[f2fs-dev][PATCH v2] f2fs: merge two uchar variable in struct node_info to reduce memory cost

[f2fs-dev][PATCH v2] f2fs: merge two uchar variable in struct node_info to reduce memory cost

[Chao Yu]

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@samsung.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

Re: [f2fs-dev] [PATCH v2] f2fs: merge two uchar variable in struct node_info to reduce memory cost

[Changman Lee]

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@samsung.com>

2014-12-15 18:33 GMT+09:00 Chao Yu <chao2.yu@samsung.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@samsung.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
>
>
>
> ------------------------------------------------------------------------------
> Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server
> from Actuate! Instantly Supercharge Your Business Reports and Dashboards
> with Interactivity, Sharing, Native Excel Exports, App Integration & more
> Get technology previously reserved for billion-dollar corporations, FREE
> http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

Re: [PATCH v2] f2fs: merge two uchar variable in struct node_info to reduce memory cost

[Chao Yu]

Hi Changman,

> -----Original Message-----
> From: Changman Lee [mailto:cm224.lee@gmail.com]
> Sent: Wednesday, December 17, 2014 11:09 PM
> To: Chao Yu
> Cc: Jaegeuk Kim; Changman Lee; linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-f2fs-devel@lists.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 for your review! :)

AFFIK, in 64 bit machine, size of struct nat_entry is 40 bytes before this patch
apply, the reason is that our compiler will fill 3 bytes pads after flag as
nid's offset should align to type size of nid, and then fill 7 byte pads after
version as size of structure should align to 64 bits when the struct size is bigger
than 64 bits.
layout of struct nat_entry:
|-----8 bytes-----|
|list.next        |
|list.prev        |
|flag    |nid     |
|ino     |blk_addr|
|version          |
After we apply this patch, size of struct nat_entry will be reduced to 32 bytes.
Please correct me if I'm wrong.

Anyway, I agreed that commit log should be uptodate.

Thanks,
Yu

> Thanks,
> 
> Reviewed-by: Changman Lee <cm224.lee@samsung.com>
> 


------------------------------------------------------------------------------
Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server
from Actuate! Instantly Supercharge Your Business Reports and Dashboards
with Interactivity, Sharing, Native Excel Exports, App Integration & more
Get technology previously reserved for billion-dollar corporations, FREE
http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk

Re: [f2fs-dev] [PATCH v2] f2fs: merge two uchar variable in struct node_info to reduce memory cost

[Changman Lee]

On Thu, Dec 18, 2014 at 02:29:51PM +0800, Chao Yu wrote:
> Hi Changman,
> 
> > -----Original Message-----
> > From: Changman Lee [mailto:cm224.lee@gmail.com]
> > Sent: Wednesday, December 17, 2014 11:09 PM
> > To: Chao Yu
> > Cc: Jaegeuk Kim; Changman Lee; linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org;
> > linux-f2fs-devel@lists.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 for your review! :)
> 
> AFFIK, in 64 bit machine, size of struct nat_entry is 40 bytes before this patch
> apply, the reason is that our compiler will fill 3 bytes pads after flag as
> nid's offset should align to type size of nid, and then fill 7 byte pads after
> version as size of structure should align to 64 bits when the struct size is bigger
> than 64 bits.
> layout of struct nat_entry:
> |-----8 bytes-----|
> |list.next        |
> |list.prev        |
> |flag    |nid     |
> |ino     |blk_addr|
> |version          |
> After we apply this patch, size of struct nat_entry will be reduced to 32 bytes.
> Please correct me if I'm wrong.

Hi,

Sorry, you're right.
I miscalculated.

Thanks,

> 
> Anyway, I agreed that commit log should be uptodate.
> 
> Thanks,
> Yu
> 
> > Thanks,
> > 
> > Reviewed-by: Changman Lee <cm224.lee@samsung.com>
> >