9 @@ done:
/*
* Handle user request to change the 'mems' memory placement
* of a cpuset. Needs to validate the request, update the
- * cpusets mems_allowed and mems_generation, and for each
- * task in the cpuset, rebind any vma mempolicies and if
- * the cpuset is marked 'memory_migrate', migrate the tasks
- * pages to the new memory.
+ * cpusets mems_allowed, and for each task in the cpuset,
+ * rebind any vma mempolicies and if the cpuset is marked
+ * 'memory_migrate', migrate the tasks pages to the new memory.
*
* Call with cgroup_mutex held. May take callback_mutex during call.
* Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
@@ -1169,7 +1064,6 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
mutex_lock(&callback_mutex);
cs->mems_allowed = trialcs->mems_allowed;
- cs->mems_generation = cpuset_mems_generation++;
mutex_unlock(&callback_mutex);
retval = update_tasks_nodemask(cs, &oldmem);
@@ -1197,6 +1091,33 @@ static int update_relax_domain_level(struct cpuset *cs, s64 val)
return 0;
}
+static void cpuset_change_flag(struct task_struct *tsk,
+ struct cgroup_scanner *scan)
+{
+ struct cpuset *cs;
+
+ cs = task_cs(tsk);
+ if (is_spread_page(cs))
+ tsk->flags |= PF_SPREAD_PAGE;
+ else
+ tsk->flags &= ~PF_SPREAD_PAGE;
+ if (is_spread_slab(cs))
+ tsk->flags |= PF_SPREAD_SLAB;
+ else
+ tsk->flags &= ~PF_SPREAD_SLAB;
+}
+
+static void update_tasks_flags(struct cpuset *cs, struct ptr_heap *heap)
+{
+ struct cgroup_scanner scan;
+
+ scan.cg = cs->css.cgroup;
+ scan.test_task = NULL;
+ scan.process_task = cpuset_change_flag;
+ scan.heap = heap;
+ cgroup_scan_tasks(&scan);
+}
+
/*
* update_flag - read a 0 or a 1 in a file and update associated flag
* bit: the bit to update (see cpuset_flagbits_t)
@@ -1212,6 +1133,8 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
struct cpuset *trialcs;
int err;
int balance_flag_changed;
+ int spread_changed;
+ struct ptr_heap heap;
trialcs = alloc_trial_cpuset(cs);
if (!trialcs)
@@ -1226,9 +1149,16 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
if (err < 0)
goto out;
+ err = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
+ if (err)
+ goto out;
+
balance_flag_changed = (is_sched_load_balance(cs) !=
is_sched_load_balance(trialcs));
+ spread_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
+ || (is_spread_page(cs) != is_spread_page(trialcs)));
+
mutex_lock(&callback_mutex);
cs->flags = trialcs->flags;
mutex_unlock(&callback_mutex);
@@ -1236,6 +1166,10 @@ static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
async_rebuild_sched_domains();
+ if (spread_changed)
+ update_tasks_flags(cs, &heap);
+
+ heap_free(&heap);
out:
free_trial_cpuset(trialcs);
return err;
@@ -1374,15 +1308,29 @@ static void cpuset_attach(struct cgroup_subsys *ss,
if (cs == &top_cpuset) {
cpumask_copy(cpus_attach, cpu_possible_mask);
+ tsk->mems_allowed = node_possible_map;
} else {
mutex_lock(&callback_mutex);
guarantee_online_cpus(cs, cpus_attach);
+ guarantee_online_mems(cs,&tsk->mems_allowed);
mutex_unlock(&callback_mutex);
}
err = set_cpus_allowed_ptr(tsk, cpus_attach);
if (err)
return;
+ mutex_lock(&callback_mutex);
+ if (is_spread_page(cs))
+ tsk->flags |= PF_SPREAD_PAGE;
+ else
+ tsk->flags &= ~PF_SPREAD_PAGE;
+ if (is_spread_slab(cs))
+ tsk->flags |= PF_SPREAD_SLAB;
+ else
+ tsk->flags &= ~PF_SPREAD_SLAB;
+ mutex_unlock(&callback_mutex);
+ mpol_rebind_task(tsk, &tsk->mems_allowed);
+
from = oldcs->mems_allowed;
to = cs->mems_allowed;
mm = get_task_mm(tsk);
@@ -1444,11 +1392,9 @@ static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
break;
case FILE_SPREAD_PAGE:
retval = update_flag(CS_SPREAD_PAGE, cs, val);
- cs->mems_generation = cpuset_mems_generation++;
