[PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Holden Karau]

From: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com

This is an attempt at improving fat_mirror_bhs in sync mode [namely it
writes all of the data for a backup block, and then blocks untill
finished]. The old behaviour would write & block in smaller chunks, so
this should be slightly faster. It also removes the fixme requesting
that it be fixed to behave this way :-)
Signed-off-by: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com
---
Sorry about the mangled patch, this time it really shouldn't be mangled :-)
Important note; I do not normally play with filesystems. This MAY eat
your file system, it has not eaten mine but that does not mean much at
all [although I don't think it will]. I'd greatly appreciate comments
& suggestions. In case the patch gets mangled [again] I've put it up at
http://www.holdenkarau.com/~holden/projects/fat/001_improve_fat_sync_performance.patch


And now for the actual patch:

--- a/fs/fat/fatent.c	2006-09-19 23:42:06.000000000 -0400
+++ b/fs/fat/fatent.c	2006-10-25 19:14:14.000000000 -0400
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2004, OGAWA Hirofumi
+ * Copyright (C) 2006, Holden Karau [Xandros] 
  * Released under GPL v2.
  */
 
@@ -343,34 +344,46 @@ int fat_ent_read(struct inode *inode, st
 	return ops->ent_get(fatent);
 }
 
-/* FIXME: We can write the blocks as more big chunk. */
 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
-			  int nr_bhs)
+			  int nr_bhs ) {
+  return fat_mirror_bhs_optw(sb , bhs , nr_bhs, 0);
+}
+
+static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
+			       int nr_bhs , int wait)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
-	struct buffer_head *c_bh;
+	struct buffer_head *c_bh[nr_bhs];
 	int err, n, copy;
 
+	/* Always wait if mounted -o sync */
+	if (sb->s_flags & MS_SYNCHRONOUS ) {
+	  wait = 1;
+	}
+
 	err = 0;
+	err = fat_sync_bhs_optw( bhs  , nr_bhs , wait);
+	if (err)
+	  goto error;
 	for (copy = 1; copy < sbi->fats; copy++) {
 		sector_t backup_fat = sbi->fat_length * copy;
-
 		for (n = 0; n < nr_bhs; n++) {
-			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
-			if (!c_bh) {
+	    c_bh[n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
+	    if (!c_bh[n]) {
 				err = -ENOMEM;
 				goto error;
 			}
-			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
-			set_buffer_uptodate(c_bh);
-			mark_buffer_dirty(c_bh);
-			if (sb->s_flags & MS_SYNCHRONOUS)
-				err = sync_dirty_buffer(c_bh);
-			brelse(c_bh);
+	    set_buffer_uptodate(c_bh[n]);
+	    mark_buffer_dirty(c_bh[n]);
+	    memcpy(c_bh[n]->b_data, bhs[n]->b_data, sb->s_blocksize);
+	  }
+	  err = fat_sync_bhs_optw( c_bh  , nr_bhs , wait );
+	  for (n = 0; n < nr_bhs; n++ ) {
+	    brelse(c_bh[n]);
+	  }
 			if (err)
 				goto error;
 		}
-	}
 error:
 	return err;
 }
@@ -383,12 +396,7 @@ int fat_ent_write(struct inode *inode, s
 	int err;
 
 	ops->ent_put(fatent, new);
-	if (wait) {
-		err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
-		if (err)
-			return err;
-	}
-	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
+	return fat_mirror_bhs_optw(sb, fatent->bhs, fatent->nr_bhs , wait);
 }
 
 static inline int fat_ent_next(struct msdos_sb_info *sbi,
@@ -505,9 +513,9 @@ out:
 	fatent_brelse(&fatent);
 	if (!err) {
 		if (inode_needs_sync(inode))
-			err = fat_sync_bhs(bhs, nr_bhs);
-		if (!err)
-			err = fat_mirror_bhs(sb, bhs, nr_bhs);
+		  err = fat_mirror_bhs_optw(sb , bhs, nr_bhs , 1);
+		else
+		  err = fat_mirror_bhs_optw(sb, bhs, nr_bhs , 0 );
 	}
 	for (i = 0; i < nr_bhs; i++)
 		brelse(bhs[i]);
@@ -549,11 +557,6 @@ int fat_free_clusters(struct inode *inod
 		}
 
