From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760920Ab0FRAAp (ORCPT ); Thu, 17 Jun 2010 20:00:45 -0400 Received: from mga14.intel.com ([143.182.124.37]:48201 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757325Ab0FRAAn (ORCPT ); Thu, 17 Jun 2010 20:00:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.53,434,1272870000"; d="scan'208";a="290222744" Subject: [PATCH v3 2/2] tmpfs: Make tmpfs scalable with percpu_counter for used blocks From: Tim Chen To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Andi Kleen , Hugh Dickins , yanmin.zhang@intel.com Content-Type: text/plain; charset="UTF-8" Date: Thu, 17 Jun 2010 16:56:33 -0700 Message-ID: <1276818993.9661.82.camel@schen9-DESK> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The current implementation of tmpfs is not scalable. We found that stat_lock is contended by multiple threads when we need to get a new page, leading to useless spinning inside this spin lock. This patch makes use of the percpu_counter library to maintain local count of used blocks to speed up getting and returning of pages. So the acquisition of stat_lock is unnecessary for getting and returning blocks, improving the performance of tmpfs on system with large number of cpus. On a 4 socket 32 core NHM-EX system, we saw improvement of 270%. Signed-off-by: Tim Chen include/linux/shmem_fs.h | 3 ++- mm/shmem.c | 40 +++++++++++++++++----------------------- 2 files changed, 19 insertions(+), 24 deletions(-) diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index e164291..399be5a 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -3,6 +3,7 @@ #include #include +#include /* inode in-kernel data */ @@ -23,7 +24,7 @@ struct shmem_inode_info { struct shmem_sb_info { unsigned long max_blocks; /* How many blocks are allowed */ - unsigned long free_blocks; /* How many are left for allocation */ + struct percpu_counter used_blocks; /* How many are allocated */ unsigned long max_inodes; /* How many inodes are allowed */ unsigned long free_inodes; /* How many are left for allocation */ spinlock_t stat_lock; /* Serialize shmem_sb_info changes */ diff --git a/mm/shmem.c b/mm/shmem.c index eef4ebe..c6adedf 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -28,6 +28,7 @@ #include #include #include +#include #include static struct vfsmount *shm_mnt; @@ -233,10 +234,10 @@ static void shmem_free_blocks(struct inode *inode, long pages) { struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); if (sbinfo->max_blocks) { - spin_lock(&sbinfo->stat_lock); - sbinfo->free_blocks += pages; + percpu_counter_add(&sbinfo->used_blocks, -pages); + spin_lock(&inode->i_lock); inode->i_blocks -= pages*BLOCKS_PER_PAGE; - spin_unlock(&sbinfo->stat_lock); + spin_unlock(&inode->i_lock); } } @@ -416,19 +417,17 @@ static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long if (sgp == SGP_READ) return shmem_swp_map(ZERO_PAGE(0)); /* - * Test free_blocks against 1 not 0, since we have 1 data + * Test used_blocks against 1 less max_blocks, since we have 1 data * page (and perhaps indirect index pages) yet to allocate: * a waste to allocate index if we cannot allocate data. */ if (sbinfo->max_blocks) { - spin_lock(&sbinfo->stat_lock); - if (sbinfo->free_blocks <= 1) { - spin_unlock(&sbinfo->stat_lock); + if (percpu_counter_compare(&sbinfo->used_blocks, (sbinfo->max_blocks - 1)) > 0) return ERR_PTR(-ENOSPC); - } - sbinfo->free_blocks--; + percpu_counter_inc(&sbinfo->used_blocks); + spin_lock(&inode->i_lock); inode->i_blocks += BLOCKS_PER_PAGE; - spin_unlock(&sbinfo->stat_lock); + spin_unlock(&inode->i_lock); } spin_unlock(&info->lock); @@ -1385,17 +1384,16 @@ repeat: shmem_swp_unmap(entry); sbinfo = SHMEM_SB(inode->i_sb); if (sbinfo->max_blocks) { - spin_lock(&sbinfo->stat_lock); - if (sbinfo->free_blocks == 0 || + if ((percpu_counter_compare(&sbinfo->used_blocks, sbinfo->max_blocks) > 0) || shmem_acct_block(info->flags)) { - spin_unlock(&sbinfo->stat_lock); spin_unlock(&info->lock); error = -ENOSPC; goto failed; } - sbinfo->free_blocks--; + percpu_counter_inc(&sbinfo->used_blocks); + spin_lock(&inode->i_lock); inode->i_blocks += BLOCKS_PER_PAGE; - spin_unlock(&sbinfo->stat_lock); + spin_unlock(&inode->i_lock); } else if (shmem_acct_block(info->flags)) { spin_unlock(&info->lock); error = -ENOSPC; @@ -1791,17 +1789,16 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf) buf->f_type = TMPFS_MAGIC; buf->f_bsize = PAGE_CACHE_SIZE; buf->f_namelen = NAME_MAX; - spin_lock(&sbinfo->stat_lock); if (sbinfo->max_blocks) { buf->f_blocks = sbinfo->max_blocks; - buf->f_bavail = buf->f_bfree = sbinfo->free_blocks; + buf->f_bavail = buf->f_bfree = + sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks); } if (sbinfo->max_inodes) { buf->f_files = sbinfo->max_inodes; buf->f_ffree = sbinfo->free_inodes; } /* else leave those fields 0 like simple_statfs */ - spin_unlock(&sbinfo->stat_lock); return 0; } @@ -2250,7 +2247,6 @@ static int shmem_remount_fs(struct super_block *sb, int *flags, char *data) { struct shmem_sb_info *sbinfo = SHMEM_SB(sb); struct shmem_sb_info config = *sbinfo; - unsigned long blocks; unsigned long inodes; int error = -EINVAL; @@ -2258,9 +2254,8 @@ static int shmem_remount_fs(struct super_block *sb, int *flags, char *data) return error; spin_lock(&sbinfo->stat_lock); - blocks = sbinfo->max_blocks - sbinfo->free_blocks; inodes = sbinfo->max_inodes - sbinfo->free_inodes; - if (config.max_blocks < blocks) + if (config.max_blocks < percpu_counter_sum(&sbinfo->used_blocks)) goto out; if (config.max_inodes < inodes) goto out; @@ -2277,7 +2272,6 @@ static int shmem_remount_fs(struct super_block *sb, int *flags, char *data) error = 0; sbinfo->max_blocks = config.max_blocks; - sbinfo->free_blocks = config.max_blocks - blocks; sbinfo->max_inodes = config.max_inodes; sbinfo->free_inodes = config.max_inodes - inodes; @@ -2352,7 +2346,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent) #endif spin_lock_init(&sbinfo->stat_lock); - sbinfo->free_blocks = sbinfo->max_blocks; + percpu_counter_init(&sbinfo->used_blocks, 0); sbinfo->free_inodes = sbinfo->max_inodes; sb->s_maxbytes = SHMEM_MAX_BYTES;