On thu, 26 Dec 2013 18:22:10 +0800, Gu Zheng wrote:
> 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>
Reviewed-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
Thanks
Miao
> ---
> 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);
>
>
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