On 11/27/2012 03:14 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Now that we have an LRU list API, we can start to enhance the
> implementation. This splits the single LRU list into per-node lists
> and locks to enhance scalability. Items are placed on lists
> according to the node the memory belongs to. To make scanning the
> lists efficient, also track whether the per-node lists have entries
> in them in a active nodemask.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> include/linux/list_lru.h | 14 ++--
> lib/list_lru.c | 160 +++++++++++++++++++++++++++++++++++-----------
> 2 files changed, 129 insertions(+), 45 deletions(-)
>
> diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> index 3423949..b0e3ba2 100644
> --- a/include/linux/list_lru.h
> +++ b/include/linux/list_lru.h
> @@ -8,21 +8,23 @@
> #define _LRU_LIST_H 0
>
> #include <linux/list.h>
> +#include <linux/nodemask.h>
>
> -struct list_lru {
> +struct list_lru_node {
> spinlock_t lock;
> struct list_head list;
> long nr_items;
> +} ____cacheline_aligned_in_smp;
> +
> +struct list_lru {
> + struct list_lru_node node[MAX_NUMNODES];
> + nodemask_t active_nodes;
> };
>
MAX_NUMNODES will default to 1 << 9, if I'm not mistaken. Your
list_lru_node seems to be around 32 bytes on 64-bit systems (128 with
debug). So we're talking about 16k per lru.
The superblocks only, are present by the dozens even in a small system,
and I believe the whole goal of this API is to get more users to switch
to it. This can easily use up a respectable bunch of megs.
Isn't it a bit too much ?
I am wondering if we can't do better in here and at least allocate+grow
according to the actual number of nodes.
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