break;
case FILE_SPREAD_SLAB:
retval = update_flag(CS_SPREAD_SLAB, cs, val);
- cs->mems_generation = cpuset_mems_generation++;
break;
default:
retval = -EINVAL;
@@ -1787,8 +1733,6 @@ static struct cgroup_subsys_state *cpuset_create(
struct cpuset *parent;
if (!cont->parent) {
- /* This is early initialization for the top cgroup */
- top_cpuset.mems_generation = cpuset_mems_generation++;
return &top_cpuset.css;
}
parent = cgroup_cs(cont->parent);
@@ -1800,7 +1744,6 @@ static struct cgroup_subsys_state *cpuset_create(
return ERR_PTR(-ENOMEM);
}
- cpuset_update_task_memory_state();
cs->flags = 0;
if (is_spread_page(parent))
set_bit(CS_SPREAD_PAGE, &cs->flags);
@@ -1809,7 +1752,6 @@ static struct cgroup_subsys_state *cpuset_create(
set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
cpumask_clear(cs->cpus_allowed);
nodes_clear(cs->mems_allowed);
- cs->mems_generation = cpuset_mems_generation++;
fmeter_init(&cs->fmeter);
cs->relax_domain_level = -1;
@@ -1828,8 +1770,6 @@ static void cpuset_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
struct cpuset *cs = cgroup_cs(cont);
- cpuset_update_task_memory_state();
-
if (is_sched_load_balance(cs))
update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
@@ -1850,21 +1790,6 @@ struct cgroup_subsys cpuset_subsys = {
.early_init = 1,
};
-/*
- * cpuset_init_early - just enough so that the calls to
- * cpuset_update_task_memory_state() in early init code
- * are harmless.
- */
-
-int __init cpuset_init_early(void)
-{
- alloc_bootmem_cpumask_var(&top_cpuset.cpus_allowed);
-
- top_cpuset.mems_generation = cpuset_mems_generation++;
- return 0;
-}
-
-
/**
* cpuset_init - initialize cpusets at system boot
*
@@ -1875,11 +1800,12 @@ int __init cpuset_init(void)
{
int err = 0;
+ if (!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL))
+ BUG();
cpumask_setall(top_cpuset.cpus_allowed);
nodes_setall(top_cpuset.mems_allowed);
fmeter_init(&top_cpuset.fmeter);
- top_cpuset.mems_generation = cpuset_mems_generation++;
set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
top_cpuset.relax_domain_level = -1;
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 4fbc456..90469e6 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -242,6 +242,7 @@ int kthreadd(void *unused)
set_user_nice(tsk, KTHREAD_NICE_LEVEL);
set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
+ current->mems_allowed = node_possible_map;
current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
for (;;) {
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 3eb4a6f..5912b03 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -222,10 +222,6 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
policy->flags = flags;
if (nodes) {
- /*
- * cpuset related setup doesn't apply to local allocation
- */
- cpuset_update_task_memory_state();
if (flags & MPOL_F_RELATIVE_NODES)
mpol_relative_nodemask(&cpuset_context_nmask, nodes,
&cpuset_current_mems_allowed);
@@ -674,7 +670,6 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
struct vm_area_struct *vma = NULL;
struct mempolicy *pol = current->mempolicy;
- cpuset_update_task_memory_state();
if (flags &
~(unsigned long)(MPOL_F_NODE|MPOL_F_ADDR|MPOL_F_MEMS_ALLOWED))
return -EINVAL;
@@ -1545,8 +1540,6 @@ alloc_page_vma(gfp_t gfp, struct vm_area_struct *vma, unsigned long addr)
struct mempolicy *pol = get_vma_policy(current, vma, addr);
struct zonelist *zl;
- cpuset_update_task_memory_state();
-
if (unlikely(pol->mode == MPOL_INTERLEAVE)) {
unsigned nid;
@@ -1585,16 +1578,11 @@ alloc_page_vma(gfp_t gfp, struct vm_area_struct *vma, unsigned long addr)
* interrupt context and apply the current process NUMA policy.
