Whatever would the cached include except for the file pages?
0
votes
0
answers
58
views
Environment: a standby/idle running physical system with RHEL 6.9
Symptom: We have done some dd tests in order to observe the change of the buffers/cached size in the free -m cmd. After we had cleaned up the buffers & cache, the buffers were just empty whereas the cached was still with 111MB. And then the cached had increased about nearly 60MB when we dd the block devices.
Notes: We know that some storage metadatas e.g. superblocks would be stored in the buffers but not the caches
So my two sub-questions are the followings:
1. Why would the cached column size still have 111MB after cleaning up the buffers & cache?
2. Why would the cached column size "obviously" increase during the dd process with the block devices?
#
#
# free -m
total used free shared buffers cached
Mem: 96646 23673 72973 0 21233 759
-/+ buffers/cache: 1680 94966
Swap: 16383 0 16383
#
#
#
# echo 3 > /proc/sys/vm/drop_caches
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 1098 95547 0 0 111
-/+ buffers/cache: 986 95659
Swap: 16383 0 16383
#
#
# vmstat 1 6
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 340 97844368 872 114688 1 1 61 22 0 0 1 0 99 0 0
0 0 340 97844496 872 114748 0 0 8 0 1046 282 0 0 100 0 0
0 0 340 97844496 872 114748 0 0 8 1 1041 245 0 0 100 0 0
0 0 340 97844656 872 114748 0 0 8 0 1043 248 0 0 100 0 0
0 0 340 97844656 872 114748 0 0 8 1 1038 255 0 0 100 0 0
0 1 340 97844536 900 114728 0 0 0 88 1038 312 0 0 94 6 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 1097 95548 0 0 111
-/+ buffers/cache: 984 95661
Swap: 16383 0 16383
#
#
#
# vmstat 1 6
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 340 97844032 924 114724 1 1 61 22 0 0 1 0 99 0 0
0 0 340 97844256 924 114744 0 0 8 0 1051 240 0 0 100 0 0
0 0 340 97844320 924 114748 0 0 8 1 1040 262 0 0 100 0 0
0 0 340 97844192 924 114748 0 0 8 0 1085 387 0 0 100 0 0
0 0 340 97844320 924 114748 0 0 8 1 1042 278 0 0 100 0 0
0 0 340 97844336 948 114724 0 0 8 88 1050 382 0 0 100 0 0
#
#
#
#
# nohup dd if=/dev/mapper/vgroot-Lvopenv of=/dev/mapper/vgroot-test_d1 skip=1000 bs=512k &
31265
# nohup: appending output to `nohup.out'
#
#
# vmstat 1 6
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 0 340 95727896 2003476 175072 1 1 61 22 0 0 1 0 99 0 0
0 1 340 95206576 2511252 175320 0 0 253704 1 2037 2228 0 7 86 7 0
0 1 340 94687136 3017104 175248 0 0 252932 0 2028 2249 0 7 87 5 0
1 0 340 94162088 3528332 175184 0 0 255748 13 2769 3694 0 7 88 5 0
1 1 340 93647632 4029624 175316 0 0 250792 32 2090 2361 0 7 87 6 0
0 1 340 93156560 4507884 175300 0 0 239060 53 3246 4805 0 7 84 9 0
#
#
#
# vmstat 1 16
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 1 340 91163136 6448656 175376 1 1 61 22 0 0 1 0 99 0 0
0 1 340 90679296 6918568 175328 0 0 235016 84 3089 4673 0 7 82 10 0
1 0 340 90181824 7403024 175372 0 0 242312 1 1992 2139 0 7 81 12 0
0 1 340 89652680 7918120 175352 0 0 257416 0 2052 2285 0 7 88 5 0
0 1 340 89132208 8424744 174992 0 0 253448 1 2075 2370 0 7 87 5 0
1 0 340 88643328 8900780 175212 0 0 238088 0 1988 2108 0 7 88 6 0
0 1 340 88139840 9391552 175028 0 0 245132 109 3326 4918 0 7 85 8 0
0 1 340 87653032 9865536 175032 0 0 236928 28 3286 4714 0 7 84 9 0
1 0 340 87162032 10343672 175088 0 0 239168 1 1996 2135 0 7 88 6 0
1 1 340 86628672 10862840 175244 0 0 259464 0 2062 2269 0 7 87 5 0
0 1 340 86111256 11366648 175280 0 0 251912 1 2027 2203 0 7 88 5 0
0 1 340 85647328 11818128 175116 0 0 225672 76 3178 4722 0 7 84 9 0
1 0 340 85119456 12331920 175352 0 0 257036 1 2045 2266 0 7 88 5 0
1 1 340 84605016 12832912 175108 0 0 250628 0 2023 2223 0 7 87 5 0
0 1 340 84103872 13320768 175124 0 0 243976 1 1996 2143 0 7 87 6 0
1 0 340 83574232 13836432 175068 0 0 257800 0 2055 2257 0 7 88 5 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 18136 78509 0 16535 171
-/+ buffers/cache: 1430 95215
Swap: 16383 0 16383
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 19348 77297 0 17714 171
