From: Mingming Cao Subject: Re: [PATCH] ext4: dir inode reservation V3 Date: Mon, 19 Nov 2007 18:01:01 -0800 Message-ID: <1195524061.4177.17.camel@localhost.localdomain> References: <4739B0C0.3060907@suse.de> Reply-To: cmm@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: coyli@suse.de Return-path: Received: from e6.ny.us.ibm.com ([32.97.182.146]:46292 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759536AbXKTCBE (ORCPT ); Mon, 19 Nov 2007 21:01:04 -0500 In-Reply-To: <4739B0C0.3060907@suse.de> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue, 2007-11-13 at 22:12 +0800, Coly Li wrote: > Basic idea of my dir inode reservation patch can be found here, > http://lists.openwall.net/linux-ext4/2007/11/05/3 > > 1, What does dir inode reservation do > Dir inode reservation tries to reserve several inodes in inodes table for a directory when this > directory is created. When create new file under this directory, try to allocate inode from the > reserved inodes area. This is called as dir_ireserve inode allocator. > Thanks for the update. Let me try to understand your method: So the basic idea is not do linear inode allocation for directory? Inode structure block for directory file is only coming from block 0, N, N +N,... where the number of skipped blocks N is stored in the in-core superblock structure. When ever need to allocate an inode for directory, skip N reserved bits (space for N*16 inodes) if the previous block is already allocated. That way place two directories with the hole of N*16 inodes structures, then allow files under the first directory stay closer with their parent directory. Is this correct? > 4, Dir inode reservation is optional > Dir inode reservation is optional, you can use -o followed by one of these options to enable dir > inode reservation during mount ext4 file system: > dir_ireserve=low > dir_ireserve=normal > dir_ireserve=high Would be nice to pass the tuning info low/normal/high(16/64/128 blocks correspondingly) via something else rather than mount options. > Currently, 'low' reserves 15 file inodes for each directory, 'normal' reserves 31 inodes and 'high' > reserves 127 inodes. Reserving more than 127 inodes does not help to performance obviously. > > > 5, Performance number > On a Core-Duo, 2MB DDM memory, 7200 RPM SATA PC, I built a 50GB ext4 partition, and tried to create > 50000 directories, and create 15 (1KB) files in each directory alternatively. After a remount, I > tried to remove all the directories and files recursively by a 'rm -rf'. Bellow is the benchmark result, > normal ext4 ext4 with dir inode reservation > mount options: -o data=writeback -o data=writeback,dir_ireserve=low > Create dirs: real 0m49.101s real 2m59.703s > Create files: real 24m17.962s real 21m8.161s > Unlink all: real 24m43.788s real 17m29.862s > Creating dirs with dir inode reservation is slower than normal ext4 as predicted, because allocating > directory inodes in non-linear order will cause extra hard disk seeking and block I/O. Hmm...I suspect there is bug in your patch, the extra seek should not contribute to 4 times slower > > #include > @@ -478,6 +480,75 @@ static int find_group_other(struct super_block *sb, struct inode *parent, > return -1; > } > > +static int ext4_ino_from_ireserve(handle_t *handle, struct inode *dir, > + int mode, ext4_group_t *group, unsigned long *ino) > +{ > + struct super_block *sb; > + struct ext4_sb_info *sbi; > + struct ext4_group_desc *gdp = NULL; > + struct buffer_head *gdp_bh = NULL, *bitmap_bh = NULL; > + ext4_group_t ires_group = *group; > + unsigned long ires_ino; > + int i, bit; > + > + sb = dir->i_sb; > + sbi = EXT4_SB(sb); > + > + /* if the inode number is not for directory, > + * only try to allocate after directory's inode > + */ > + if (!S_ISDIR(mode)) { > + *ino = dir->i_ino % EXT4_INODES_PER_GROUP(sb); > + return 0; > + } > + > + /* reserve inodes for new directory */ > + for (i = 0; i < sbi->s_groups_count; i++) { > + gdp = ext4_get_group_desc(sb, ires_group, &gdp_bh); > + if (!gdp) > + goto fail; > + bit = 0; > +try_same_group: > + if (bit < EXT4_INODES_PER_GROUP(sb)) { > + brelse(bitmap_bh); > + bitmap_bh = read_inode_bitmap(sb, ires_group); > + if (!bitmap_bh) > + goto fail; > + > + BUFFER_TRACE(bitmap_bh, "get_write_access"); > + if (ext4_journal_get_write_access( > + handle, bitmap_bh) != 0) > + goto