mempolicy: restructure rebinding-mempolicy functions
Subsystems (2)
PATCH 1/2 mempolicy: restructure rebinding-mempolicy functions
In order to fix no node to alloc memory, when we want to update mempolicy and mems_allowed, we expand the set of nodes first (set all the newly nodes) and shrink the set of nodes lazily(clean disallowed nodes), But the mempolicy's rebind functions may breaks the expanding.
So we restructure the mempolicy's rebind functions and split the rebind work to two steps, just like the update of cpuset's mems:
The 1st step: expand the set of the mempolicy's nodes.
The 2nd step: shrink the set of the mempolicy's nodes.
It is used when there is no real lock to protect the mempolicy in the read-side. Otherwise we can do rebind work at once.
In order to implement it, we defined
enum mpol_rebind_step {
MPOL_REBIND_ONCE,
MPOL_REBIND_STEP1,
MPOL_REBIND_STEP2,
MPOL_REBIND_NSTEP,
};If the mempolicy needn't be updated by two steps, we can pass MPOL_REBIND_ONCE to the rebind functions. Or we can pass MPOL_REBIND_STEP1 to do the first step of the rebind work and pass MPOL_REBIND_STEP2 to do the second step work.
Besides that, it maybe long time between these two step and we have to release the lock that protects mempolicy and mems_allowed. If we hold the lock once again, we must check whether the current mempolicy is under the rebinding (the first step has been done) or not, because the task may alloc a new mempolicy when we don't hold the lock. So we defined the following flag to identify it.
#define MPOL_F_REBINDING (1 << 2)
The new functions will be used in the next patch.
--- include/linux/mempolicy.h | 15 ++++- kernel/cpuset.c | 4 +- mm/mempolicy.c | 124 ++++++++++++++++++++++++++++++++++++++------- 3 files changed, 119 insertions(+), 24 deletions(-)
include/linux/mempolicy.h +12 -3
@@ -23,6 +23,13 @@ enum { MPOL_MAX, /* always last member of enum */ }; +enum mpol_rebind_step { +MPOL_REBIND_ONCE ,/* do rebind work at once(not by two step) */ +MPOL_REBIND_STEP1 ,/* first step(set all the newly nodes) */ +MPOL_REBIND_STEP2 ,/* second step(clean all the disallowed nodes)*/ +MPOL_REBIND_NSTEP , +}; +/* Flags for set_mempolicy */ #define MPOL_F_STATIC_NODES (1 << 15)#define MPOL_F_RELATIVE_NODES (1 << 14)
@@ -51,6 +58,7 @@ enum {*/ #define MPOL_F_SHARED (1 << 0)/* identify shared policies */ #define MPOL_F_LOCAL (1 << 1)/* preferred local allocation */ +#define MPOL_F_REBINDING (1 << 2)/* identify policies in rebinding */ #ifdef __KERNEL__
@@ -193,8 +201,8 @@ struct mempolicy *mpol_shared_policy_lookup(struct shared_policy *sp,extern void numa_default_policy (void );extern void numa_policy_init (void ); -extern void mpol_rebind_task (struct task_struct *tsk, -const nodemask_t *new); +extern void mpol_rebind_task (struct task_struct *tsk,const nodemask_t *new, +enum mpol_rebind_step step);extern void mpol_rebind_mm (struct mm_struct *mm,nodemask_t *new);extern void mpol_fix_fork_child_flag (struct task_struct *p);
@@ -308,7 +316,8 @@ static inline void numa_default_policy(void) }static inline void mpol_rebind_task (struct task_struct *tsk, -const nodemask_t *new) +const nodemask_t *new, +enum mpol_rebind_step step) { }
kernel/cpuset.c +2 -2
@@ -953,8 +953,8 @@ static void cpuset_change_task_nodemask(struct task_struct *tsk, nodemask_t *newmems) {nodes_or (tsk->mems_allowed, tsk->mems_allowed, *newmems); -mpol_rebind_task (tsk, &tsk->mems_allowed); -mpol_rebind_task (tsk, newmems); +mpol_rebind_task (tsk, &tsk->mems_allowed,MPOL_REBIND_ONCE ); +mpol_rebind_task (tsk, newmems,MPOL_REBIND_ONCE ); tsk->mems_allowed = *newmems; }
mm/mempolicy.c +105 -19
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