CPU IDLE baixa pode ser causada por vários fatores, incluindo: RAM insuficiente ou unidade de disco rígido lenta
mas em nossa memória RAM do servidor RHEL temos RAM suficiente, mas no dmesg encontramos alguns erros sobre a unidade de discos
nossa suspeita é sobre os discos como por exemplo sdk e sdc e isso porque vimos erros de dmesg como[sdk] tag#0 Add. Sense: Unrecovered read error
aqui os detalhes do sarcomando que mostra os valores CPU IDLE
09:43:56 AM CPU %user %nice %system %iowait %steal %idle
09:44:01 AM all 98.57 0.00 0.62 0.00 0.00 0.80
09:44:06 AM all 98.26 0.00 0.92 0.01 0.00 0.81
09:44:11 AM all 97.29 0.00 1.66 0.01 0.00 1.03
09:44:16 AM all 92.81 0.00 6.06 0.03 0.00 1.10
09:44:21 AM all 92.31 0.00 6.43 0.05 0.00 1.21
Average: all 95.85 0.00 3.14 0.02 0.00 0.99
09:44:21 AM CPU %user %nice %system %iowait %steal %idle
09:44:22 AM all 96.52 0.00 3.10 0.00 0.00 0.38
09:44:22 AM 0 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 1 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 2 100.00 0.00 0.00 0.00 0.00 0.00
09:44:22 AM 3 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 4 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 5 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 6 97.98 0.00 2.02 0.00 0.00 0.00
09:44:22 AM 7 97.98 0.00 2.02 0.00 0.00 0.00
09:44:22 AM 8 98.99 0.00 1.01 0.00 0.00 0.00
09:44:22 AM 9 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 10 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 11 98.02 0.00 0.99 0.00 0.00 0.99
09:44:22 AM 12 97.00 0.00 1.00 0.00 0.00 2.00
09:44:22 AM 13 96.97 0.00 3.03 0.00 0.00 0.00
09:44:22 AM 14 98.02 0.00 0.99 0.00 0.00 0.99
09:44:22 AM 15 94.00 0.00 6.00 0.00 0.00 0.00
09:44:22 AM 16 83.00 0.00 16.00 0.00 0.00 1.00
09:44:22 AM 17 98.00 0.00 1.00 0.00 0.00 1.00
09:44:22 AM 18 96.97 0.00 2.02 0.00 0.00 1.01
09:44:22 AM 19 96.00 0.00 4.00 0.00 0.00 0.00
09:44:22 AM 20 97.98 0.00 1.01 0.00 0.00 1.01
09:44:22 AM 21 95.05 0.00 4.95 0.00 0.00 0.00
09:44:22 AM 22 94.95 0.00 5.05 0.00 0.00 0.00
09:44:22 AM 23 98.99 0.00 1.01 0.00 0.00 0.00
09:44:22 AM 24 98.99 0.00 1.01 0.00 0.00 0.00
09:44:22 AM 25 99.00 0.00 1.00 0.00 0.00 0.00
09:44:22 AM 26 98.99 0.00 1.01 0.00 0.00 0.00
09:44:22 AM 27 98.99 0.00 1.01 0.00 0.00 0.00
09:44:22 AM 28 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 29 98.00 0.00 2.00 0.00 0.00 0.00
09:44:22 AM 30 94.95 0.00 5.05 0.00 0.00 0.00
09:44:22 AM 31 97.03 0.00 1.98 0.00 0.00 0.99
09:44:22 AM 32 98.02 0.00 1.98 0.00 0.00 0.00
09:44:22 AM 33 99.00 0.00 1.00 0.00 0.00 0.00
09:44:22 AM 34 98.00 0.00 1.00 0.00 0.00 1.00
09:44:22 AM 35 97.98 0.00 2.02 0.00 0.00 0.00
09:44:22 AM 36 94.00 0.00 5.00 0.00 0.00 1.00
09:44:22 AM 37 98.02 0.00 0.99 0.00 0.00 0.99
09:44:22 AM 38 97.98 0.00 1.01 0.00 0.00 1.01
09:44:22 AM 39 89.00 0.00 11.00 0.00 0.00 0.00
09:44:22 AM 40 83.00 0.00 13.00 0.00 0.00 4.00
