| Message ID | 1223525160-9887-30-git-send-email-tytso@mit.edu |
|---|---|
| State | Accepted, archived |
| Headers | show |
On Thu, Oct 09, 2008 at 12:05:47AM -0400, Theodore Ts'o wrote: > With modern hard drives, reading 64k takes roughly the same time as > reading a 4k block. So request readahead for adjacent inode table > blocks to reduce the time it takes when iterating over directories > (especially when doing this in htree sort order) in a cold cache case. > With this patch, the time it takes to run "git status" on a kernel > tree after flushing the caches via "echo 3 > /proc/sys/vm/drop_caches" > is reduced by 21%. > > Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> > --- > fs/ext4/ext4.h | 2 + > fs/ext4/ext4_sb.h | 1 + > fs/ext4/inode.c | 134 +++++++++++++++++++++++++--------------------------- > fs/ext4/super.c | 27 ++++++++++- > 4 files changed, 92 insertions(+), 72 deletions(-) Need documentation for the new mount option and the /proc tunable. > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index 163c445..922d187 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -790,6 +790,8 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) > #define EXT4_DEF_RESUID 0 > #define EXT4_DEF_RESGID 0 > > +#define EXT4_DEF_INODE_READAHEAD_BLKS 32 > + > /* > * Default mount options > */ > diff --git a/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h > index f92af01..94e0757 100644 > --- a/fs/ext4/ext4_sb.h > +++ b/fs/ext4/ext4_sb.h > @@ -52,6 +52,7 @@ struct ext4_sb_info { > int s_desc_per_block_bits; > int s_inode_size; > int s_first_ino; > + unsigned int s_inode_readahead_blks; > spinlock_t s_next_gen_lock; > u32 s_next_generation; > u32 s_hash_seed[4]; > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 22fcbb6..ef4ca3d 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3833,41 +3833,6 @@ out_stop: > ext4_journal_stop(handle); > } > > -static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb, > - unsigned long ino, struct ext4_iloc *iloc) > -{ > - ext4_group_t block_group; > - unsigned long offset; > - ext4_fsblk_t block; > - struct ext4_group_desc *gdp; > - > - if (!ext4_valid_inum(sb, ino)) { > - /* > - * This error is already checked for in namei.c unless we are > - * looking at an NFS filehandle, in which case no error > - * report is needed > - */ > - return 0; > - } > - > - block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb); > - gdp = ext4_get_group_desc(sb, block_group, NULL); > - if (!gdp) > - return 0; > - > - /* > - * Figure out the offset within the block group inode table > - */ > - offset = ((ino - 1) % EXT4_INODES_PER_GROUP(sb)) * > - EXT4_INODE_SIZE(sb); > - block = ext4_inode_table(sb, gdp) + > - (offset >> EXT4_BLOCK_SIZE_BITS(sb)); > - > - iloc->block_group = block_group; > - iloc->offset = offset & (EXT4_BLOCK_SIZE(sb) - 1); > - return block; > -} > - > /* > * ext4_get_inode_loc returns with an extra refcount against the inode's > * underlying buffer_head on success. If 'in_mem' is true, we have all > @@ -3877,19 +3842,35 @@ static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb, > static int __ext4_get_inode_loc(struct inode *inode, > struct ext4_iloc *iloc, int in_mem) > { > - ext4_fsblk_t block; > - struct buffer_head *bh; > + struct ext4_group_desc *gdp; > + struct buffer_head *bh; > + struct super_block *sb = inode->i_sb; > + ext4_fsblk_t