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
