[PATCH v4] EXT4: optimizing group search for inode allocation

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you are right flex groups cannot be completely empty as some 
blocks are used for inode table and allocation bitmaps. I
missed that point. I have corrected that.Also I have tested
and validated this patch by putting  some traces it works!
Here are corresponding logs:
commands:
=========
mkfs.ext4 -g 10000 -G 2 /dev/sdc
mount -t ext4  /dev/sdc /mnt/test_ext4/
cd /mnt/test_ext4
mkdir 1
cd 1

logs:
=====
Jan  7 03:36:45 root kernel: [   64.792939] max_usable_blocks_per_flex_group     =  [19692]
Jan  7 03:36:45 root kernel: [   64.792939] stats.free_clusters                  =  [19264]
Jan  7 03:36:45 root kernel: [   64.792939] Inodes_per_flex_group                =  [4864]
Jan  7 03:36:45 root kernel: [   64.792939] stats.free_inodes                    =  [4853]
Jan  7 03:36:45 root kernel: [   64.792950] max_usable_blocks_per_flex_group     =  [19692]
Jan  7 03:36:45 root kernel: [   64.792950] stats.free_clusters                  =  [19481]
Jan  7 03:36:45 root kernel: [   64.792950] Inodes_per_flex_group                =  [4864]
Jan  7 03:36:45 root kernel: [   64.792950] stats.free_inodes                    =  [4864]
Jan  7 03:36:45 root kernel: [   64.792958] max_usable_blocks_per_flex_group     =  [19692]
Jan  7 03:36:45 root kernel: [   64.792958] stats.free_clusters                  =  [19481]
Jan  7 03:36:45 root kernel: [   64.792958] Inodes_per_flex_group                =  [4864]
Jan  7 03:36:45 root kernel: [   64.792958] stats.free_inodes                    =  [4864]
Jan  7 03:36:45 root kernel: [   64.792965] max_usable_blocks_per_flex_group     =  [19692]
Jan  7 03:36:45 root kernel: [   64.792965] stats.free_clusters                  =  [19481]
Jan  7 03:36:45 root kernel: [   64.792965] Inodes_per_flex_group                =  [4864]
Jan  7 03:36:45 root kernel: [   64.792965] stats.free_inodes                    =  [4864]
Jan  7 03:36:45 root kernel: [   64.792972] max_usable_blocks_per_flex_group     =  [19692]
Jan  7 03:36:45 root kernel: [   64.792972] stats.free_clusters                  =  [19481]
Jan  7 03:36:45 root kernel: [   64.792972] Inodes_per_flex_group                =  [4864]
Jan  7 03:36:45 root kernel: [   64.792972] stats.free_inodes                    =  [4864]
Jan  7 03:36:45 root kernel: [   64.792979] max_usable_blocks_per_flex_group     =  [19692]<<<<<<<<<<<
Jan  7 03:36:45 root kernel: [   64.792979] stats.free_clusters                  =  [19692]<<<<<<<<<<<
Jan  7 03:36:45 root kernel: [   64.792979] Inodes_per_flex_group                =  [4864]<<<<<<<<<<<<
Jan  7 03:36:45 root kernel: [   64.792979] stats.free_inodes                    =  [4864]<<<<<<<<<<<<
Jan  7 03:36:45 root kernel: [   64.792985] found_flex_bg >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>condition satisfied 


[Patch v4]:
==========
From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
Date: Thu, 7 Jan 2016 05:12:20 +0530
Subject: [PATCH] ext4: optimizing group serch for inode allocation

Added a check at the start of group search loop to
avoid looping unecessarily in case of empty group.
This also allow group search to jump directly to
"found_flex_bg" with "stats" and "group" already set,
so there is no need to go through the extra steps of
setting "best_desc" , "best_group" and then break
out of the loop just to set "stats" and "group" again.

