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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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