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Date: Sun, 17 Jan 2016 04:20:11 +0530
From: Lokesh Jaliminche <lokesh.jaliminche@...il.com>
To: Andreas Dilger <adilger@...ger.ca>, Theodore Ts'o <tytso@....edu>
Cc: linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v5] EXT4: optimizing group search for inode allocation
From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@...il.com>
Date: Thu, 7 Jan 2016 05:12:20 +0530
Subject: [PATCH v5] 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@...il.com>
---
fs/ext4/ialloc.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 1b8024d..d2835cc 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -477,6 +477,12 @@ 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;
+ /* Maximum usable blocks per group as some blocks are used
+ * for inode tables and allocation bitmaps */
+ unsigned int max_blocks_per_flex =
+ ((sbi->s_blocks_per_group -
+ (sbi->s_itb_per_group + 2)) *
+ flex_size) >> sbi->s_cluster_bits;
if (qstr) {
hinfo.hash_version = DX_HASH_HALF_MD4;
@@ -489,6 +495,10 @@ 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);
+ /* can't get better group than empty group */
+ if (max_blocks_per_flex == stats.free_clusters &&
+ (inodes_per_group * flex_size) == stats.free_inodes)
+ goto found_flex_bg;
if (!stats.free_inodes)
continue;
if (stats.used_dirs >= best_ndir)
--.
1.7.1
On Mon, Jan 11, 2016 at 02:13:46PM -0700, Andreas Dilger wrote:
> On Jan 6, 2016, at 5:46 PM, Lokesh Jaliminche <lokesh.jaliminche@...il.com> wrote:
> >
> > 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!
>
> Good news. Thanks for updating the patch and testing it.
> More comments below.
>
> > 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@...il.com>
> > 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@...il.com>
> > ---
> > 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)
>
> I don't think there is much value to these macros. They aren't much
> shorter than the actual variable access, and they don't provide any
> improved clarity for the reader.
>
> I think they were introduced many years ago so that this header could
> be shared between the kernel and e2fsprogs, but that is no longer true
> so I don't think there is a need to add new ones.
>
> Ted, any opinion on this?
>
> > # 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;
>
> Not sure why this line is being deleted?
>
> > @@ -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;
>
> This could be shorter and still clear, like "max_blocks_per_flex".
>
> > + 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);
>
> There also isn't much value to making local variables that hold these
> same values again. It increases stack space for little benefit. They
> are only accessed once anyway.
>
> > + unsigned int inodes_per_flex_group = inodes_per_group * \
> > + flex_size;
> > + max_usable_blocks_per_flex_group = \
> > + ((blocks_per_group*flex_size) - \
>
> Spaces around that '*'.
>
> > + (inode_table_blocks_per_group * \
> > + flex_size + 2 * flex_size)) / \
>
> This is C and not a CPP macro, so no need for linefeed escapes.
>
> > + cluster_ratio;
>
> This should be ">> EXT4_SB(sb)->s_cluster_bits" to avoid the divide.
>
> > 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 && \
>
> No need for linefeed escapes.
>
> > + inodes_per_flex_group == stats.free_inodes)
>
> Align continued line after '(' from the "if (" line.
>
> > + goto found_flex_bg;
>
> This is indented too much. It will work properly when you fix the
> previous line.
>
> > 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@...il.com> wrote:
> >>>
> >>>
> >>> From 5199982d29ff291b181c25af63a22d6f2d6d3f7b Mon Sep 17 00:00:00 2001
> >>> From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@...il.com>
> >>> 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@...il.com>
> >>> ---
> >>> 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@...il.com> wrote:
> >>>>>
> >>>>> From 9e09fef78b2fa552c883bf8124af873abfde0805 Mon Sep 17 00:00:00 2001
> >>>>> From: Lokesh Nagappa Jaliminche <lokesh.jaliminche@...gate.com>
> >>>>
> >>>> 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@....edu --cc linux-ext4@...r.kernel.org 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@...il.com>
> >>>>> ---
> >>>>> 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>
> > <0001-ext4-optimizing-group-serch-for-inode-allocation.patch>
>
>
> Cheers, Andreas
>
>
>
>
>
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