Signed-off-by: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
---
 fs/ext4/ext4.h   |    2 ++
 fs/ext4/ialloc.c |   21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index cc7ca4e..fc48f9a 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -326,6 +326,8 @@ struct flex_groups {
 #define        EXT4_MAX_DESC_SIZE              EXT4_MIN_BLOCK_SIZE
 #define EXT4_DESC_SIZE(s)              (EXT4_SB(s)->s_desc_size)
 #ifdef __KERNEL__
+# define EXT4_INODE_TABLE_BLOCKS_PER_GROUP(s)  (EXT4_SB(s)->s_itb_per_group)
+# define EXT4_BLOCKS_PER_CLUSTER(s)    (EXT4_SB(s)->s_cluster_ratio)
 # define EXT4_BLOCKS_PER_GROUP(s)      (EXT4_SB(s)->s_blocks_per_group)
 # define EXT4_CLUSTERS_PER_GROUP(s)    (EXT4_SB(s)->s_clusters_per_group)
 # define EXT4_DESC_PER_BLOCK(s)                (EXT4_SB(s)->s_desc_per_block)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 1b8024d..dc66ad8 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -463,7 +463,6 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
                        sbi->s_log_groups_per_flex;
                parent_group >>= sbi->s_log_groups_per_flex;
        }
-
        freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
        avefreei = freei / ngroups;
        freeb = EXT4_C2B(sbi,
@@ -477,7 +476,20 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
             (ext4_test_inode_flag(parent, EXT4_INODE_TOPDIR)))) {
                int best_ndir = inodes_per_group;
                int ret = -1;
-
+               /* blocks used for inode table and allocation bitmaps */
+               unsigned int max_usable_blocks_per_flex_group;
+               unsigned int blocks_per_group = EXT4_BLOCKS_PER_GROUP(sb);
+               unsigned int inode_table_blocks_per_group = \
+                               EXT4_INODE_TABLE_BLOCKS_PER_GROUP(sb);
+               /* Number of blocks per cluster */
+               unsigned int cluster_ratio = EXT4_BLOCKS_PER_CLUSTER(sb);
+               unsigned int inodes_per_flex_group = inodes_per_group * \
+                                                       flex_size;
+               max_usable_blocks_per_flex_group = \
+                                       ((blocks_per_group*flex_size) - \
+                                       (inode_table_blocks_per_group * \
+                                       flex_size + 2 * flex_size)) / \
+                                       cluster_ratio;
                if (qstr) {
                        hinfo.hash_version = DX_HASH_HALF_MD4;
                        hinfo.seed = sbi->s_hash_seed;
@@ -489,6 +501,11 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
                for (i = 0; i < ngroups; i++) {
                        g = (parent_group + i) % ngroups;
                        get_orlov_stats(sb, g, flex_size, &stats);
+                       /* can't get better group than empty group */
+                       if (max_usable_blocks_per_flex_group == \
+                               stats.free_clusters && \
+                               inodes_per_flex_group == stats.free_inodes)
+                                       goto found_flex_bg;
                        if (!stats.free_inodes)
                                continue;
                        if (stats.used_dirs >= best_ndir)
--
1.7.1