 		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
-			if (sb->s_flags & MS_SYNCHRONOUS) {
-				err = fat_sync_bhs(bhs, nr_bhs);
-				if (err)
-					goto error;
-			}
 			err = fat_mirror_bhs(sb, bhs, nr_bhs);
 			if (err)
 				goto error;
@@ -564,11 +567,6 @@ int fat_free_clusters(struct inode *inod
 		fat_collect_bhs(bhs, &nr_bhs, &fatent);
 	} while (cluster != FAT_ENT_EOF);
 
-	if (sb->s_flags & MS_SYNCHRONOUS) {
-		err = fat_sync_bhs(bhs, nr_bhs);
-		if (err)
-			goto error;
-	}
 	err = fat_mirror_bhs(sb, bhs, nr_bhs);
 error:
 	fatent_brelse(&fatent);
--- a/fs/fat/misc.c	2006-09-19 23:42:06.000000000 -0400
+++ b/fs/fat/misc.c	2006-10-25 18:54:27.000000000 -0400
@@ -194,11 +194,17 @@ void fat_date_unix2dos(int unix_date, __
 
 EXPORT_SYMBOL_GPL(fat_date_unix2dos);
 
-int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
+
+int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs ) {
+  return fat_sync_bhs_optw(bhs , nr_bhs , 1);
+}
+
+int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs ,int wait)
 {
 	int i, err = 0;
 
 	ll_rw_block(SWRITE, nr_bhs, bhs);
+	if (wait) {
 	for (i = 0; i < nr_bhs; i++) {
 		wait_on_buffer(bhs[i]);
 		if (buffer_eopnotsupp(bhs[i])) {
@@ -207,6 +213,7 @@ int fat_sync_bhs(struct buffer_head **bh
 		} else if (!err && !buffer_uptodate(bhs[i]))
 			err = -EIO;
 	}
+	}
 	return err;
 }
 
--- a/include/linux/msdos_fs.h	2006-09-19 23:42:06.000000000 -0400
+++ b/include/linux/msdos_fs.h	2006-10-25 18:53:50.000000000 -0400
@@ -419,6 +419,7 @@ extern int fat_chain_add(struct inode *i
 extern int date_dos2unix(unsigned short time, unsigned short date);
 extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date);
 extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
+extern int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs, int wait);
 
 int fat_cache_init(void);
 void fat_cache_destroy(void);

Re: [PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Nick Piggin]

Holden Karau wrote:
> From: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com
> 
> This is an attempt at improving fat_mirror_bhs in sync mode [namely it
> writes all of the data for a backup block, and then blocks untill
> finished]. The old behaviour would write & block in smaller chunks, so
> this should be slightly faster. It also removes the fixme requesting
> that it be fixed to behave this way :-)
> Signed-off-by: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com

So how much is performance improved?

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

Re: [PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Jörn Engel]

I didn't pay too much attention, but found some low hanging fruits.

On Thu, 26 October 2006 07:59:42 -0400, Holden Karau wrote:
>  
> -/* FIXME: We can write the blocks as more big chunk. */
>  static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
> -			  int nr_bhs)
> +			  int nr_bhs ) {
> +  return fat_mirror_bhs_optw(sb , bhs , nr_bhs, 0);
> +}
> +
> +static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
> +			       int nr_bhs , int wait)

Does this compile without warnings?  Looks as if you should reverse
the order of the two functions.

