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SubjectRe: Performance gap between 2.2.14 and 2.4.0-test4 kernels
This is interesting, i thought it was only IDE that didnt scale well in
2.[34], looks like the problem is more generic than that.

I cc'ed this to linux-raid.

Glenn

> Gianluca Cecchi wrote:
>
>
> The system:
>
> MB: Supermicro P6SBU (Adaptec 7890 on board)
> CPU: 1 pentium III 500 MHz
> Mem: 256Mb
>
> 1x9.1Gb IBM DNES-309170W disk on fast/se channel
> 4x18.2Gb IBM DNES-318350W on ultra2 channel
> The 18.2 Gb disks are in raid0 software. Below the /etc/raidtab file:
>
> raiddev /dev/md0
> raid-level 0
> nr-raid-disks 4
> persistent-superblock 1
> chunk-size 128
> device /dev/sdb1
> raid-disk 0
> device /dev/sdc1
> raid-disk 1
> device /dev/sdd1
> raid-disk 2
> device /dev/sde1
> raid-disk 3
>
> output of dmesg related to scsi conf (in 2.4.0-test4 boot):
>
> md.c: sizeof(mdp_super_t) = 4096
> (scsi0) <Adaptec AIC-7890/1 Ultra2 SCSI host adapter> found at PCI
> 0/14/0
> (scsi0) Wide Channel, SCSI ID=7, 32/255 SCBs
> (scsi0) Downloading sequencer code... 392 instructions downloaded
> scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.2.1/5.2.0
> <Adaptec AIC-7890/1 Ultra2 SCSI host adapter>
> scsi : 1 host.
> (scsi0:0:5:0) Synchronous at 10.0 Mbyte/sec, offset 15.
> Vendor: SONY Model: SDT-9000 Rev: 0400
> Type: Sequential-Access ANSI SCSI revision: 02
> (scsi0:0:6:0) Synchronous at 40.0 Mbyte/sec, offset 31.
> Vendor: IBM Model: DNES-309170W Rev: SA30
> Type: Direct-Access ANSI SCSI revision: 03
> Detected scsi disk sda at scsi0, channel 0, id 6, lun 0
> (scsi0:0:8:0) Synchronous at 80.0 Mbyte/sec, offset 31.
> Vendor: IBM Model: DNES-318350W Rev: SA30
> Type: Direct-Access ANSI SCSI revision: 03
> Detected scsi disk sdb at scsi0, channel 0, id 8, lun 0
> (scsi0:0:9:0) Synchronous at 80.0 Mbyte/sec, offset 31.
> Vendor: IBM Model: DNES-318350W Rev: SA30
> Type: Direct-Access ANSI SCSI revision: 03
> Detected scsi disk sdc at scsi0, channel 0, id 9, lun 0
> (scsi0:0:10:0) Synchronous at 80.0 Mbyte/sec, offset 31.
> Vendor: IBM Model: DNES-318350W Rev: SA30
> Type: Direct-Access ANSI SCSI revision:
> 03
> Detected scsi disk sdd at scsi0, channel 0, id 10, lun 0
> (scsi0:0:12:0) Synchronous at 80.0 Mbyte/sec, offset 31.
> Vendor: IBM Model: DNES-318350W Rev: SA30
> Type: Direct-Access ANSI SCSI revision: 03
> Detected scsi disk sde at scsi0, channel 0, id 12, lun 0
> scsi : detected 5 SCSI disks total.
> SCSI device sda: hdwr sector= 512 bytes. Sectors= 17916240 [8748 MB]
> [8.7 GB]
> Partition check:
> sda: sda1 sda2 < sda5 sda6 sda7 >
> SCSI device sdb: hdwr sector= 512 bytes. Sectors= 35843670 [17501 MB]
> [17.5 GB]
> sdb: sdb1
> SCSI device sdc: hdwr sector= 512 bytes. Sectors= 35843670 [17501 MB]
> [17.5 GB]
> sdc: sdc1
> SCSI device sdd: hdwr sector= 512 bytes. Sectors= 35843670 [17501 MB]
> [17.5 GB]
> sdd: sdd1
> SCSI device sde: hdwr sector= 512 bytes. Sectors= 35843670 [17501 MB]
> [17.5 GB]
> sde:
> sde1
>
> [snipped]
>
> (read) sdb1's sb offset: 17920384 [events: 00000085]
> (read) sdc1's sb offset: 17920384 [events: 00000085]
> (read) sdd1's sb offset: 17920384 [events: 00000085]
> (read) sde1's sb offset: 17920384 [events: 00000085]
> autorun ...
> considering sde1 ...
> adding sde1 ...
> adding sdd1 ...
> adding sdc1 ...
> adding sdb1 ...
> created md0
> bind<sdb1,1>
> bind<sdc1,2>
> bind<sdd1,3>
> bind<sde1,4>
> running: <sde1><sdd1><sdc1><sdb1>
> now!
> sde1's event counter: 00000085
> sdd1's event counter: 00000085
> sdc1's event counter: 00000085
> sdb1's event counter: 00000085
> raid0 personality registered
> md0: max total readahead window set to 2048k
