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Message-ID: <20160813214825.GA31667@lst.de>
Date:	Sat, 13 Aug 2016 23:48:25 +0200
From:	Christoph Hellwig <hch@....de>
To:	Dave Chinner <david@...morbit.com>
Cc:	Ye Xiaolong <xiaolong.ye@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bob Peterson <rpeterso@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, LKP <lkp@...org>,
	Christoph Hellwig <hch@....de>
Subject: Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6%
	regression

On Sat, Aug 13, 2016 at 02:30:54AM +0200, Christoph Hellwig wrote:
> Below is a patch I hacked up this morning to do just that.  It passes
> xfstests, but I've not done any real benchmarking with it.  If the
> reduced lookup overhead in it doesn't help enough we'll need to some
> sort of look aside cache for the information, but I hope that we
> can avoid that.  And yes, it's a rather large patch - but the old
> path was so entangled that I couldn't come up with something lighter.

Hi Fengguang or Xiaolong,

any chance to add this thread to a lkp run?  I've played around with
Dave's simplied xfs_io run, and while the end result for 1k block
size looks pretty similar in terms of execution time and throughput
the profiles look much better.  For 512 byte or 1 byte tests the
tests completes a lot faster too.

Here is the perf report output for a 1k block size run, the first
item directly related to the block mapping shows up is
xfs_file_iomap_begin_delay at .75%.  Although I'm a bit worried
up up_/down_read showing up so much.  While we take a ilock and
iolock a lot they should be mostly uncontended for such a single
threaded write, so the overhead seems a bit worrisome.

(FYI, the tree this was tested on also has the mark_page_accessed
and pagefault_disable fixes applied)