>  {
>  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> -	struct buffer_head *c_bh;
> +	struct buffer_head *c_bh[nr_bhs];
>  	int err, n, copy;
>  
> +	/* Always wait if mounted -o sync */
> +	if (sb->s_flags & MS_SYNCHRONOUS ) {
> +	  wait = 1;
> +	}

Coding style.  Use a tab for indentation and don't use braces for
single-line conditional statements.

> +
>  	err = 0;
> +	err = fat_sync_bhs_optw( bhs  , nr_bhs , wait);

The err=0; is superfluous now, isn't it?

> +	if (err)
> +	  goto error;

Indentation.

Jörn

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while fantasy embraces the whole world.
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Re: [PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Holden Karau]

Based on some rather off-the cuff bench marking I've done I get around
a 5 to 10% performance improve over the stock 2.6.18.1 performance. As
the saying goes, there are lies, damn lies, and bench marks, so YMMV.

On 10/26/06, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Holden Karau wrote:
> > From: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com
> >
> > This is an attempt at improving fat_mirror_bhs in sync mode [namely it
> > writes all of the data for a backup block, and then blocks untill
> > finished]. The old behaviour would write & block in smaller chunks, so
> > this should be slightly faster. It also removes the fixme requesting
> > that it be fixed to behave this way :-)
> > Signed-off-by: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com
>
> So how much is performance improved?
>
> --
> SUSE Labs, Novell Inc.
> Send instant messages to your online friends http://au.messenger.yahoo.com
>
>


-- 
Cell: 613-276-1645

Re: [PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Holden Karau]

Hi Jörn,

Thanks for your time, I'll make those changes [along with a few other
things I noticed while benchmarking it]. Before I put together a
patch, does anyone else see any obvious stuff I should clean up?

Cheers,

Holden :-)

On 10/26/06, Jörn Engel <joern@wohnheim.fh-wedel.de> wrote:
> I didn't pay too much attention, but found some low hanging fruits.
>
> On Thu, 26 October 2006 07:59:42 -0400, Holden Karau wrote:
> >
> > -/* FIXME: We can write the blocks as more big chunk. */
> >  static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
> > -                       int nr_bhs)
> > +                       int nr_bhs ) {
> > +  return fat_mirror_bhs_optw(sb , bhs , nr_bhs, 0);
> > +}
> > +
> > +static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
> > +                            int nr_bhs , int wait)
>
> Does this compile without warnings?  Looks as if you should reverse
> the order of the two functions.
>
For some reason it compiles without warnings for me, but I'll switch the order.
> >  {
> >       struct msdos_sb_info *sbi = MSDOS_SB(sb);
> > -     struct buffer_head *c_bh;
> > +     struct buffer_head *c_bh[nr_bhs];
> >       int err, n, copy;
> >
> > +     /* Always wait if mounted -o sync */
> > +     if (sb->s_flags & MS_SYNCHRONOUS ) {
> > +       wait = 1;
> > +     }
>
> Coding style.  Use a tab for indentation and don't use braces for
> single-line conditional statements.
>
Sorry about that. A lot of the places where I used braces are because
I had some debugging output in there while I was hacking on it. I'll
change it.
> > +
> >       err = 0;
> > +     err = fat_sync_bhs_optw( bhs  , nr_bhs , wait);
>
> The err=0; is superfluous now, isn't it?
>
.... no comment :-)
> > +     if (err)
> > +       goto error;
>
> Indentation.
>
oops :-) I'll fix that.
> Jörn
>
> --
> Fantasy is more important than knowledge. Knowledge is limited,
> while fantasy embraces the whole world.
> -- Albert Einstein
>


-- 
Cell: 613-276-1645

Re: [PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]

[Josef Sipek]

Some of these may overlap with what others suggested.