Regards,
Lokesh

On Sun, Jan 03, 2016 at 11:34:51AM -0700, Andreas Dilger wrote:
> On Dec 26, 2015, at 01:41, Lokesh Jaliminche <lokesh.jaliminche@xxxxxxxxx> wrote:
> > 
> > 
> > From 5199982d29ff291b181c25af63a22d6f2d6d3f7b Mon Sep 17 00:00:00 2001
> > From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
> > Date: Sat, 26 Dec 2015 13:19:36 +0530
> > Subject: [PATCH v3] ext4: optimizing group search for inode allocation
> > 
> > Added a check at the start of group search loop to
> > avoid looping unecessarily in case of empty group.
> > This also allow group search to jump directly to
> > "found_flex_bg" with "stats" and "group" already set,
> > so there is no need to go through the extra steps of
> > setting "best_desc" and "best_group" and then break
> > out of the loop just to set "stats" and "group" again.
> > 
> > Signed-off-by: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
> > ---
> > fs/ext4/ialloc.c |   12 ++++++++++--
> > 1 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> > index 1b8024d..16f94db 100644
> > --- a/fs/ext4/ialloc.c
> > +++ b/fs/ext4/ialloc.c
> > @@ -473,10 +473,14 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
> >        ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);
> > 
> >        if (S_ISDIR(mode) &&
> > -           ((parent == d_inode(sb->s_root)) ||
> > -            (ext4_test_inode_flag(parent, EXT4_INODE_TOPDIR)))) {
> > +               ((parent == d_inode(sb->s_root)) ||
> > +               (ext4_test_inode_flag(parent, EXT4_INODE_TOPDIR)))) {
> 
> I don't understand why you are changing the indentation here?
> 
> > +               unsigned int inodes_per_flex_group;
> > +               unsigned long int clusters_per_flex_group;
> >                int best_ndir = inodes_per_group;
> >                int ret = -1;
> > +               inodes_per_flex_group = inodes_per_group * flex_size;
> > +               clusters_per_flex_group = sbi->s_clusters_per_group * flex_size;
> 
> Have you actually tested if this code works?  When I was looking at this
> code I was accidentally looking at the ext2 version, which only deals with
> individual groups, and not flex groups.  I don't think that a flex group
> can actually be completely empty, since it will always contain at least
> an inode table and some bitmaps. 
> 
> This calculation needs to take this into account or it will just be
> overhead and not an optimization. Something like:
> 
>                 /* account for inode table and allocation bitmaps */
>                 clusters_per_flex_group = sbi->s_clusters_per_group * flex_size -
>                         ((inodes_per_flex_group * EXT4_INODE_SIZE(sb) +
>                           (flex_size << sb->s_blocksize_bits) * 2 ) >>
>                         EXT4_SB(sb)->s_cluster_bits;
> 
> It would be worthwhile to print this out and verify that there are actually
> groups with this many free blocks in a newly formatted filesystem.
> 
> Cheers, Andreas
> 
> >                if (qstr) {
> >                        hinfo.hash_version = DX_HASH_HALF_MD4;
> > @@ -489,6 +493,10 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
> >                for (i = 0; i < ngroups; i++) {
> >                        g = (parent_group + i) % ngroups;
> >                        get_orlov_stats(sb, g, flex_size, &stats);
> > +                       /* the group can't get any better than empty */
> > +                       if (inodes_per_flex_group == stats.free_inodes &&
> > +                               clusters_per_flex_group == stats.free_clusters)
> > +                               goto found_flex_bg;
> >                        if (!stats.free_inodes)
> >                                continue;
> >                        if (stats.used_dirs >= best_ndir)
> > -- 
> > 1.7.1
> > 
> > 
> >> On Mon, Dec 21, 2015 at 10:27:37AM -0700, Andreas Dilger wrote:
> >>> On Dec 18, 2015, at 4:32 PM, lokesh jaliminche <lokesh.jaliminche@xxxxxxxxx> wrote:
> >>> 
> >>> From 9e09fef78b2fa552c883bf8124af873abfde0805 Mon Sep 17 00:00:00 2001
> >>> From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxxxx>
> >> 
> >> In the patch summary there is a typo - s/serch/search/
> >> 
> >> Also, it appears your email client has mangled the whitespace in the
> >> patch.  Please use "git send-email" to send your patch to the list:
> >> 
> >>  git send-email --to tytso@xxxxxxx --cc linux-ext4@xxxxxxxxxxxxxxx HEAD~1
> >> 
> >> so that it arrives intact.  You probably need to set it up in ~/.gitconfig:
> >> 
> >> [sendemail]
> >>        confirm = compose
> >>        smtpdomain = {your client hostname}
> >>        smtpserver = {your SMTP server hostname}
> >> 
> >> Cheers, Andreas
> >> 
> >>> Added a check at the start of group search loop to
> >>> avoid looping unecessarily in case of empty group.
> >>> This also allow group search to jump directly to
> >>> "found_flex_bg" with "stats" and "group" already set,
> >>> so there is no need to go through the extra steps of
> >>> setting "best_desc" and "best_group" and then break
> >>> out of the loop just to set "stats" and "group" again.
> >>> 
> >>> Signed-off-by: Lokesh N Jaliminche <lokesh.jaliminche@xxxxxxxxx>
> >>> ---
> >>> fs/ext4/ialloc.c |    8 ++++++++
> >>> 1 files changed, 8 insertions(+), 0 deletions(-)
> >>> 
> >>> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> >>> index 1b8024d..588bf8e 100644
> >>> --- a/fs/ext4/ialloc.c
> >>> +++ b/fs/ext4/ialloc.c
> >>> @@ -446,6 +446,8 @@ static int find_group_orlov(struct super_block
> >>> *sb, struct inode *parent,
> >>> struct ext4_sb_info *sbi = EXT4_SB(sb);
> >>> ext4_group_t real_ngroups = ext4_get_groups_count(sb);
> >>> int inodes_per_group = EXT4_INODES_PER_GROUP(sb);
> >>> + unsigned int inodes_per_flex_group;
> >>> + long unsigned int blocks_per_clustre;
> >>> unsigned int freei, avefreei, grp_free;
> >>> ext4_fsblk_t freeb, avefreec;
> >>> unsigned int ndirs;
> >>> @@ -470,6 +472,8 @@ static int find_group_orlov(struct super_block
> >>> *sb, struct inode *parent,
> >>> percpu_counter_read_positive(&sbi->s_freeclusters_counter));
> >>> avefreec = freeb;
> >>> do_div(avefreec, ngroups);
> >>> + inodes_per_flex_group = inodes_per_group * flex_size;
> >>> + blocks_per_clustre = sbi->s_blocks_per_group * flex_size;
> >>> ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);
> >>> 
> >>> if (S_ISDIR(mode) &&
> >>> @@ -489,6 +493,10 @@ static int find_group_orlov(struct super_block
> >>> *sb, struct inode *parent,
> >>> for (i = 0; i < ngroups; i++) {
> >>> g = (parent_group + i) % ngroups;
> >>> get_orlov_stats(sb, g, flex_size, &stats);
> >>> + /* the group can't get any better than empty */
> >>> + if (inodes_per_flex_group == stats.free_inodes &&
> >>> + blocks_per_clustre == stats.free_clusters)
> >>> + goto found_flex_bg;
> >>> if (!stats.free_inodes)
> >>> continue;
> >>> if (stats.used_dirs >= best_ndir)
> >>> --
> >>> 1.7.1
> >>> <0001-EXT4-optimizing-group-serch-for-inode-allocation.patch>
> >> 
> >> 
> >> Cheers, Andreas
> > 
> > 
> > <0001-ext4-optimizing-group-serch-for-inode-allocation.patch>
>From 4734edcfb755096b1bcdd4153699ec907b072a35 Mon Sep 17 00:00:00 2001
From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
Date: Thu, 7 Jan 2016 05:12:20 +0530
Subject: [PATCH] ext4: optimizing group serch for inode allocation