block; > + int inodes_per_block, inode_offset; > + > + iloc->bh = 0; > + if (!ext4_valid_inum(sb, inode->i_ino)) > + return -EIO; > > - block = ext4_get_inode_block(inode->i_sb, inode->i_ino, iloc); > - if (!block) > + iloc->block_group = (inode->i_ino - 1) / EXT4_INODES_PER_GROUP(sb); > + gdp = ext4_get_group_desc(sb, iloc->block_group, NULL); > + if (!gdp) > return -EIO; > > - bh = sb_getblk(inode->i_sb, block); > + /* > + * Figure out the offset within the block group inode table > + */ > + inodes_per_block = (EXT4_BLOCK_SIZE(sb) / EXT4_INODE_SIZE(sb)); > + inode_offset = ((inode->i_ino - 1) % > + EXT4_INODES_PER_GROUP(sb)); > + block = ext4_inode_table(sb, gdp) + (inode_offset / inodes_per_block); > + iloc->offset = (inode_offset % inodes_per_block) * EXT4_INODE_SIZE(sb); > + > + bh = sb_getblk(sb, block); > if (!bh) { > - ext4_error (inode->i_sb, "ext4_get_inode_loc", > - "unable to read inode block - " > - "inode=%lu, block=%llu", > - inode->i_ino, block); > + ext4_error(sb, "ext4_get_inode_loc", "unable to read " > + "inode block - inode=%lu, block=%llu", > + inode->i_ino, block); > return -EIO; > } > if (!buffer_uptodate(bh)) { > @@ -3917,28 +3898,12 @@ static int __ext4_get_inode_loc(struct inode *inode, > */ > if (in_mem) { > struct buffer_head *bitmap_bh; > - struct ext4_group_desc *desc; > - int inodes_per_buffer; > - int inode_offset, i; > - ext4_group_t block_group; > - int start; > - > - block_group = (inode->i_ino - 1) / > - EXT4_INODES_PER_GROUP(inode->i_sb); > - inodes_per_buffer = bh->b_size / > - EXT4_INODE_SIZE(inode->i_sb); > - inode_offset = ((inode->i_ino - 1) % > - EXT4_INODES_PER_GROUP(inode->i_sb)); > - start = inode_offset & ~(inodes_per_buffer - 1); > + int i, start; > > - /* Is the inode bitmap in cache? */ > - desc = ext4_get_group_desc(inode->i_sb, > - block_group, NULL); > - if (!desc) > - goto make_io; > + start = inode_offset & ~(inodes_per_block - 1); > > - bitmap_bh = sb_getblk(inode->i_sb, > - ext4_inode_bitmap(inode->i_sb, desc)); > + /* Is the inode bitmap in cache? */ > + bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp)); > if (!bitmap_bh) > goto make_io; > > @@ -3951,14 +3916,14 @@ static int __ext4_get_inode_loc(struct inode *inode, > brelse(bitmap_bh); > goto make_io; > } > - for (i = start; i < start + inodes_per_buffer; i++) { > + for (i = start; i < start + inodes_per_block; i++) { > if (i == inode_offset) > continue; > if (ext4_test_bit(i, bitmap_bh->b_data)) > break; > } > brelse(bitmap_bh); > - if (i == start + inodes_per_buffer) { > + if (i == start + inodes_per_block) { > /* all other inodes are free, so skip I/O */ > memset(bh->b_data, 0, bh->b_size); > set_buffer_uptodate(bh); > @@ -3969,6 +3934,36 @@ static int __ext4_get_inode_loc(struct inode *inode, > > make_io: > /* > + * If we need to do any I/O, try to pre-readahead extra > + * blocks from the inode table. > + */ > + if (EXT4_SB(sb)->s_inode_readahead_blks) { > + ext4_fsblk_t b, end, table; > + unsigned num; > + > + table = ext4_inode_table(sb, gdp); > + /* Make sure s_inode_readahead_blks is a power of 2 */ > + while (EXT4_SB(sb)->s_inode_readahead_blks & > + (EXT4_SB(sb)->s_inode_readahead_blks-1)) > + EXT4_SB(sb)->s_inode_readahead_blks = > + (EXT4_SB(sb)->s_inode_readahead_blks & > + (EXT4_SB(sb)->s_inode_readahead_blks-1)); > + b = block & ~(EXT4_SB(sb)->s_inode_readahead_blks-1); > + if (table > b) > + b = table; > + end = b + EXT4_SB(sb)->s_inode_readahead_blks; > + num = EXT4_INODES_PER_GROUP(sb); > + if (EXT4_HAS_RO_COMPAT_FEATURE(sb, > + EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) > + num -= le16_to_cpu(gdp->bg_itable_unused); > + table += num / inodes_per_block; > + if (end > table) > + end = table; > + while (b <= end) > + sb_breadahead(sb, b++); > + } > + > + /* > * There are other valid inodes in the buffer, this inode > * has in-inode xattrs, or we don't have this inode in memory. > * Read the block from disk. > @@ -3978,10 +3973,9 @@ make_io: > submit_bh(READ_META, bh); > wait_on_buffer(bh); > if (!buffer_uptodate(bh)) { > - ext4_error(inode->i_sb, "ext4_get_inode_loc", > - "unable to read inode block - " > - "inode=%lu, block=%llu", > - inode->i_ino, block); > + ext4_error(sb, __func__, > + "unable to read inode block - inode=%lu, " > + "block=%llu", inode->i_ino, block); > brelse(bh); > return -EIO; > } > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 9f5468f..6583aee 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -515,8 +515,10 @@ static void ext4_put_super(struct super_block *sb) > mark_buffer_dirty(sbi->s_sbh); > ext4_commit_super(sb, es, 1); > } > - if (sbi->s_proc) > + if (sbi->s_proc) { > + remove_proc_entry("inode_readahead_blks", sbi->s_proc); > remove_proc_entry(sb->s_id, ext4_proc_root); > + } > > for (i = 0; i < sbi->s_gdb_count; i++) > brelse(sbi->s_group_desc[i]); > @@ -779,6 +781,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs) > else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA) > seq_puts(seq, ",data=writeback"); > > + if (sbi->s_inode_readahead_blks != EXT4_DEF_INODE_READAHEAD_BLKS) > + seq_printf(seq, ",inode_readahead_blks=%u", > + sbi->s_inode_readahead_blks); > + > ext4_show_quota_options(seq, sb); > return 0; > } > @@ -913,6 +919,7 @@ enum { > Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota, > Opt_grpquota, Opt_extents, Opt_noextents, Opt_i_version, > Opt_mballoc, Opt_nomballoc, Opt_stripe, Opt_delalloc, Opt_nodelalloc, > + Opt_inode_readahead_blks > }; > > static match_table_t tokens = { > @@ -973,6 +980,7 @@ static match_table_t tokens = { > {Opt_resize, "resize"}, > {Opt_delalloc, "delalloc"}, > {Opt_nodelalloc, "nodelalloc"}, > + {Opt_inode_readahead_blks, "inode_readahead_blks=%u"}, > {Opt_err, NULL}, > }; > > @@ -1381,6 +1389,13 @@ set_qf_format: > case Opt_delalloc: > set_opt(sbi->s_mount_opt, DELALLOC); > break; > + case Opt_inode_readahead_blks: > + if (match_int(&args[0], &option)) > + return 0; > + if (option < 0 || option > (1 << 30)) > + return 0; > + sbi->s_inode_readahead_blks = option; > + break; > default: > printk(KERN_ERR > "EXT4-fs: Unrecognized mount option \"%s\" " > @@ -1938,6 +1953,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > sbi->s_mount_opt = 0; > sbi->s_resuid = EXT4_DEF_RESUID; > sbi->s_resgid = EXT4_DEF_RESGID; > + sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS; > sbi->s_sb_block = sb_block; > > unlock_kernel(); > @@ -2234,6 +2250,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) > if (ext4_proc_root) > sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root); > > + if (sbi->s_proc) > + proc_create_data("inode_readahead_blks", 0644, sbi->s_proc, > + &ext4_ui_proc_fops, > + &sbi->s_inode_readahead_blks); > + > bgl_lock_init(&sbi->s_blockgroup_lock); > > for (i = 0; i < db_count; i++) { > @@ -2513,8 +2534,10 @@ failed_mount2: > brelse(sbi->s_group_desc[i]); > kfree(sbi->s_group_desc); > failed_mount: > - if (sbi->s_proc) > + if (sbi->s_proc) { > + remove_proc_entry("inode_readahead_blks", sbi->s_proc); > remove_proc_entry(sb->s_id, ext4_proc_root); > + } > #ifdef CONFIG_QUOTA > for (i = 0; i < MAXQUOTAS; i++) > kfree(sbi->s_qf_names[i]); > -- > 1.5.6.1.205.ge2c7.dirty > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 163c445..922d187 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -790,6 +790,8 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) #define EXT4_DEF_RESUID 0 #define EXT4_DEF_RESGID 0 +#define EXT4_DEF_INODE_READAHEAD_BLKS 32 + /* * Default mount options */ diff --git a/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h index f92af01..94e0757 100644 --- a/fs/ext4/ext4_sb.h +++ b/fs/ext4/ext4_sb.h @@ -52,6 +52,7 @@ struct ext4_sb_info { int s_desc_per_block_bits; int s_inode_size; int s_first_ino; + unsigned int s_inode_readahead_blks; spinlock_t s_next_gen_lock; u32 s_next_generation; u32 s_hash_seed[4]; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 22fcbb6..ef4ca3d 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3833,41 +3833,6 @@ out_stop: ext4_journal_stop(handle); } -static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb, - unsigned long ino, struct ext4_iloc *iloc) -{ - ext4_group_t block_group; - unsigned long offset; - ext4_fsblk_t block; - struct ext4_group_desc *gdp; - - if (!ext4_valid_inum(sb, ino)) { - /* - * This error is already checked for in namei.c unless we are - * looking at an NFS filehandle, in which case no error - * report is needed - */ - return 0; - } - - block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb); - gdp = ext4_get_group_desc(sb, block_group, NULL); - if (!gdp) - return 0; - - /* - * Figure out the offset within the block group inode table - */ - offset = ((ino - 1) % EXT4_INODES_PER_GROUP(sb)) * - EXT4_INODE_SIZE(sb); - block = ext4_inode_table(sb, gdp) + - (offset >> EXT4_BLOCK_SIZE_BITS(sb)); - - iloc->block_group = block_group; - iloc->offset = offset & (EXT4_BLOCK_SIZE(sb) - 1); - return block; -} - /* * ext4_get_inode_loc returns with an extra refcount against the inode's * underlying buffer_head on success. If 'in_mem' is true, we have all @@ -3877,19 +3842,35 @@ static ext4_fsblk_t ext4_get_inode_block(struct super_block *sb, static int __ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc, int in_mem) { - ext4_fsblk_t block; - struct buffer_head *bh; + struct ext4_group_desc *gdp; + struct buffer_head *bh; + struct super_block *sb = inode->i_sb; + ext4_fsblk_t block; + int inodes_per_block, inode_offset; + + iloc->bh = 0; + if (!ext4_valid_inum(sb, inode->i_ino)) + return -EIO; - block = ext4_get_inode_block(inode->i_sb, inode->i_ino, iloc); - if (!block) + iloc->block_group = (inode->i_ino - 1) / EXT4_INODES_PER_GROUP(sb); + gdp = ext4_get_group_desc(sb, iloc->block_group, NULL); + if (!gdp) return -EIO; - bh = sb_getblk(inode->i_sb, block); + /* + * Figure out the offset within the block group inode table + */ + inodes_per_block = (EXT4_BLOCK_SIZE(sb) / EXT4_INODE_SIZE(sb)); + inode_offset = ((inode->i_ino - 1) % + EXT4_INODES_PER_GROUP(sb)); + block = ext4_inode_table(sb, gdp) + (inode_offset / inodes_per_block); + iloc->offset = (inode_offset % inodes_per_block) * EXT4_INODE_SIZE(sb); + + bh = sb_getblk(sb, block); if (!bh) { - ext4_error (inode->i_sb, "ext4_get_inode_loc", - "unable to read inode block - " - "inode=%lu, block=%llu", - inode->i_ino, block); + ext4_error(sb, "ext4_get_inode_loc", "unable to read " + "inode block - inode=%lu, block=%llu", + inode->i_ino, block); return -EIO; } if (!buffer_uptodate(bh)) { @@ -3917,28 +3898,12 @@ static int __ext4_get_inode_loc(struct inode *inode, */ if (in_mem) { struct buffer_head *bitmap_bh; - struct ext4_group_desc *desc; - int inodes_per_buffer; - int inode_offset, i; - ext4_group_t block_group; - int start; - - block_group = (inode->i_ino - 1) / - EXT4_INODES_PER_GROUP(inode->i_sb); - inodes_per_buffer = bh->b_size / - EXT4_INODE_SIZE(inode->i_sb); - inode_offset = ((inode->i_ino - 1) % - EXT4_INODES_PER_GROUP(inode->i_sb)); - start = inode_offset & ~(inodes_per_buffer - 1); + int i, start; - /* Is the inode bitmap in cache? */ - desc = ext4_get_group_desc(inode->i_sb, - block_group, NULL); - if (!desc) - goto make_io; + start = inode_offset & ~(inodes_per_block - 1); - bitmap_bh = sb_getblk(inode->i_sb, - ext4_inode_bitmap(inode->i_sb, desc)); + /* Is the inode bitmap in cache? */ + bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp)); if (!bitmap_bh) goto make_io; @@ -3951,14 +3916,14 @@ static int __ext4_get_inode_loc(struct inode *inode, brelse(bitmap_bh); goto make_io; } - for (i = start; i < start + inodes_per_buffer; i++) { + for (i = start; i < start + inodes_per_block; i++) { if (i == inode_offset) continue; if (ext4_test_bit(i, bitmap_bh->b_data)) break; } brelse(bitmap_bh); - if (i == start + inodes_per_buffer) { + if (i == start + inodes_per_block) { /* all other inodes are free, so skip I/O */ memset(bh->b_data, 0, bh->b_size); set_buffer_uptodate(bh); @@ -3969,6 +3934,36 @@ static int __ext4_get_inode_loc(struct inode *inode, make_io: /* + * If we need to do any I/O, try to pre-readahead extra + * blocks from the inode table. + */ + if (EXT4_SB(sb)->s_inode_readahead_blks) { + ext4_fsblk_t b, end, table; + unsigned num; + + table = ext4_inode_table(sb, gdp); + /* Make sure s_inode_readahead_blks is a power of 2 */ + while (EXT4_SB(sb)->s_inode_readahead_blks & + (EXT4_SB(sb)->s_inode_readahead_blks-1)) + EXT4_SB(sb)->s_inode_readahead_blks = + (EXT4_SB(sb)->s_inode_readahead_blks & + (EXT4_SB(sb)->s_inode_readahead_blks-1)); + b = block & ~(EXT4_SB(sb)->s_inode_readahead_blks-1); + if (table > b) + b = table; + end = b + EXT4_SB(sb)->s_inode_readahead_blks; + num = EXT4_INODES_PER_GROUP(sb); + if (EXT4_HAS_RO_COMPAT_FEATURE(sb, + EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) + num -= le16_to_cpu(gdp->bg_itable_unused); + table += num / inodes_per_block; + if (end > table) + end = table; + while (b <= end) + sb_breadahead(sb, b++); + } + + /* * There are other valid inodes in the buffer, this inode * has in-inode xattrs, or we don't have this inode in memory. * Read the block from disk. @@ -3978,10 +3973,9 @@ make_io: submit_bh(READ_META, bh); wait_on_buffer(bh); if (!buffer_uptodate(bh)) { - ext4_error(inode->i_sb, "ext4_get_inode_loc", - "unable to read inode block - " - "inode=%lu, block=%llu", - inode->i_ino, block); + ext4_error(sb, __func__, + "unable to read inode block - inode=%lu, " + "block=%llu", inode->i_ino, block); brelse(bh); return -EIO; } diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 9f5468f..6583aee 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -515,8 +515,10 @@ static void ext4_put_super(struct super_block *sb) mark_buffer_dirty(sbi->s_sbh); ext4_commit_super(sb, es, 1); } - if (sbi->s_proc) + if (sbi->s_proc) { + remove_proc_entry("inode_readahead_blks", sbi->s_proc); remove_proc_entry(sb->s_id, ext4_proc_root); + } for (i = 0; i < sbi->s_gdb_count; i++) brelse(sbi->s_group_desc[i]); @@ -779,6 +781,10 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs) else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA) seq_puts(seq, ",data=writeback"); + if (sbi->s_inode_readahead_blks != EXT4_DEF_INODE_READAHEAD_BLKS) + seq_printf(seq, ",inode_readahead_blks=%u", + sbi->s_inode_readahead_blks); + ext4_show_quota_options(seq, sb); return 0; } @@ -913,6 +919,7 @@ enum { Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota, Opt_grpquota, Opt_extents, Opt_noextents, Opt_i_version, Opt_mballoc, Opt_nomballoc, Opt_stripe, Opt_delalloc, Opt_nodelalloc, + Opt_inode_readahead_blks }; static match_table_t tokens = { @@ -973,6 +980,7 @@ static match_table_t tokens = { {Opt_resize, "resize"}, {Opt_delalloc, "delalloc"}, {Opt_nodelalloc, "nodelalloc"}, + {Opt_inode_readahead_blks, "inode_readahead_blks=%u"}, {Opt_err, NULL}, }; @@ -1381,6 +1389,13 @@ set_qf_format: case Opt_delalloc: set_opt(sbi->s_mount_opt, DELALLOC); break; + case Opt_inode_readahead_blks: + if (match_int(&args[0], &option)) + return 0; + if (option < 0 || option > (1 << 30)) + return 0; + sbi->s_inode_readahead_blks = option; + break; default: printk(KERN_ERR "EXT4-fs: Unrecognized mount option \"%s\" " @@ -1938,6 +1953,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) sbi->s_mount_opt = 0; sbi->s_resuid = EXT4_DEF_RESUID; sbi->s_resgid = EXT4_DEF_RESGID; + sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS; sbi->s_sb_block = sb_block; unlock_kernel(); @@ -2234,6 +2250,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) if (ext4_proc_root) sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root); + if (sbi->s_proc) + proc_create_data("inode_readahead_blks", 0644, sbi->s_proc, + &ext4_ui_proc_fops, + &sbi->s_inode_readahead_blks); + bgl_lock_init(&sbi->s_blockgroup_lock); for (i = 0; i < db_count; i++) { @@ -2513,8 +2534,10 @@ failed_mount2: brelse(sbi->s_group_desc[i]); kfree(sbi->s_group_desc); failed_mount: - if (sbi->s_proc) + if (sbi->s_proc) { + remove_proc_entry("inode_readahead_blks", sbi->s_proc); remove_proc_entry(sb->s_id, ext4_proc_root); + } #ifdef CONFIG_QUOTA for (i = 0; i < MAXQUOTAS; i++) kfree(sbi->s_qf_names[i]);
With modern hard drives, reading 64k takes roughly the same time as reading a 4k block. So request readahead for adjacent inode table blocks to reduce the time it takes when iterating over directories (especially when doing this in htree sort order) in a cold cache case. With this patch, the time it takes to run "git status" on a kernel tree after flushing the caches via "echo 3 > /proc/sys/vm/drop_caches" is reduced by 21%. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> --- fs/ext4/ext4.h | 2 + fs/ext4/ext4_sb.h | 1 + fs/ext4/inode.c | 134 +++++++++++++++++++++++++--------------------------- fs/ext4/super.c | 27 ++++++++++- 4 files changed, 92 insertions(+), 72 deletions(-)