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Date: Thu, 18 Dec 2014 00:08:55 +0900
From: Changman Lee <cm224.lee@...il.com>
To: Chao Yu <chao2.yu@...sung.com>
Cc: Jaegeuk Kim <jaegeuk@...nel.org>,
Changman Lee <cm224.lee@...sung.com>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: merge two uchar variable in struct
node_info to reduce memory cost
Hi Yu,
This patch is effective only in 32 bit machine. In case of 64 bit
machine, nat_entry will be aligned in 8 bytes due to pointer variable
(i.e. struct list_head). So it can't get any benefit to reduce memory
usage. In the case of node_info, however, it will be gain in terms of
memory usage.
Hence, I think it's not correct for commit log to describe this patch.
Thanks,
Reviewed-by: Changman Lee <cm224.lee@...sung.com>
2014-12-15 18:33 GMT+09:00 Chao Yu <chao2.yu@...sung.com>:
> This patch moves one member of struct nat_entry: _flag_ to struct node_info,
> so _version_ in struct node_info and _flag_ with unsigned char type will merge
> to one 32-bit space in register/memory. Then the size of nat_entry will reduce
> its size from 28 bytes to 24 bytes and slab memory using by f2fs will be
> reduced.
>
> changes from v1:
> o introduce inline copy_node_info() to copy valid data from node info suggested
> by Jaegeuk Kim, it can avoid bug.
>
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> ---
> fs/f2fs/node.c | 4 ++--
> fs/f2fs/node.h | 33 ++++++++++++++++++++++-----------
> 2 files changed, 24 insertions(+), 13 deletions(-)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index f83326c..5aa54a0 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -268,7 +268,7 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
> e = __lookup_nat_cache(nm_i, ni->nid);
> if (!e) {
> e = grab_nat_entry(nm_i, ni->nid);
> - e->ni = *ni;
> + copy_node_info(&e->ni, ni);
> f2fs_bug_on(sbi, ni->blk_addr == NEW_ADDR);
> } else if (new_blkaddr == NEW_ADDR) {
> /*
> @@ -276,7 +276,7 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
> * previous nat entry can be remained in nat cache.
> * So, reinitialize it with new information.
> */
> - e->ni = *ni;
> + copy_node_info(&e->ni, ni);
> f2fs_bug_on(sbi, ni->blk_addr != NULL_ADDR);
> }
>
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index d10b644..eb59167 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -29,6 +29,14 @@
> /* return value for read_node_page */
> #define LOCKED_PAGE 1
>
> +/* For flag in struct node_info */
> +enum {
> + IS_CHECKPOINTED, /* is it checkpointed before? */
> + HAS_FSYNCED_INODE, /* is the inode fsynced before? */
> + HAS_LAST_FSYNC, /* has the latest node fsync mark? */
> + IS_DIRTY, /* this nat entry is dirty? */
> +};
> +
> /*
> * For node information
> */
> @@ -37,18 +45,11 @@ struct node_info {
> nid_t ino; /* inode number of the node's owner */
> block_t blk_addr; /* block address of the node */
> unsigned char version; /* version of the node */
> -};
> -
> -enum {
> - IS_CHECKPOINTED, /* is it checkpointed before? */
> - HAS_FSYNCED_INODE, /* is the inode fsynced before? */
> - HAS_LAST_FSYNC, /* has the latest node fsync mark? */
> - IS_DIRTY, /* this nat entry is dirty? */
> + unsigned char flag; /* for node information bits */
> };
>
> struct nat_entry {
> struct list_head list; /* for clean or dirty nat list */
> - unsigned char flag; /* for node information bits */
> struct node_info ni; /* in-memory node information */
> };
>
> @@ -63,20 +64,30 @@ struct nat_entry {
>
> #define inc_node_version(version) (++version)
>
> +static inline void copy_node_info(struct node_info *dst,
> + struct node_info *src)
> +{
> + dst->nid = src->nid;
> + dst->ino = src->ino;
> + dst->blk_addr = src->blk_addr;
> + dst->version = src->version;
> + /* should not copy flag here */
> +}
> +
> static inline void set_nat_flag(struct nat_entry *ne,
> unsigned int type, bool set)
> {
> unsigned char mask = 0x01 << type;
> if (set)
> - ne->flag |= mask;
> + ne->ni.flag |= mask;
> else
> - ne->flag &= ~mask;
> + ne->ni.flag &= ~mask;
> }
>
> static inline bool get_nat_flag(struct nat_entry *ne, unsigned int type)
> {
> unsigned char mask = 0x01 << type;
> - return ne->flag & mask;
> + return ne->ni.flag & mask;
> }
>
> static inline void nat_reset_flag(struct nat_entry *ne)
> --
> 2.1.2
>
>
>
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