Added a check at the start of group search loop to
avoid looping unecessarily in case of empty group.
This also allow group search to jump directly to
"found_flex_bg" with "stats" and "group" already set,
so there is no need to go through the extra steps of
setting "best_desc" , "best_group" and then break
out of the loop just to set "stats" and "group" again.

Signed-off-by: Lokesh Nagappa Jaliminche <lokesh.jaliminche@xxxxxxxxx>
---
 fs/ext4/ext4.h   |    2 ++
 fs/ext4/ialloc.c |   21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index cc7ca4e..fc48f9a 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -326,6 +326,8 @@ struct flex_groups {
 #define	EXT4_MAX_DESC_SIZE		EXT4_MIN_BLOCK_SIZE
 #define EXT4_DESC_SIZE(s)		(EXT4_SB(s)->s_desc_size)
 #ifdef __KERNEL__
+# define EXT4_INODE_TABLE_BLOCKS_PER_GROUP(s)	(EXT4_SB(s)->s_itb_per_group)
+# define EXT4_BLOCKS_PER_CLUSTER(s)	(EXT4_SB(s)->s_cluster_ratio)
 # define EXT4_BLOCKS_PER_GROUP(s)	(EXT4_SB(s)->s_blocks_per_group)
 # define EXT4_CLUSTERS_PER_GROUP(s)	(EXT4_SB(s)->s_clusters_per_group)
 # define EXT4_DESC_PER_BLOCK(s)		(EXT4_SB(s)->s_desc_per_block)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 1b8024d..dc66ad8 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -463,7 +463,6 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
 			sbi->s_log_groups_per_flex;
 		parent_group >>= sbi->s_log_groups_per_flex;
 	}
-
 	freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
 	avefreei = freei / ngroups;
 	freeb = EXT4_C2B(sbi,
@@ -477,7 +476,20 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
 	     (ext4_test_inode_flag(parent, EXT4_INODE_TOPDIR)))) {
 		int best_ndir = inodes_per_group;
 		int ret = -1;
-
+		/* blocks used for inode table and allocation bitmaps */
+		unsigned int max_usable_blocks_per_flex_group;
+		unsigned int blocks_per_group = EXT4_BLOCKS_PER_GROUP(sb);
+		unsigned int inode_table_blocks_per_group = \
+				EXT4_INODE_TABLE_BLOCKS_PER_GROUP(sb);
+		/* Number of blocks per cluster */
+		unsigned int cluster_ratio = EXT4_BLOCKS_PER_CLUSTER(sb);
+		unsigned int inodes_per_flex_group = inodes_per_group * \
+							flex_size;
+		max_usable_blocks_per_flex_group = \
+					((blocks_per_group*flex_size) - \
+					(inode_table_blocks_per_group * \
+					flex_size + 2 * flex_size)) / \
+					cluster_ratio;
 		if (qstr) {
 			hinfo.hash_version = DX_HASH_HALF_MD4;
 			hinfo.seed = sbi->s_hash_seed;
@@ -489,6 +501,11 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
 		for (i = 0; i < ngroups; i++) {
 			g = (parent_group + i) % ngroups;
 			get_orlov_stats(sb, g, flex_size, &stats);
+			/* can't get better group than empty group */
+			if (max_usable_blocks_per_flex_group == \
+				stats.free_clusters && \
+				inodes_per_flex_group == stats.free_inodes)
+					goto found_flex_bg;
 			if (!stats.free_inodes)
 				continue;
 			if (stats.used_dirs >= best_ndir)
-- 
1.7.1


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