# To display the perf.data header info, please use --header/--header-only options.
#
# Samples: 7K of event 'cpu-clock'
# Event count (approx.): 1909250000
#
# Overhead       Command      Shared Object                                 Symbol
# ........  ............  .................  .....................................
#
    37.71%       swapper  [kernel.kallsyms]  [k] native_safe_halt                 
     9.85%  kworker/u8:5  [kernel.kallsyms]  [k] __copy_user_nocache              
     2.83%        xfs_io  [kernel.kallsyms]  [k] copy_user_generic_string         
     2.33%        xfs_io  [kernel.kallsyms]  [k] __memset                         
     2.23%        xfs_io  [kernel.kallsyms]  [k] __block_commit_write.isra.34     
     1.73%        xfs_io  [kernel.kallsyms]  [k] down_write                       
     1.64%        xfs_io  [kernel.kallsyms]  [k] up_write                         
     1.39%        xfs_io  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore      
     1.23%        xfs_io  [kernel.kallsyms]  [k] entry_SYSCALL_64_fastpath        
     1.18%        xfs_io  [kernel.kallsyms]  [k] __mark_inode_dirty               
     1.18%        xfs_io  [kernel.kallsyms]  [k] _raw_spin_lock                   
     1.15%  kworker/u8:5  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore      
     1.13%        xfs_io  [kernel.kallsyms]  [k] __block_write_begin_int          
     1.10%        xfs_io  [kernel.kallsyms]  [k] mark_buffer_dirty                
     1.07%        xfs_io  [kernel.kallsyms]  [k] __radix_tree_lookup              
     1.01%   kworker/0:2  [kernel.kallsyms]  [k] end_buffer_async_write           
     0.97%        xfs_io  [kernel.kallsyms]  [k] unlock_page                      
     0.92%   kworker/0:2  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore      
     0.89%        xfs_io  [kernel.kallsyms]  [k] iov_iter_copy_from_user_atomic   
     0.84%        xfs_io  [kernel.kallsyms]  [k] generic_write_end                
     0.80%        xfs_io  [kernel.kallsyms]  [k] get_page_from_freelist           
     0.80%        xfs_io  [kernel.kallsyms]  [k] xfs_perag_put                    
     0.79%        xfs_io  [kernel.kallsyms]  [k] __add_to_page_cache_locked       
     0.75%        xfs_io  libc-2.19.so       [.] __libc_pwrite                    
     0.72%        xfs_io  [kernel.kallsyms]  [k] xfs_file_iomap_begin_delay.isra.5
     0.71%        xfs_io  [kernel.kallsyms]  [k] iomap_write_actor                
     0.67%        xfs_io  [kernel.kallsyms]  [k] pagecache_get_page               
     0.64%        xfs_io  [kernel.kallsyms]  [k] balance_dirty_pages_ratelimited  
     0.64%        xfs_io  [kernel.kallsyms]  [k] vfs_write                        
     0.63%  kworker/u8:5  [kernel.kallsyms]  [k] clear_page_dirty_for_io          
     0.62%        xfs_io  [kernel.kallsyms]  [k] xfs_file_write_iter              
     0.60%        xfs_io  [kernel.kallsyms]  [k] __vfs_write                      
     0.55%        xfs_io  [kernel.kallsyms]  [k] page_waitqueue                   
     0.54%        xfs_io  [kernel.kallsyms]  [k] xfs_perag_get                    
     0.52%        xfs_io  [kernel.kallsyms]  [k] __wake_up_bit                    
     0.52%        xfs_io  [kernel.kallsyms]  [k] radix_tree_tag_set               
     0.50%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_do_writepage                 
     0.50%        xfs_io  [kernel.kallsyms]  [k] iov_iter_advance                 
     0.47%        xfs_io  [kernel.kallsyms]  [k] kmem_cache_alloc                 
     0.46%        xfs_io  [kernel.kallsyms]  [k] xfs_file_buffered_aio_write      
     0.46%        xfs_io  [kernel.kallsyms]  [k] xfs_iunlock                      
     0.45%  kworker/u8:5  [kernel.kallsyms]  [k] __wake_up_bit                    
     0.45%        xfs_io  [kernel.kallsyms]  [k] find_get_entry                   
     0.45%        xfs_io  [kernel.kallsyms]  [k] xfs_bmap_search_multi_extents    
     0.41%        xfs_io  [kernel.kallsyms]  [k] xfs_iext_bno_to_ext              
     0.39%        xfs_io  [kernel.kallsyms]  [k] iomap_apply                      
     0.39%        xfs_io  [kernel.kallsyms]  [k] xfs_file_aio_write_checks        
     0.38%        xfs_io  [kernel.kallsyms]  [k] xfs_ilock                        
     0.38%        xfs_io  [kernel.kallsyms]  [k] xfs_inode_set_eofblocks_tag      
     0.37%        xfs_io  [kernel.kallsyms]  [k] xfs_bmap_search_extents          
     0.30%        xfs_io  [kernel.kallsyms]  [k] file_update_time                 
     0.29%        xfs_io  [kernel.kallsyms]  [k] __fget_light                     
