Re: sluggish system responsiveness under higher IO load
From: Matthias Dahl
Date: Sun Aug 06 2006 - 09:52:55 EST
> I'd suggest that you generate a kernel profile while the sluggishness is
> happening.
Done...
profile 1: (emerge of three huge packages which caused quite some IO)
ffffffff80232650 __wake_up 23 0.2396
ffffffff803427a0 vgacon_cursor 23 0.0395
ffffffff8020ba40 free_hot_cold_page 24 0.0652
ffffffff8020be90 find_vma 25 0.2232
ffffffff8020c9b0 __wake_up_bit 25 0.5208
ffffffff80301800 journal_add_journal_head 25 0.0601
ffffffff803424e0 vgacon_scroll 26 0.0478
ffffffff802eb970 __ext3_get_inode_loc 27 0.0312
ffffffff802fd8e0 journal_dirty_metadata 27 0.0456
ffffffff80207500 kmem_cache_free 28 0.2917
ffffffff80211d90 do_select 30 0.0216
ffffffff8020d420 bit_waitqueue 32 0.1429
ffffffff8020bbb0 fget_light 34 0.1635
ffffffff8026b97f thread_return 35 0.1211
ffffffff80268d50 system_call 36 0.2748
ffffffff8020a580 kmem_cache_alloc 39 0.6094
ffffffff8020cae0 vm_normal_page 42 0.2188
ffffffff8020bf00 __make_request 43 0.0384
ffffffff8020b600 __find_get_block 47 0.0979
ffffffff802eb5c0 ext3_mark_iloc_dirty 48 0.0508
ffffffff8020a0f0 get_page_from_freelist 50 0.0428
ffffffff802fba50 do_get_write_access 55 0.0382
ffffffff80209050 __link_path_walk 56 0.0132
ffffffff803a63a0 scsi_request_fn 57 0.0604
ffffffff8026b0c0 memcpy 59 0.3352
ffffffff8020ccf0 __delay 69 2.1562
ffffffff80208350 __handle_mm_fault 78 0.0269
ffffffff802075e0 unmap_vmas 93 0.0501
ffffffff80208ea0 __d_lookup 95 0.2199
ffffffff8026ad30 clear_page 100 1.7544
ffffffff80341880 vgacon_set_cursor_size 103 0.4023
ffffffff8020a920 do_page_fault 105 0.0443
ffffffff80207560 find_get_page 106 0.9464
ffffffff80207d20 copy_page_range 111 0.0701
ffffffff8026ad70 copy_page 157 0.7009
ffffffff80212cd0 __do_softirq 189 1.0739
ffffffff803a0430 scsi_dispatch_cmd 459 0.7172
ffffffff8026afda copy_user_generic_c 854 22.4737
ffffffff80270e00 default_idle 49571 516.3646
0000000000000000 total 54590 0.0232
profile 2: (emerge of recent kernel sources- huge, causes quite some IO too)
ffffffff8020ff40 generic_permission 57 0.2227
ffffffff8020ccf0 __delay 58 1.8125
ffffffff802149a0 rb_insert_color 58 0.2417
ffffffff802af8b0 free_page_and_swap_cache 63 1.3125
ffffffff8020ccb0 put_page 66 1.0312
ffffffff803a63a0 scsi_request_fn 67 0.0710
ffffffff80234c60 unix_poll 69 0.3920
ffffffff8020b600 __find_get_block 74 0.1542
ffffffff80268d50 system_call 81 0.6183
ffffffff8020e220 memscan 88 1.8333
ffffffff80224820 __up_read 92 0.5227
ffffffff802fba50 do_get_write_access 95 0.0660
ffffffff80207500 kmem_cache_free 99 1.0312
ffffffff80223d40 find_next_zero_bit 100 0.6944
ffffffff8020d6a0 strncpy_from_user 103 1.2875
ffffffff80211d90 do_select 104 0.0747
ffffffff8020c9b0 __wake_up_bit 117 2.4375
ffffffff8026b97f thread_return 120 0.4152
ffffffff8020a580 kmem_cache_alloc 143 2.2344
ffffffff8026b0c0 memcpy 154 0.8750
ffffffff8020a0f0 get_page_from_freelist 155 0.1327
ffffffff8020b260 page_remove_rmap 172 2.6875
ffffffff80221320 copy_process 175 0.0315
ffffffff80207560 find_get_page 190 1.6964
ffffffff8020be90 find_vma 198 1.7679
ffffffff80211900 do_wp_page 249 0.2132
ffffffff80209050 __link_path_walk 315 0.0740
ffffffff8026afda copy_user_generic_c 325 8.5526
ffffffff80212cd0 __do_softirq 452 2.5682
ffffffff80208350 __handle_mm_fault 479 0.1654
ffffffff80208ea0 __d_lookup 510 1.1806
ffffffff8026ad30 clear_page 519 9.1053
ffffffff803a0430 scsi_dispatch_cmd 576 0.9000
ffffffff8020a920 do_page_fault 712 0.3007
ffffffff8020cae0 vm_normal_page 814 4.2396
ffffffff8026ad70 copy_page 1929 8.6116
ffffffff802075e0 unmap_vmas 2362 1.2726
ffffffff80207d20 copy_page_range 2683 1.6938
ffffffff80270e00 default_idle 45081 469.5938
0000000000000000 total 64216 0.0273
I hope this helps.
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