09:44:22 AM 41 97.00 0.00 3.00 0.00 0.00 0.00
09:44:22 AM 42 91.92 0.00 8.08 0.00 0.00 0.00
09:44:22 AM 43 94.06 0.00 5.94 0.00 0.00 0.00
09:44:22 AM 44 92.93 0.00 7.07 0.00 0.00 0.00
09:44:22 AM 45 97.00 0.00 3.00 0.00 0.00 0.00
09:44:22 AM 46 99.00 0.00 1.00 0.00 0.00 0.00
09:44:22 AM 47 98.99 0.00 1.01 0.00 0.00 0.00
sar -B 2 5
09:44:24 AM pgpgin/s pgpgout/s fault/s majflt/s pgfree/s pgscank/s pgscand/s pgsteal/s %vmeff
09:44:26 AM 14852.00 71776.00 101443.50 0.00 216420.00 0.00 0.00 0.00 0.00
09:44:28 AM 14336.00 184.00 5123.00 0.00 47167.50 0.00 0.00 0.00 0.00
09:44:30 AM 14418.00 203778.00 67194.50 0.00 132952.50 0.00 0.00 0.00 0.00
09:44:32 AM 14352.00 220796.00 2475.00 0.00 59666.00 0.00 0.00 0.00 0.00
09:44:34 AM 13318.00 56996.00 16290.00 0.00 9599.00 0.00 0.00 0.00 0.00
Average: 14255.20 110706.00 38505.20 0.00 93161.00 0.00 0.00 0.00 0.00
do vmstatcomando
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
65 0 3505188 6265864 4828612 304096576 0 0 137 127 0 0 49 1 50 0 0
63 1 3505188 6068484 4828660 304294848 0 0 12292 41500 95782 88751 98 2 1 0 0
66 0 3505188 5933464 4828672 304429248 0 0 14668 130968 85788 90844 97 2 1 0 0
r: O número de processos aguardando tempo de execução.
das mensagens do kernel, obtemos:
[117426425.532990] blk_update_request: critical medium error, dev sdc, sector 116127985
[117426431.038365] sd 0:0:3:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[117426431.038374] sd 0:0:3:0: [sdc] tag#0 Sense Key : Medium Error [current] [descriptor]
[117426431.038378] sd 0:0:3:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[117426431.038383] sd 0:0:3:0: [sdc] tag#0 CDB: Read(16) 88 00 00 00 00 00 06 eb f8 f0 00 00 00 08 00 00
[117426431.038386] blk_update_request: critical medium error, dev sdc, sector 116127985
[139602560.596832] traps: polkitd[27641] general protection ip:7f7996318cf2 sp:7ffe7a28e5b0 error:0 in libmozjs-17.0.so[7f79961da000+3b3000]
[144770588.094226] sd 0:0:11:0: [sdk] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[144770588.094238] sd 0:0:11:0: [sdk] tag#0 Sense Key : Medium Error [current] [descriptor]
[144770588.094242] sd 0:0:11:0: [sdk] tag#0 Add. Sense: Unrecovered read error
[144770588.094248] sd 0:0:11:0: [sdk] tag#0 CDB: Read(16) 88 00 00 00 00 00 01 15 20 00 00 00 02 00 00 00
então, com base na saída acima, faz sentido que a causa raiz do CPU IDLE muito baixo seja porque há erros nos discos conforme obtemos as mensagens do kernel?
Com base nos carimbos de data e hora, quase um ano se passou entre os dois erros de disco em seus logs, então não, eles não são o motivo pelo qual seu sistema não está ocioso.
Como um aparte, observe que
não é preciso: em
vmstat, arcoluna mostra o número de processos executáveis, ou seja, o número de processos em execução ou aguardando para serem executados. Se você tiver muitas CPUs lógicas, um número alto aqui não será um problema.