     0.27%        xfs_io  [kernel.kallsyms]  [k] rw_verify_area                   
     0.26%  kworker/u8:5  [kernel.kallsyms]  [k] unlock_page                      
     0.26%        xfs_io  xfs_io             [.] pwrite_f                         
     0.25%        xfs_io  [kernel.kallsyms]  [k] iomap_file_buffered_write        
     0.25%        xfs_io  [kernel.kallsyms]  [k] node_dirty_ok                    
     0.25%        xfs_io  [kernel.kallsyms]  [k] xfs_bmbt_to_iomap                
     0.24%   kworker/0:2  [kernel.kallsyms]  [k] xfs_destroy_ioend                
     0.24%        xfs_io  [kernel.kallsyms]  [k] __xfs_bmbt_get_all               
     0.24%        xfs_io  [kernel.kallsyms]  [k] iov_iter_fault_in_readable       
     0.22%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_start_buffer_writeback       
     0.22%        xfs_io  [kernel.kallsyms]  [k] fsnotify                         
     0.22%        xfs_io  [kernel.kallsyms]  [k] sys_pwrite64                     
     0.22%        xfs_io  [kernel.kallsyms]  [k] xfs_file_iomap_begin             
     0.21%  kworker/u8:5  [kernel.kallsyms]  [k] pmem_do_bvec                     
     0.21%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_map_at_offset                
     0.18%  kworker/u8:5  [kernel.kallsyms]  [k] write_cache_pages                
     0.18%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_map_buffer                   
     0.17%  kworker/u8:5  [kernel.kallsyms]  [k] __test_set_page_writeback        
     0.17%        xfs_io  [kernel.kallsyms]  [k] __alloc_pages_nodemask           
     0.17%        xfs_io  [kernel.kallsyms]  [k] __fsnotify_parent                
     0.17%        xfs_io  [kernel.kallsyms]  [k] block_write_end                  
     0.17%        xfs_io  [kernel.kallsyms]  [k] iomap_write_begin                
     0.17%        xfs_io  [kernel.kallsyms]  [k] iov_iter_init                    
     0.17%        xfs_io  [kernel.kallsyms]  [k] percpu_up_read                   
     0.17%        xfs_io  [kernel.kallsyms]  [k] radix_tree_lookup_slot           
     0.16%        xfs_io  [kernel.kallsyms]  [k] create_empty_buffers             
     0.16%        xfs_io  [kernel.kallsyms]  [k] timespec_trunc                   
     0.16%        xfs_io  [kernel.kallsyms]  [k] wait_for_stable_page             
     0.16%        xfs_io  [kernel.kallsyms]  [k] xfs_get_extsz_hint               
     0.14%   kworker/0:2  [kernel.kallsyms]  [k] test_clear_page_writeback        
     0.14%  kworker/u8:5  [kernel.kallsyms]  [k] release_pages                    
     0.13%        xfs_io  [kernel.kallsyms]  [k] iomap_write_end                  
     0.13%        xfs_io  [kernel.kallsyms]  [k] xfs_bmbt_get_startoff            
     0.12%  kworker/u8:5  [kernel.kallsyms]  [k] dec_zone_page_state              
     0.12%        xfs_io  [kernel.kallsyms]  [k] alloc_page_buffers               
     0.12%        xfs_io  [kernel.kallsyms]  [k] generic_write_checks             
     0.12%        xfs_io  [kernel.kallsyms]  [k] percpu_down_read                 
     0.12%        xfs_io  [kernel.kallsyms]  [k] release_pages                    
     0.12%        xfs_io  [kernel.kallsyms]  [k] set_bh_page                      
     0.12%        xfs_io  [kernel.kallsyms]  [k] xfs_find_bdev_for_inode          
     0.12%        xfs_io  xfs_io             [.] do_pwrite                        
     0.10%  kworker/u8:5  [kernel.kallsyms]  [k] mark_buffer_async_write          
     0.10%  kworker/u8:5  [kernel.kallsyms]  [k] page_waitqueue                   
     0.10%        xfs_io  [kernel.kallsyms]  [k] PageHuge                         
     0.10%        xfs_io  [kernel.kallsyms]  [k] add_to_page_cache_lru            
     0.09%   kworker/0:2  [kernel.kallsyms]  [k] end_page_writeback               
     0.09%  kworker/u8:5  [kernel.kallsyms]  [k] find_get_pages_tag               
     0.09%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_start_page_writeback         
     0.09%        xfs_io  [kernel.kallsyms]  [k] create_page_buffers              
     0.09%        xfs_io  [kernel.kallsyms]  [k] page_mapping                     
     0.09%        xfs_io  [kernel.kallsyms]  [k] xfs_bmbt_get_all                 
     0.09%        xfs_io  [kernel.kallsyms]  [k] xfs_file_iomap_end               
     0.08%  kworker/u8:5  [kernel.kallsyms]  [k] inc_node_page_state              
     0.08%  kworker/u8:5  [kernel.kallsyms]  [k] inc_zone_page_state              
     0.08%  kworker/u8:5  [kernel.kallsyms]  [k] page_mapping                     
