Add a 'next_free' field into kioctx_table to store the next id that
may be free, in order to reduce the search region when we insert
kioctx into kioctx table.
When we take a free slot from kioctx_table, update 'next_free' to
the next slot. Also when we free one slot to kioctx_table, update 'next_free'
to the new free slot if it's smaller than 'next_free'. So that we can
ensure that the slots before 'next_free' are all used, and the search can start
from 'next_free' to reduce the search and improve the performance.
Signed-off-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx>
---
fs/aio.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 062a5f6..489fda6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -69,6 +69,7 @@ struct aio_ring {
struct kioctx_table {
struct rcu_head rcu;
unsigned nr;
+ unsigned next_free;
struct kioctx *table[];
};
@@ -548,11 +549,12 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
table = rcu_dereference(mm->ioctx_table);
while (1) {
- if (table)
- for (i = 0; i < table->nr; i++)
+ if (table && table->next_free < table->nr)
+ for (i = table->next_free; i < table->nr; i++)
if (!table->table[i]) {
ctx->id = i;
table->table[i] = ctx;
+ table->next_free = i + 1;
rcu_read_unlock();
spin_unlock(&mm->ioctx_lock);
@@ -579,8 +581,10 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
old = rcu_dereference(mm->ioctx_table);
if (!old) {
+ table->next_free = 0;
rcu_assign_pointer(mm->ioctx_table, table);
} else if (table->nr > old->nr) {
+ table->next_free = old->nr;
memcpy(table->table, old->table,
old->nr * sizeof(struct kioctx *));
@@ -716,6 +720,8 @@ static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
WARN_ON(ctx != table->table[ctx->id]);
table->table[ctx->id] = NULL;
+ if (ctx->id < table->next_free)
+ table->next_free = ctx->id;
rcu_read_unlock();
spin_unlock(&mm->ioctx_lock);
--
1.7.7
--
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