fail; > + if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, ires_group), > + bit, bitmap_bh->b_data)) { > + /* we won it */ > + BUFFER_TRACE(bitmap_bh, > + "call ext4_journal_dirty_metadata"); > + if (ext4_journal_dirty_metadata(handle, > + bitmap_bh) != 0) > + goto fail; > + ires_ino = bit; > + goto find; > + } > + /* we lost it */ > + jbd2_journal_release_buffer(handle, bitmap_bh); > + bit += sbi->s_dir_ireserve_nr; > + goto try_same_group; > + } > + if (++ires_group == sbi->s_groups_count) > + ires_group = 0; > + } > + goto fail; > +find: > + brelse(bitmap_bh); > + *group = ires_group; > + *ino = ires_ino; > + return 0; > +fail: > + brelse(bitmap_bh); > + return -ENOSPC; > +} > + > /* > * There are two policies for allocating an inode. If the new inode is > * a directory, then a forward search is made for a block group with both > @@ -543,6 +614,12 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode * dir, int mode) > > ino = 0; > > + if (test_opt(sb, DIR_IRESERVE)) { > + err = ext4_ino_from_ireserve(handle, dir, > + mode, &group, &ino); > + if ((!err) && S_ISDIR(mode)) > + goto got; > + } So you are calling ext4_ino_from_ireserve() inside a loop iterate all block groups? I think this is bug, it should move outside of the loop. > repeat_in_this_group: > ino = ext4_find_next_zero_bit((unsigned long *) > bitmap_bh->b_data, EXT4_INODES_PER_GROUP(sb), ino); > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index b626339..9b873b7 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -884,6 +884,7 @@ enum { > Opt_commit, Opt_journal_update, Opt_journal_inum, Opt_journal_dev, > Opt_journal_checksum, Opt_journal_async_commit, > Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback, > + Opt_dir_ireserve_low, Opt_dir_ireserve_normal, Opt_dir_ireserve_high, > Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota, > Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota, > Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota, > @@ -929,6 +930,9 @@ static match_table_t tokens = { > {Opt_data_journal, "data=journal"}, > {Opt_data_ordered, "data=ordered"}, > {Opt_data_writeback, "data=writeback"}, > + {Opt_dir_ireserve_low, "dir_ireserve=low"}, > + {Opt_dir_ireserve_normal, "dir_ireserve=normal"}, > + {Opt_dir_ireserve_high, "dir_ireserve=high"}, > {Opt_offusrjquota, "usrjquota="}, > {Opt_usrjquota, "usrjquota=%s"}, > {Opt_offgrpjquota, "grpjquota="}, > @@ -1311,6 +1315,18 @@ clear_qf_name: > return 0; > sbi->s_stripe = option; > break; > + case Opt_dir_ireserve_low: > + set_opt(sbi->s_mount_opt, DIR_IRESERVE); > + sbi->s_dir_ireserve_nr = EXT4_DIR_IRESERVE_LOW; > + break; > + case Opt_dir_ireserve_normal: > + set_opt(sbi->s_mount_opt, DIR_IRESERVE); > + sbi->s_dir_ireserve_nr = EXT4_DIR_IRESERVE_NORMAL; > + break; > + case Opt_dir_ireserve_high: > + set_opt(sbi->s_mount_opt, DIR_IRESERVE); > + sbi->s_dir_ireserve_nr = EXT4_DIR_IRESERVE_HIGH; > + break; > default: > printk (KERN_ERR > "EXT4-fs: Unrecognized mount option \"%s\" " > diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h > index bcdb59d..88f5173 100644 > --- a/include/linux/ext4_fs.h > +++ b/include/linux/ext4_fs.h > @@ -92,6 +92,13 @@ struct ext4_allocation_request { > #define EXT4_GOOD_OLD_FIRST_INO 11 > > /* > + * Macro-instructions used to reserve inodes for directories > + */ > +#define EXT4_DIR_IRESERVE_LOW 16 > +#define EXT4_DIR_IRESERVE_NORMAL 64 > +#define EXT4_DIR_IRESERVE_HIGH 128 > + > +/* > * Maximal count of links to a file > */ > #define EXT4_LINK_MAX 65000 > @@ -502,6 +509,7 @@ do { \ > #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */ > #define EXT4_MOUNT_DELALLOC 0x2000000 /* Delalloc support */ > #define EXT4_MOUNT_MBALLOC 0x4000000 /* Buddy allocation support */ > +#define EXT4_MOUNT_DIR_IRESERVE 0x10000000/* dir inode reservation */ > /* Compatibility, for having both ext2_fs.h and ext4_fs.h included at once */ > #ifndef _LINUX_EXT2_FS_H > #define clear_opt(o, opt) o &= ~EXT4_MOUNT_##opt > diff --git a/include/linux/ext4_fs_sb.h b/include/linux/ext4_fs_sb.h > index 744e746..790b0cf 100644 > --- a/include/linux/ext4_fs_sb.h > +++ b/include/linux/ext4_fs_sb.h > @@ -147,6 +147,8 @@ struct ext4_sb_info { > > /* locality groups */ > struct ext4_locality_group *s_locality_groups; > + /* number of inodes we reserve in a directory */ > + int s_dir_ireserve_nr; > }; > #define EXT4_GROUP_INFO(sb, group) \ > EXT4_SB(sb)->s_group_info[(group) >> EXT4_DESC_PER_BLOCK_BITS(sb)] \ > >