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SubjectRE: The cause of the "VM" performance problem with 2.4.X
Date
> This (rather hastily tested) patch against 2.4.9 should give O(n)
> behaviour in write_unlocked_buffers(). Does it help?

Yes, it helps quite a bit. Still not as good as I'd like: I don't
dare try lots of disks yet :-(

Here is the new lockmeter output (8 parallel mkfs processes on 4X
Lion to different disks, entire mkfs execution time).

Looks like blkdev_put() holds kernel_flag for way too long.

Looking under the lru_list_lock, you can see several functions that hold
the spinlock > 300ms. getblk only holds it for a max of 7ms, but it gets
called so much it dominates the execution time.


____________________________________________________________________________
_______________
System: Linux vanmaren.slc.unisys.com 2.4.8 #13 SMP Wed Aug 22 18:34:15 UTC
2001 ia64
Total counts

All (4) CPUs
Selecting locks that meet ALL of the following:
utilization : > 1.00%


Start time: Wed Aug 22 19:10:17 2001
End time: Wed Aug 22 19:11:30 2001
Delta Time: 72.67 sec.
Hash table slots in use: 254.
Global read lock slots in use: 101.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - -
SPINLOCKS HOLD WAIT
UTIL CON MEAN( MAX ) MEAN( MAX )(% CPU) TOTAL NOWAIT SPIN
RJECT NAME

29.4% 4.8us(2809ms) 40us(1780ms)(62.4%) 15255259 70.6% 29.4%
0.00% *TOTAL*

3.9% 0.06% 29us(5958us) 0us 96244 100% 0%
0.06% global_bh_lock
3.9% 0.06% 29us(5958us) 0us 96244 100% 0%
0.06% bh_action+0x40

6.6% 9.1% 1.3us( 111us) 14us( 234us)( 1.7%) 3773504 90.9% 9.1%
0% io_request_lock
0.00% 10.8% 0.5us( 2.6us) 13us( 68us)(0.00%) 655 89.2% 10.8%
0% __get_request_wait+0xb0
5.4% 3.4% 2.1us( 77us) 9.8us( 234us)(0.21%) 1846091 96.6% 3.4%
0% __make_request+0x270
0.05% 18.6% 2.6us( 111us) 6.2us( 123us)(0.01%) 13228 81.4% 18.6%
0% ahc_linux_isr+0x3d0
0.77% 14.4% 0.3us( 3.8us) 16us( 226us)( 1.4%) 1845765 85.6% 14.4%
0% blk_get_queue+0x50
0.00% 18.6% 3.7us( 19us) 12us( 117us)(0.00%) 575 81.4% 18.6%
0% generic_unplug_device+0x40
0.29% 22.3% 11us( 92us) 11us( 154us)(0.02%) 18488 77.7% 22.3%
0% scsi_dispatch_cmd+0x2b0
0.01% 18.5% 0.4us( 3.3us) 5.8us( 132us)(0.01%) 16157 81.5% 18.5%
0% scsi_finish_command+0x60
0.05% 17.5% 2.1us( 95us) 6.3us( 95us)(0.01%) 16157 82.5% 17.5%
0% scsi_queue_next_request+0x40
0.07% 11.8% 2.9us( 37us) 3.4us( 107us)(0.00%) 16388 88.2% 11.8%
0% scsi_request_fn+0x510

