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authorMel Gorman <mgorman@suse.de>2014-04-03 14:47:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-03 16:20:58 -0700
commitd26914d11751b23ca2e8747725f2cae10c2f2c1b (patch)
tree020b606fb9223e29292f54922a11111239e3a3f4 /include/linux/cpuset.h
parent91ca9186484809c57303b33778d841cc28f696ed (diff)
downloadop-kernel-dev-d26914d11751b23ca2e8747725f2cae10c2f2c1b.zip
op-kernel-dev-d26914d11751b23ca2e8747725f2cae10c2f2c1b.tar.gz
mm: optimize put_mems_allowed() usage
Since put_mems_allowed() is strictly optional, its a seqcount retry, we don't need to evaluate the function if the allocation was in fact successful, saving a smp_rmb some loads and comparisons on some relative fast-paths. Since the naming, get/put_mems_allowed() does suggest a mandatory pairing, rename the interface, as suggested by Mel, to resemble the seqcount interface. This gives us: read_mems_allowed_begin() and read_mems_allowed_retry(), where it is important to note that the return value of the latter call is inverted from its previous incarnation. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/cpuset.h')
-rw-r--r--include/linux/cpuset.h27
1 files changed, 14 insertions, 13 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 3fe661f..b19d3dc 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -87,25 +87,26 @@ extern void rebuild_sched_domains(void);
extern void cpuset_print_task_mems_allowed(struct task_struct *p);
/*
- * get_mems_allowed is required when making decisions involving mems_allowed
- * such as during page allocation. mems_allowed can be updated in parallel
- * and depending on the new value an operation can fail potentially causing
- * process failure. A retry loop with get_mems_allowed and put_mems_allowed
- * prevents these artificial failures.
+ * read_mems_allowed_begin is required when making decisions involving
+ * mems_allowed such as during page allocation. mems_allowed can be updated in
+ * parallel and depending on the new value an operation can fail potentially
+ * causing process failure. A retry loop with read_mems_allowed_begin and
+ * read_mems_allowed_retry prevents these artificial failures.
*/
-static inline unsigned int get_mems_allowed(void)
+static inline unsigned int read_mems_allowed_begin(void)
{
return read_seqcount_begin(&current->mems_allowed_seq);
}
/*
- * If this returns false, the operation that took place after get_mems_allowed
- * may have failed. It is up to the caller to retry the operation if
+ * If this returns true, the operation that took place after
+ * read_mems_allowed_begin may have failed artificially due to a concurrent
+ * update of mems_allowed. It is up to the caller to retry the operation if
* appropriate.
*/
-static inline bool put_mems_allowed(unsigned int seq)
+static inline bool read_mems_allowed_retry(unsigned int seq)
{
- return !read_seqcount_retry(&current->mems_allowed_seq, seq);
+ return read_seqcount_retry(&current->mems_allowed_seq, seq);
}
static inline void set_mems_allowed(nodemask_t nodemask)
@@ -225,14 +226,14 @@ static inline void set_mems_allowed(nodemask_t nodemask)
{
}
-static inline unsigned int get_mems_allowed(void)
+static inline unsigned int read_mems_allowed_begin(void)
{
return 0;
}
-static inline bool put_mems_allowed(unsigned int seq)
+static inline bool read_mems_allowed_retry(unsigned int seq)
{
- return true;
+ return false;
}
#endif /* !CONFIG_CPUSETS */
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