On Mon, Jul 26, 2010 at 03:41:11PM +1000, Nick Piggin wrote: > On Fri, Jul 23, 2010 at 05:01:00AM +1000, Nick Piggin wrote: > > I'm pleased to announce I have a git tree up of my vfs scalability work. > > > > git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin.git > > http://git.kernel.org/?p=linux/kernel/git/npiggin/linux-npiggin.git > > Pushed several fixes and improvements > o XFS bugs fixed by Dave > o dentry and inode stats bugs noticed by Dave > o vmscan shrinker bugs fixed by KOSAKI san > o compile bugs noticed by John > o a few attempts to improve powerpc performance (eg. reducing smp_rmb()) > o scalability improvments for rename_lock Yet another result on my small 2s8c Opteron. This time, the re-aim benchmark configured as described here: http://ertos.nicta.com.au/publications/papers/Chubb_Williams_05.pdf It is using ext2 on ramdisk and an IO intensive workload, with fsync activity. I did 10 runs on each, and took the max jobs/sec of each run. N Min Max Median Avg Stddev x 10 2598750 2735122 2665384.6 2653353.8 46421.696 + 10 3337297.3 3484687.5 3410689.7 3397763.8 49994.631 Difference at 95.0% confidence 744410 +/- 45327.3 28.0554% +/- 1.7083% Average is 2653K jobs/s for vanilla, versus 3398K jobs/s for vfs-scalem or 28% speedup. The profile is interesting. It is known to be inode_lock intensive, but we also see here that it is do_lookup intensive, due to cacheline bouncing in common elements of path lookups. Vanilla: # Overhead Symbol # ........ ...... # 7.63% [k] __d_lookup | |--88.59%-- do_lookup |--9.75%-- __lookup_hash |--0.89%-- d_lookup 7.17% [k] _raw_spin_lock | |--11.07%-- _atomic_dec_and_lock | | | |--53.73%-- dput | --46.27%-- iput | |--9.85%-- __mark_inode_dirty | | | |--46.25%-- ext2_new_inode | |--25.32%-- __set_page_dirty | |--18.27%-- nobh_write_end | |--6.91%-- ext2_new_blocks | |--3.12%-- ext2_unlink | |--7.69%-- ext2_new_inode | |--6.84%-- insert_inode_locked | ext2_new_inode | |--6.56%-- new_inode | ext2_new_inode | |--5.61%-- writeback_single_inode | sync_inode | generic_file_fsync | ext2_fsync | |--5.13%-- dput |--3.75%-- generic_delete_inode |--3.56%-- __d_lookup |--3.53%-- ext2_free_inode |--3.40%-- sync_inode |--2.71%-- d_instantiate |--2.36%-- d_delete |--2.25%-- inode_sub_bytes |--1.84%-- file_move |--1.52%-- file_kill |--1.36%-- ext2_new_blocks |--1.34%-- ext2_create |--1.34%-- d_alloc |--1.11%-- do_lookup |--1.07%-- iput |--1.05%-- __d_instantiate 4.19% [k] mutex_spin_on_owner | |--99.92%-- __mutex_lock_slowpath | mutex_lock | | | |--56.45%-- do_unlinkat | | sys_unlink | | | --43.55%-- do_last | do_filp_open 2.96% [k] _atomic_dec_and_lock | |--58.18%-- dput |--31.02%-- mntput_no_expire |--3.30%-- path_put |--3.09%-- iput |--2.69%-- link_path_walk |--1.02%-- fput 2.73% [k] copy_user_generic_string 2.67% [k] __mark_inode_dirty 2.65% [k] link_path_walk 2.63% [k] mark_buffer_dirty 1.72% [k] __memcpy 1.62% [k] generic_getxattr 1.50% [k] acl_permission_check 1.30% [k] __find_get_block 1.30% [k] __memset 1.17% [k] ext2_find_entry 1.09% [k] ext2_new_inode 1.06% [k] system_call 1.01% [k] kmem_cache_free 1.00% [k] dput In vfs-scale, most of the spinlock contention and path lookup cost is gone. Contention for parent i_mutex (and d_lock) for creat/unlink operations is now at the top of the profile. A lot of the spinlock overhead seems to be not contention so much as the the cost of the atomics. Down at 3% it is much less a problem than it was though. We may run into a bit of contention on the per-bdi inode dirty/io list lock, with just a single ramdisk device (dirty/fsync activity will hit this lock), but it is really not worth worrying about at the moment. # Overhead Symbol # ........ ...... # 5.67% [k] mutex_spin_on_owner | |--99.96%-- __mutex_lock_slowpath | mutex_lock | | | |--58.63%-- do_unlinkat | | sys_unlink | | | --41.37%-- do_last | do_filp_open 3.93% [k] __mark_inode_dirty 3.43% [k] copy_user_generic_string 3.31% [k] link_path_walk 3.15% [k] mark_buffer_dirty 3.11% [k] _raw_spin_lock | |--11.03%-- __mark_inode_dirty |--10.54%-- ext2_new_inode |--7.60%-- ext2_free_inode |--6.33%-- inode_sub_bytes |--6.27%-- ext2_new_blocks |--5.80%-- generic_delete_inode |--4.09%-- ext2_create |--3.62%-- writeback_single_inode |--2.92%-- sync_inode |--2.81%-- generic_drop_inode |--2.46%-- iput |--1.86%-- dput |--1.80%-- __dquot_alloc_space |--1.61%-- __mutex_unlock_slowpath |--1.59%-- generic_file_fsync |--1.57%-- __d_instantiate |--1.55%-- __set_page_dirty_buffers |--1.36%-- d_alloc_and_lookup |--1.23%-- do_path_lookup |--1.10%-- ext2_free_blocks 2.13% [k] __memset 2.12% [k] __memcpy 1.98% [k] __d_lookup_rcu 1.46% [k] generic_getxattr 1.44% [k] ext2_find_entry 1.41% [k] __find_get_block 1.27% [k] kmem_cache_free 1.25% [k] ext2_new_inode 1.23% [k] system_call 1.02% [k] ext2_add_link 1.01% [k] strncpy_from_user 0.96% [k] kmem_cache_alloc 0.95% [k] find_get_page 0.94% [k] sysret_check 0.88% [k] __d_lookup 0.75% [k] ext2_delete_entry 0.70% [k] generic_file_aio_read 0.67% [k] generic_file_buffered_write 0.63% [k] ext2_new_blocks 0.62% [k] __percpu_counter_add 0.59% [k] __bread 0.58% [k] __wake_up_bit 0.58% [k] __mutex_lock_slowpath 0.56% [k] __ext2_write_inode 0.55% [k] ext2_get_blocks -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . 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