From: Theodore Ts'o Subject: Re: [PATCH] ext4: improve smp scalability for inode generation Date: Wed, 8 Nov 2017 22:23:20 -0500 Message-ID: <20171109032320.dnuhngfcvldliysz@thunk.org> References: <8760bcpdc8.fsf@openvz.org> <00F078D1-39E9-4F16-8B5B-6952645846E5@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dmitry Monakhov , linux-ext4@vger.kernel.org To: Andreas Dilger Return-path: Received: from imap.thunk.org ([74.207.234.97]:54384 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751653AbdKIDXY (ORCPT ); Wed, 8 Nov 2017 22:23:24 -0500 Content-Disposition: inline In-Reply-To: <00F078D1-39E9-4F16-8B5B-6952645846E5@dilger.ca> Sender: linux-ext4-owner@vger.kernel.org List-ID: Dmitry, can you try benchmarking this patch? Thanks!! - Ted commit f0e922e7235e1b5ba6fd964e2cf8dafed3248a15 Author: Theodore Ts'o Date: Wed Nov 8 22:21:58 2017 -0500 ext4: improve smp scalability for inode generation ->s_next_generation is protected by s_next_gen_lock but its usage pattern is very primitive. We don't actually need sequentailly increasing new generation numbers, so let's use prandom_u32() instead. Reported-by: Dmitry Monakhov Signed-off-by: Theodore Ts'o diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 53ce95b52fd8..5e6d7b6f50c7 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1355,8 +1355,6 @@ struct ext4_sb_info { int s_first_ino; unsigned int s_inode_readahead_blks; unsigned int s_inode_goal; - spinlock_t s_next_gen_lock; - u32 s_next_generation; u32 s_hash_seed[4]; int s_def_hash_version; int s_hash_unsigned; /* 3 if hash should be signed, 0 if not */ diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index ee823022aa34..da79eb5dba40 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -1138,9 +1138,7 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir, inode->i_ino); goto out; } - spin_lock(&sbi->s_next_gen_lock); - inode->i_generation = sbi->s_next_generation++; - spin_unlock(&sbi->s_next_gen_lock); + inode->i_generation = prandom_u32(); /* Precompute checksum seed for inode metadata */ if (ext4_has_metadata_csum(sb)) { diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index 144bbda2b808..98ad8172dfd3 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "ext4_jbd2.h" #include "ext4.h" #include @@ -157,10 +158,8 @@ static long swap_inode_boot_loader(struct super_block *sb, inode->i_ctime = inode_bl->i_ctime = current_time(inode); - spin_lock(&sbi->s_next_gen_lock); - inode->i_generation = sbi->s_next_generation++; - inode_bl->i_generation = sbi->s_next_generation++; - spin_unlock(&sbi->s_next_gen_lock); + inode->i_generation = prandom_u32(); + inode_bl->i_generation = prandom_u32(); ext4_discard_preallocations(inode); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 3a278faf5868..9f2e3eb5131f 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3982,8 +3982,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) } sbi->s_gdb_count = db_count; - get_random_bytes(&sbi->s_next_generation, sizeof(u32)); - spin_lock_init(&sbi->s_next_gen_lock); timer_setup(&sbi->s_err_report, print_daily_error_info, 0);