Hi
I think I have a possible explanation for your observations:
1) 1024B Block size:
> User time (seconds): 69.32
> System time (seconds): 25.15
> Percent of CPU this job got: 54%
> Elapsed (wall clock) time (h:mm:ss or m:ss): 2:54.14
> Major (requiring I/O) page faults: 43861
2) 4096B Block size:
> User time (seconds): 68.43
> System time (seconds): 24.79
> Percent of CPU this job got: 39%
> Elapsed (wall clock) time (h:mm:ss or m:ss): 3:54.87
> Major (requiring I/O) page faults: 41944
Your application seems to have a lot of small accesses (<4k). Each time
you try to read/write a single byte, the whole disk block has to be in
the buffercache.
Now when you only have to read 1k from the disk to do this, you're
faster than when you have to read 4k.
You have to chose if you need good sequential I/O performance for large
I/O transfers where you need a large block size and good random small
I/O performance where you want to have a small block size.
Have fun
Reto
CMA wrote:
>
> Sirs,
> performing extensive tests on linux platform performance, optimized as
> database server, I got IMHO confusing results:
> in particular e2fs initialized to use 1024 block/fragment size showed
> significant I/O gains over 4096 block/fragment size, while I expected the
> opposite. I would appreciate some hints to understand this.
> The test performed was a c-isam index rebuild for a large table (more than
> 300000 tuples, over 80 megs for data and 90 megs for indexes).
> Disk configurations were just cloned (no fragmentation).
> Optimal (for the specific purpose) hdparm and bdflush tuning were applied
> and tests run in single user mode.
> This behaviour was consistent through a broad range of kernel releases (up
> to 2.2.17) and h/w configurations.
> Please find attached info and test results for a reference platform.
> BTW, similar tests running interbase 4.0 DB load showed > 4x performance
> over a fully tuned Win NT 4 config (same platform) ;-)
> Regards
>
> Dr. Eng. Mauro Tassinari
> Rome, Italy
> mtassinari@libero.it
>
> dmesg
>
> Linux version 2.2.6 (root@zap) (gcc version 2.7.2.3) #20 Tue Apr 27 15:23:25
> CDT 1999
> Detected 736483166 Hz processor.
> Console: colour VGA+ 80x25
> Calibrating delay loop... 734.00 BogoMIPS
> Memory: 127708k/130944k available (1204k kernel code, 408k reserved, 1568k
> data, 56k init)
> VFS: Diskquotas version dquot_6.4.0 initialized
> CPU: Intel 00/08 stepping 03
> Checking 386/387 coupling... OK, FPU using exception 16 error reporting.
> Checking 'hlt' instruction... OK.
> Checking for popad bug... OK.
> POSIX conformance testing by UNIFIX
> mtrr: v1.26 (19981001) Richard Gooch (rgooch@atnf.csiro.au)
> PCI: PCI BIOS revision 2.10 entry at 0xf08f0
> PCI: Using configuration type 1
> PCI: Probing PCI hardware
> Linux NET4.0 for Linux 2.2
> Based upon Swansea University Computer Society NET3.039
> NET4: Unix domain sockets 1.0 for Linux NET4.0.
> NET4: Linux TCP/IP 1.0 for NET4.0
> IP Protocols: ICMP, UDP, TCP, IGMP
> Initializing RT netlink socket
> Starting kswapd v 1.5
> Detected PS/2 Mouse Port.
> Serial driver version 4.27 with HUB-6 MANY_PORTS MULTIPORT SHARE_IRQ enabled
> ttyS00 at 0x03f8 (irq = 4) is a 16550A
> ttyS01 at 0x02f8 (irq = 3) is a 16550A
> Real Time Clock Driver v1.09
> RAM disk driver initialized: 16 RAM disks of 4096K size
> loop: registered device at major 7
> VP_IDE: IDE controller on PCI bus 00 dev 21
> VP_IDE: not 100% native mode: will probe irqs later
> ide0: BM-DMA at 0xb800-0xb807, BIOS settings: hda:DMA, hdb:pio
> ide1: BM-DMA at 0xb808-0xb80f, BIOS settings: hdc:pio, hdd:DMA
> hda: QUANTUM FIREBALLlct15 20, ATA DISK drive
> hdd: ATAPI-CD ROM-DRIVE-50MAX, ATAPI CDROM drive
> ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
> ide1 at 0x170-0x177,0x376 on irq 15
> hda: QUANTUM FIREBALLlct15 20, 19470MB w/418kB Cache, CHS=2482/255/63
> hdd: ATAPI 40X CD-ROM drive, 128kB Cache
> Uniform CDROM driver Revision: 2.54
> Floppy drive(s): fd0 is 1.44M
> FDC 0 is a post-1991 82077
> md driver 0.36.6 MAX_MD_DEV=4, MAX_REAL=8
> linear personality registered
> raid0 personality registered
> scsi : 0 hosts.
> scsi : detected total.
> Partition check:
> hda: hda1 hda2 hda3
> VFS: Mounted root (ext2 filesystem) readonly.