> md0: 4 data-disks, max readahead per data-disk: 512k
> raid0: looking at sdb1
> raid0: comparing sdb1(17920384) with sdb1(17920384)
> raid0: END
> raid0: ==> UNIQUE
> raid0: 1 zones
> raid0: looking at sdc1
> raid0: comparing sdc1(17920384) with sdb1(17920384)
> raid0: EQUAL
> raid0: looking at sdd1
> raid0: comparing sdd1(17920384) with sdb1(17920384)
> raid0: EQUAL
> raid0: looking at sde1
> raid0: comparing sde1(17920384) with sdb1(17920384)
> raid0: EQUAL
> raid0: FINAL 1 zones
> zone 0
> checking sdb1 ... contained as device 0
> (17920384) is smallest!.
> checking sdc1 ... contained as device 1
> checking sdd1 ... contained as device 2
> checking sde1 ... contained as device 3
> zone->nb_dev: 4, size: 71681536
> current zone offset: 17920384
> done.
> raid0 : md_size is 71681536 blocks.
> raid0 : conf->smallest->size is 71681536 blocks.
> raid0 : nb_zone is 1.
> raid0 : Allocating 8 bytes for hash.
> md: updating md0 RAID superblock on device
> sde1 [events: 00000086](write) sde1's sb offset: 17920384
> sdd1 [events: 00000086](write) sdd1's sb offset: 17920384
> sdc1 [events: 00000086](write) sdc1's sb offset: 17920384
> sdb1 [events: 00000086](write) sdb1's sb offset: 17920384
> .
> ... autorun DONE.
> Detected scsi tape st0 at scsi0, channel 0, id 5, lun 0
> st: bufsize 32768, wrt 30720, max init. buffers 4, s/g segs
> 16.
>
>
> These are the outputs of bonnie++ version 1.00 compiled on 2.2.14
> kernel ( redhat 6.2)
>
>
> kernel 2.2.14 no tagged
> Version 1.00 ------Sequential Output------ --Sequential Input-
> --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> Machine MB K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
> /sec %CP
> Unknown 1000 8400 97 56908 70 21380 48 8475 96 58199
> 44 nan -21474836
> 48
> ------Sequential Create------ --------Random
> Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read---
> -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> /sec %CP
> 30 175 96 627 99 6451 99 182 99 806
> 99 722 91
> Unknown,1000,8400,97,56908,70,21380,48,8475,96,58199,44,
> nan,-2147483648,30,175,96,62
> 7,99,6451,99,182,99,806,99,722,91
>
> kernel 2.4.0-test4 no tagged
> Version 1.00 ------Sequential Output------ --Sequential Input-
> --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> Machine MB K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
> /sec %CP
> Unknown 1000 8249 97 51642 37 10498 18 6190 72 17248
> 19 nan -2147483648
> ------Sequential Create------ --------Random
> Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read---
> -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> /sec %CP
> 30 174 99 +++++ 93 9417 93 180 99 +++++ 104
> 1282 98
> Unknown,1000,8249,97,51642,37,10498,18,6190,72,17248,19,
> nan,-2147483648,30,174,99,+++++,93,9417,93,180,99,+++++,104,1282,98
>
>
> What about them? In particular the big difference between rewrite seq.
> output (21380 48 % cpu in 2.2 vs 10498 18%
> in 2.4) and block seq. input (58199 44% in 2.2 vs 17248 19% in
> 2.4)?
>
> Making dd or cp of big files the performances of 2.4 remains 1/3
> respect of 2.2.14 (due to seq. input bad performance??),
> eg. 62 secs for 512MB dd with 1MB block size versus 23 secs in
> 2.2.14). The cpu load is 45% in 2.2 versus 18% in 2.4.
> The problem with kswapd overload seems not to be so present analyzing
> vmstat, but the
> performance gap remains.
> Is philosophical (logical) change toward multi user/multi processor
> environment or bad performance?
> Thanks in advance for your clarifications.
> Gianluca
>
>
> PS: tell me if I can be of any help for testing conditions with my
> hardware.

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