On Thu, Oct 26, 2006 at 07:59:42AM -0400, Holden Karau wrote:
...
> --- a/fs/fat/fatent.c	2006-09-19 23:42:06.000000000 -0400
> +++ b/fs/fat/fatent.c	2006-10-25 19:14:14.000000000 -0400
...
> -/* FIXME: We can write the blocks as more big chunk. */
>  static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
> -			  int nr_bhs)
> +			  int nr_bhs ) {
> +  return fat_mirror_bhs_optw(sb , bhs , nr_bhs, 0);
> +}

Coding style... (brackets and indentation)

> +static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
> +			       int nr_bhs , int wait)
>  {
>  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> -	struct buffer_head *c_bh;
> +	struct buffer_head *c_bh[nr_bhs];
>  	int err, n, copy;
>  
> +	/* Always wait if mounted -o sync */
> +	if (sb->s_flags & MS_SYNCHRONOUS ) {
> +	  wait = 1;
> +	}

Ditto (indentation).

>  	err = 0;
> +	err = fat_sync_bhs_optw( bhs  , nr_bhs , wait);
> +	if (err)
> +	  goto error;
>  	for (copy = 1; copy < sbi->fats; copy++) {
>  		sector_t backup_fat = sbi->fat_length * copy;
> -
>  		for (n = 0; n < nr_bhs; n++) {
> -			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
> -			if (!c_bh) {
> +	    c_bh[n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
> +	    if (!c_bh[n]) {
>  				err = -ENOMEM;
>  				goto error;
>  			}
> -			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
> -			set_buffer_uptodate(c_bh);
> -			mark_buffer_dirty(c_bh);
> -			if (sb->s_flags & MS_SYNCHRONOUS)
> -				err = sync_dirty_buffer(c_bh);
> -			brelse(c_bh);
> +	    set_buffer_uptodate(c_bh[n]);
> +	    mark_buffer_dirty(c_bh[n]);
> +	    memcpy(c_bh[n]->b_data, bhs[n]->b_data, sb->s_blocksize);
> +	  }
> +	  err = fat_sync_bhs_optw( c_bh  , nr_bhs , wait );
> +	  for (n = 0; n < nr_bhs; n++ ) {
> +	    brelse(c_bh[n]);
> +	  }
>  			if (err)
>  				goto error;
>  		}
> -	}
>  error:
>  	return err;
>  }

Ditto.

> @@ -505,9 +513,9 @@ out:
>  	fatent_brelse(&fatent);
>  	if (!err) {
>  		if (inode_needs_sync(inode))
> -			err = fat_sync_bhs(bhs, nr_bhs);
> -		if (!err)
> -			err = fat_mirror_bhs(sb, bhs, nr_bhs);
> +		  err = fat_mirror_bhs_optw(sb , bhs, nr_bhs , 1);
> +		else
> +		  err = fat_mirror_bhs_optw(sb, bhs, nr_bhs , 0 );

Ditto.

> --- a/fs/fat/misc.c	2006-09-19 23:42:06.000000000 -0400
> +++ b/fs/fat/misc.c	2006-10-25 18:54:27.000000000 -0400
> @@ -194,11 +194,17 @@ void fat_date_unix2dos(int unix_date, __
>  
>  EXPORT_SYMBOL_GPL(fat_date_unix2dos);
>  
> -int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
> +
> +int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs ) {
> +  return fat_sync_bhs_optw(bhs , nr_bhs , 1);
> +}

Indentation & bracket placement.

> +int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs ,int wait)
>  {
>  	int i, err = 0;
>  
>  	ll_rw_block(SWRITE, nr_bhs, bhs);
> +	if (wait) {
>  	for (i = 0; i < nr_bhs; i++) {
>  		wait_on_buffer(bhs[i]);
>  		if (buffer_eopnotsupp(bhs[i])) {
> @@ -207,6 +213,7 @@ int fat_sync_bhs(struct buffer_head **bh
>  		} else if (!err && !buffer_uptodate(bhs[i]))
>  			err = -EIO;
>  	}
> +	}
 
Indentation.
 
Josef "Jeff" Sipek.

-- 
Mankind invented the atomic bomb, but no mouse would ever construct a
mousetrap.
		- Albert Einstein