> Freeing unused kernel memory: 56k freed
> Adding Swap: 136516k swap-space (priority -1)
> parport0: PC-style at 0x378 [SPP,PS2,EPP]
> lp0: using parport0 (polling).
> CSLIP: code copyright 1989 Regents of the University of California
> SLIP: version 0.8.4-NET3.019-NEWTTY-MODULAR (dynamic channels, max=256).
> SLIP linefill/keepalive option.
> PPP: version 2.3.3 (demand dialling)
> PPP line discipline registered.
> es1371: version v0.11 time 23:59:18 Apr 28 1999
> es1371: found adapter at io 0xa800 irq 5
> es1371: features: joystick 0x0
> es1371: codec vendor f?v revision 9
> es1371: codec features 18bit DAC 18bit ADC
> es1371: stereo enhancement: unknown
> rtl8139.c:v1.07 5/6/99 Donald Becker
> http://cesdis.gsfc.nasa.gov/linux/drivers/rtl8139.html
> eth0: RealTek RTL8139 Fast Ethernet at 0xa400, IRQ 10, 00:60:52:0b:ce:a4.
> st: bufsize 32768, wrt 30720, max buffers 4, s/g segs 16.
> scsi : 0 hosts.
> Linux PCMCIA Card Services 3.0.9
> kernel build: 2.2.6 #20 Sat Apr 17 23:17:12 CDT 1999
> options: [pci] [cardbus]
> Intel PCIC probe: not found.
> Databook TCIC-2 PCMCIA probe: not found.
> ds: no socket drivers loaded!
>
> rc.local
>
> #!/bin/sh
> #
> # /etc/rc.d/rc.local: Local system initialization script.
> (...skipped...)
> hdparm -a16A1c1d1k1K1m16u1W1 /dev/hda
> # tune buffer cache parameters
> bdflush -0 100 -1 5000 -2 2000 -3 32 -5 12000 -d
> # start xdm daemon
> (...skipped...)
>
> test 1024 block/fragment size
>
> BCHECK C-ISAM B-tree Checker version 1.07
> Copyright (C) 1981-1989 Informix Software, Inc.
>
> C-ISAM Files: prod
>
> Checking dictionary and file sizes.
> index file node size = 1024
> current C-ISAM index node size = 1024
> Checking data file records.
> Checking indexes and key descriptions.
> (...skipped...)
> Recreating data record free list.
> Recreating index 10.
> Recreating index 9.
> Recreating index 8.
> Recreating index 7.
> Recreating index 6.
> Recreating index 5.
> Recreating index 4.
> Recreating index 3.
> Recreating index 2.
> Recreating index 1.
> 12 index node(s) used, 0 free --349724 data record(s) used, 4 free
>
> Command being timed: "bcheck -y prod"
> User time (seconds): 69.32
> System time (seconds): 25.15
> Percent of CPU this job got: 54%
> Elapsed (wall clock) time (h:mm:ss or m:ss): 2:54.14
> Average shared text size (kbytes): 0
> Average unshared data size (kbytes): 0
> Average stack size (kbytes): 0
> Average total size (kbytes): 0
> Maximum resident set size (kbytes): 0
> Average resident set size (kbytes): 0
> Major (requiring I/O) page faults: 43861
> Minor (reclaiming a frame) page faults: 207
> Voluntary context switches: 0
> Involuntary context switches: 0
> Swaps: 95
> File system inputs: 0
> File system outputs: 0
> Socket messages sent: 0
> Socket messages received: 0
> Signals delivered: 0
> Page size (bytes): 4096
> Exit status: 0
>
> test 4096 block/fragment size
>
> BCHECK C-ISAM B-tree Checker version 1.07
> Copyright (C) 1981-1989 Informix Software, Inc.
>
> C-ISAM Files: prod
>
> Checking dictionary and file sizes.
> index file node size = 1024
> current C-ISAM index node size = 1024
> Checking data file records.
> Checking indexes and key descriptions.
> (...skipped...)
> Recreating data record free list.
> Recreating index 10.
> Recreating index 9.
> Recreating index 8.
> Recreating index 7.
> Recreating index 6.
> Recreating index 5.
> Recreating index 4.
> Recreating index 3.
> Recreating index 2.
> Recreating index 1.
> 12 index node(s) used, 0 free --349724 data record(s) used, 4 free
>
> Command being timed: "bcheck -y prod"
> User time (seconds): 68.43
> System time (seconds): 24.79
> Percent of CPU this job got: 39%
> Elapsed (wall clock) time (h:mm:ss or m:ss): 3:54.87
> Average shared text size (kbytes): 0
> Average unshared data size (kbytes): 0
> Average stack size (kbytes): 0
> Average total size (kbytes): 0
> Maximum resident set size (kbytes): 0
> Average resident set size (kbytes): 0
> Major (requiring I/O) page faults: 41944
> Minor (reclaiming a frame) page faults: 239
> Voluntary context switches: 0
> Involuntary context switches: 0
> Swaps: 32
> File system inputs: 0
> File system outputs: 0
> Socket messages sent: 0
> Socket messages received: 0
> Signals delivered: 0
> Page size (bytes): 4096
> Exit status: 0
>
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