     0.08%  kworker/u8:5  [kernel.kallsyms]  [k] page_mkclean                     
     0.08%        xfs_io  [kernel.kallsyms]  [k] __sb_start_write                 
     0.08%        xfs_io  [kernel.kallsyms]  [k] current_kernel_time64            
     0.07%   kworker/0:2  [kernel.kallsyms]  [k] __wake_up_bit                    
     0.07%  kworker/u8:5  [kernel.kallsyms]  [k] page_mapped                      
     0.07%        xfs_io  [kernel.kallsyms]  [k] __lru_cache_add                  
     0.07%        xfs_io  [kernel.kallsyms]  [k] current_fs_time                  
     0.07%        xfs_io  [kernel.kallsyms]  [k] grab_cache_page_write_begin      
     0.07%        xfs_io  [kernel.kallsyms]  [k] xfs_iext_get_ext                 
     0.05%  kworker/u8:5  [kernel.kallsyms]  [k] pmem_make_request                
     0.05%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_add_to_ioend                 
     0.05%        xfs_io  [kernel.kallsyms]  [k] __fdget                          
     0.05%        xfs_io  [kernel.kallsyms]  [k] __find_get_block_slow            
     0.05%        xfs_io  [kernel.kallsyms]  [k] __set_page_dirty                 
     0.05%        xfs_io  [kernel.kallsyms]  [k] alloc_buffer_head                
     0.05%        xfs_io  [kernel.kallsyms]  [k] radix_tree_lookup                
     0.05%        xfs_io  [kernel.kallsyms]  [k] radix_tree_tagged                
     0.05%        xfs_io  [kernel.kallsyms]  [k] xfs_bmbt_get_blockcount          
     0.05%        xfs_io  [kernel.kallsyms]  [k] xfs_fsb_to_db                    
     0.04%   kworker/0:2  [kernel.kallsyms]  [k] dec_zone_page_state              
     0.04%  kworker/u8:5  [kernel.kallsyms]  [k] dec_node_page_state              
     0.04%        xfs_io  [kernel.kallsyms]  [k] __radix_tree_preload             
     0.04%        xfs_io  [kernel.kallsyms]  [k] __sb_end_write                   
     0.03%   kworker/0:2  [kernel.kallsyms]  [k] dec_node_page_state              
     0.03%   kworker/0:2  [kernel.kallsyms]  [k] inc_node_page_state              
     0.03%   kworker/0:2  [kernel.kallsyms]  [k] page_mapping                     
     0.03%  kworker/u8:5  [kernel.kallsyms]  [k] radix_tree_next_chunk            
     0.03%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_fsb_to_db                    
     0.03%        xfs_io  [kernel.kallsyms]  [k] _raw_spin_lock_irqsave           
     0.03%        xfs_io  [kernel.kallsyms]  [k] cache_alloc_refill               
     0.03%        xfs_io  [kernel.kallsyms]  [k] lru_cache_add                    
     0.01%   kworker/0:2  [kernel.kallsyms]  [k] cache_reap                       
     0.01%   kworker/0:2  [kernel.kallsyms]  [k] mempool_free                     
     0.01%   kworker/0:2  [kernel.kallsyms]  [k] page_waitqueue                   
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] bio_add_page                     
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] kmem_cache_alloc                 
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] lru_add_drain_cpu                
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] mempool_alloc                    
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] pagevec_lookup_tag               
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] queue_delayed_work_on            
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] queue_work_on                    
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] run_timer_softirq                
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] update_group_capacity            
     0.01%  kworker/u8:5  [kernel.kallsyms]  [k] xfs_trans_reserve                
     0.01%       swapper  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore      
     0.01%        xfs_io  [kernel.kallsyms]  [k] _cond_resched                    
     0.01%        xfs_io  [kernel.kallsyms]  [k] mod_zone_page_state              
     0.01%        xfs_io  [kernel.kallsyms]  [k] pagevec_lru_move_fn              
     0.01%        xfs_io  [kernel.kallsyms]  [k] radix_tree_maybe_preload         
     0.01%        xfs_io  [kernel.kallsyms]  [k] unmap_underlying_metadata        
     0.01%        xfs_io  [kernel.kallsyms]  [k] xfs_bmap_worst_indlen            
     0.01%        xfs_io  ld-2.19.so         [.] 0x000000000000d866               
     0.01%        xfs_io  libc-2.19.so       [.] 0x000000000008a8da               
     0.01%        xfs_io  xfs_io             [.] pwrite64@plt                     


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