8.0% 0.45% 54us(2809ms) 25us(2394us)(0.00%) 107442 99.5% 0.45%
0% kernel_flag
0.00% 0% 0.4us( 0.5us) 0us 3 100% 0%
0% acct_process+0x140
0.00% 56.2% 5.1us( 12us) 559us(2394us)(0.00%) 16 43.8% 56.2%
0% blkdev_open+0xb0
7.6% 20.0% 553ms(2809ms) 46us( 59us)(0.00%) 10 80.0% 20.0%
0% blkdev_put+0xd0
0.00% 0% 2.3us( 3.3us) 0us 8 100% 0%
0% chrdev_open+0xc0
0.00% 0% 52us( 63us) 0us 3 100% 0%
0% do_exit+0x1f0
0.00% 0% 0.5us( 0.9us) 0us 63 100% 0%
0% ext2_discard_prealloc+0x50
0.00% 14.9% 1.9us( 41us) 14us( 28us)(0.00%) 74 85.1% 14.9%
0% ext2_get_block+0xb0
0.00% 0% 7.0us( 8.2us) 0us 6 100% 0%
0% fsync_dev+0x80
0.00% 0.40% 1.3us( 9.9us) 20us( 57us)(0.00%) 1260 99.6% 0.40%
0% posix_lock_file+0x2d0
0.19% 0.15% 4.9us( 383us) 8.2us( 87us)(0.00%) 27984 99.9% 0.15%
0% real_lookup+0x200
0.00% 27.3% 6.4us( 17us) 15us( 20us)(0.00%) 11 72.7% 27.3%
0% schedule+0x8c0
0.00% 0% 219us(1031us) 0us 10 100% 0%
0% sync_old_buffers+0x50
0.00% 22.2% 5.4us( 11us) 30us( 34us)(0.00%) 9 77.8% 22.2%
0% sys_ioctl+0x90
0.03% 0.54% 0.3us( 176us) 14us( 580us)(0.00%) 73179 99.5% 0.54%
0% sys_lseek+0xf0
0.11% 0.48% 20us( 586us) 34us( 172us)(0.00%) 4165 99.5% 0.48%
0% tty_write+0x4a0
0.02% 0.16% 24us( 64us) 2.4us( 2.4us)(0.00%) 640 99.8% 0.16%
0% vfs_readdir+0x1c0
0.00% 0% 31us( 31us) 0us 1 100% 0%
0% vfs_statfs+0xc0

78.3% 87.2% 12us(1780ms) 43us(1780ms)(60.6%) 4681456 12.8% 87.2%
0% lru_list_lock
4.8% 30.0% 350ms(1780ms) 61us( 77us)(0.00%) 10 70.0% 30.0%
0% __invalidate_buffers+0x40
50.8% 78.5% 15us(7412us) 34us( 366ms)(21.6%) 2382129 21.5% 78.5%
0% getblk+0x40
0.79% 66.7% 64ms( 366ms) 36us( 97us)(0.00%) 9 33.3% 66.7%
0% kupdate+0x190
6.8% 97.0% 2.2us(1204us) 34us( 366ms)(25.2%) 2241541 3.0% 97.0%
0% refile_buffer+0x30
0.80% 90.9% 15us(3212us) 401us(1780ms)( 4.9%) 38766 9.1% 90.9%
0% sync_old_buffers+0x100
3.4% 12.5% 77ms( 327ms) 22us( 54us)(0.00%) 32 87.5% 12.5%
0% wait_for_locked_buffers+0x40
11.0% 18.6% 420us( 344ms) 7344us(1780ms)( 8.9%) 18969 81.4% 18.6%
0% write_unlocked_buffers+0x40

1.3% 0.45% 0.4us(3859us) 2.0us( 180us)(0.01%) 2381262 99.6% 0.45%
0% getblk+0x2b0

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - -
RWLOCK READS HOLD MAX RDR BUSY PERIOD WAIT
UTIL CON MEAN RDRS MEAN( MAX ) MEAN( MAX )( %CPU) TOTAL
NOWAIT SPIN NAME

0.00% 1.2us( 1.5us)(0.00%) 229513
100% 0.00% *TOTAL*

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - -
RWLOCK WRITES HOLD WAIT (ALL) WAIT (WW)
UTIL CON MEAN( MAX ) MEAN( MAX )( %CPU) MEAN( MAX ) TOTAL
NOWAIT SPIN( WW ) NAME

36.6% 0% 9.0us(3880us) 0us 0us 2942425
100% 0%( 0%) hash_table_lock
1.1% 0% 1.4us( 6.5us) 0us 0us 560296
100% 0%( 0%) __invalidate_buffers+0x250
35.5% 0% 11us(3880us) 0us 0us 2382129
100% 0%( 0%) getblk+0x60
____________________________________________________________________________
_____________________________________________
Number of read locks found=0
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