-/+ buffers/cache: 1463 95182
Swap: 16383 0 16383
#
#
#
# vmstat 1 8
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 1 340 76894032 20335952 175340 1 1 61 22 0 0 1 0 99 0 0
0 1 340 76765144 20462952 175320 0 0 63504 62141 2936 3832 0 3 83 13 0
0 2 340 76542304 20675944 174984 0 0 106504 100072 4100 6171 0 5 86 9 0
0 1 340 76384016 20831592 174540 0 0 77832 86633 3442 4367 0 5 74 21 0
1 2 340 76203216 21006304 174852 0 0 87560 63616 3575 5025 0 4 80 16 0
2 0 340 75999744 21205200 174716 0 0 99464 109757 4353 4825 0 6 69 25 0
0 1 340 75887632 21317888 174624 0 0 56072 66444 2902 3058 0 4 67 30 0
1 0 340 75776488 21427168 174860 0 0 54832 53877 2462 2719 0 3 86 11 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 23456 73190 0 21710 171
-/+ buffers/cache: 1574 95071
Swap: 16383 0 16383
#
#
#
# vmstat 1 8
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
1 2 340 73209824 23919680 174788 1 1 61 22 0 0 1 0 99 0 0
0 3 340 73024896 24100928 175080 0 0 90640 58949 3819 4529 0 4 70 26 0
1 2 340 72831408 24288564 174660 0 0 93972 116933 4019 5393 0 5 71 23 0
0 5 340 72720272 24396836 175212 0 0 53980 48204 2674 3136 0 3 67 30 0
0 1 340 72571424 24543292 174976 0 0 73224 114093 3475 3974 0 5 66 29 0
0 1 340 72448096 24663100 174936 0 0 59912 62160 2826 3558 0 3 87 10 0
2 0 340 72315760 24791336 174712 0 0 64264 64189 2990 3924 0 3 87 10 0
1 0 340 72151496 24952988 175168 0 0 80784 80852 3604 4461 0 5 78 17 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 26734 69911 0 24901 170
-/+ buffers/cache: 1662 94983
Swap: 16383 0 16383
#
#
#
# vmstat 1 8
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 1 340 64158176 32734544 175056 1 1 61 22 0 0 1 0 99 0 0
1 1 340 63928852 32954576 175112 0 0 110216 91508 4238 6208 0 5 79 16 0
2 2 340 63731188 33147344 174416 0 0 96392 65021 4082 5205 0 5 69 27 0
0 2 340 63559684 33315152 175000 0 0 83720 57344 3594 4304 0 4 73 23 0
2 4 340 63375412 33494368 174696 0 0 89736 53849 3797 4833 0 4 60 37 0
0 2 340 63287548 33580396 175388 0 0 42888 155148 2723 2397 0 5 74 21 0
1 1 340 63205204 33662312 175368 0 0 41096 41445 2235 2548 0 2 75 23 0
0 1 340 63015216 33847664 175244 0 0 92552 94760 3939 5725 0 5 78 18 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 36143 60502 0 34060 170
-/+ buffers/cache: 1912 94733
Swap: 16383 0 16383
#
#
#
# vmstat 1 8
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 3 340 58571068 38169084 175056 1 1 61 22 0 0 1 0 99 0 0
0 1 340 58416972 38323708 174736 0 0 77320 99065 3467 3472 0 5 78 17 0
0 3 340 58350100 38389268 175332 0 0 32776 29044 1946 2020 0 2 62 36 0
0 1 340 58184636 38550036 175160 0 0 80392 78693 3303 4483 0 4 86 10 0
0 1 340 58022008 38707732 175244 0 0 78856 82880 3281 4339 0 4 87 10 0
0 1 340 57873524 38853140 175500 0 0 72712 70449 3134 4027 0 4 87 10 0
0 1 340 57742212 38981140 175248 0 0 64008 62160 2847 3613 0 3 87 10 0
0 1 340 57556304 39161388 174828 0 0 90120 91193 3542 4991 0 4 78 17 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 42214 54431 0 39966 171
-/+ buffers/cache: 2077 94568
Swap: 16383 0 16383
#
#
#
+ Done nohup dd if=/dev/mapper/vgroot-Lvopenv of=/dev/mapper/vgroot-test_d1 skip=1000 bs=512k
#
#
#
# vmstat 1 8
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 340 76560704 20466772 175368 1 1 61 22 0 0 1 0 99 0 0
0 0 340 76560704 20466772 175368 0 0 8 1 1049 249 0 0 93 7 0
0 0 340 76560688 20466772 175368 0 0 8 0 1086 393 0 0 100 0 0
0 0 340 76560432 20466796 175356 0 0 8 85 1053 387 0 0 100 0 0
0 0 340 76560720 20466796 175368 0 0 8 104 1060 256 0 0 100 0 0
0 0 340 76560720 20466796 175368 0 0 8 1 1052 249 0 0 100 0 0
0 0 340 76560856 20466796 175368 0 0 8 0 1042 242 0 0 100 0 0
0 0 340 76560856 20466796 175368 0 0 8 1 1045 280 0 0 100 0 0
#
#
#
# free -m
total used free shared buffers cached
Mem: 96646 21879 74766 0 19987 171
-/+ buffers/cache: 1721 94925
Swap: 16383 0 16383
#
#
Asked by lylklb
(285 rep)
Oct 30, 2024, 11:51 PM
Last activity: Nov 13, 2024, 08:40 AM
Last activity: Nov 13, 2024, 08:40 AM