* Returns NULL when no page can be allocated.
*
- * Don't call cpuset_update_task_memory_state() unless
- * 1) it's ok to take cpuset_sem (can WAIT), and
- * 2) allocating for current task (not interrupt).
*/
struct page *alloc_pages_current(gfp_t gfp, unsigned order)
{
struct mempolicy *pol = current->mempolicy;
- if ((gfp & __GFP_WAIT) && !in_interrupt())
- cpuset_update_task_memory_state();
if (!pol || in_interrupt() || (gfp & __GFP_THISNODE))
pol = &default_policy;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5675b30..503219c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1573,10 +1573,7 @@ nofail_alloc:
/* We now go into synchronous reclaim */
cpuset_memory_pressure_bump();
- /*
- * The task's cpuset might have expanded its set of allowable nodes
- */
- cpuset_update_task_memory_state();
+
p->flags |= PF_MEMALLOC;
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;
--
1.6.0.3
On Wednesday 21 January 2009 19:06:20 Miao Xie wrote:
> The task still allocated the page caches on old node after modifying its
> cpuset's mems when 'memory_spread_page' was set, it is caused by the old
> mem_allowed_list of the task, the current kernel doesn't updates it unless
> some function invokes cpuset_update_task_memory_state(), it is too late
> sometimes. We must update the mem_allowed_list of the tasks in time.
>
> Slab has the same problem.
>
> We fixes the bug by updating tasks' mem_allowed_list and spread flag after
> its cpuset's mems or spread flag is changed.
Thank you, this is a much better way to handle the problem, and keeps
those costly function calls out of fastpaths.
I don't know the cpuset code well enough to review it right now, but
the mm/ pieces thank you kindly for it :) Nice patch.
On Wed, Jan 21, 2009 at 12:06 AM, Miao Xie <[email protected]> wrote:
> The task still allocated the page caches on old node after modifying its
> cpuset's mems when 'memory_spread_page' was set, it is caused by the old
> mem_allowed_list of the task, the current kernel doesn't updates it unless some
> function invokes cpuset_update_task_memory_state(), it is too late sometimes.
Can you give a more concrete example of how the current code can break?
> We must update the mem_allowed_list of the tasks in time.
This is a fairly fundamental change to the way that mems_allowed is
handled - it dates back to fairly early in cpusets' history.
> - * The task_struct fields mems_allowed and mems_generation may only
> - * be accessed in the context of that task, so require no locks.
> + * The task_struct fields mems_allowed may only be accessed in the context
> + * of that task, so require no locks.
This comment is no longer true, since mems_allowed is now being
updated by other processes.
What's to stop a task reading current->mems_allowed and racing with an
update from update_tasks_nodemask() ? Or else, why can that not lead
to badness?
Paul
On Wed, 21 Jan 2009 16:06:20 +0800
Miao Xie <[email protected]> wrote:
> The task still allocated the page caches on old node after modifying its
> cpuset's mems when 'memory_spread_page' was set, it is caused by the old
> mem_allowed_list of the task, the current kernel doesn't updates it unless some
> function invokes cpuset_update_task_memory_state(), it is too late sometimes.
> We must update the mem_allowed_list of the tasks in time.
>
> Slab has the same problem.
>
> We fixes the bug by updating tasks' mem_allowed_list and spread flag after
> its cpuset's mems or spread flag is changed.
>
>
> ...
>
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -242,6 +242,7 @@ int kthreadd(void *unused)
> set_user_nice(tsk, KTHREAD_NICE_LEVEL);
> set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
>
> + current->mems_allowed = node_possible_map;
> current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
Why this change? kthreadd() is called from rest_init(), before anyone
has had a chance to alter ->mems_allowed?
I queued the patch pending your response to Paul's questions, thanks.
What exactly is breaking? You do a memory spread in a set of nodes
determined by the cpuset? Or how do you restrict the nodes that memory
spread is allowed to cycle through?