Disclaimer: My current contact with Linux is limited
to reading this list and other internet sources. I
will install and try the real thing when there is
a release from one of the distributors.
D2: Swedish is my preferred language...
Quite a lot about the messages on this list are about
how to handle/optimize IO request and memory handling.
And related bugs...
There are several areas of interest:
- SCSI drivers
- SW-RAID drivers
- Huge file support (64 bit)
- Direct disk handling
- Optimal memory usage
- More threading, nice for SMP
- Media players and hold ups, due to read ahead and swap
- - - (the list goes on forever)
Could it be time for a rewrite of the device handling
middle ware? (I have some ideas)
But before starting I think a summary of file usage
patterns and device types are in order... :-)
Please feel free to add patterns, correct notation...
File usage patterns Example
-------------------------------------------
File access order patterns:
sequential access source code, multimedia during play
random access data bases, swap file
reread after close header files during compilation
File read/write patterns:
read only most system files, multimedia files
read mostly (dominant) source code
write mostly log files
write only /dev/null :-)
read/write mix swap file
File use frequency patterns:
never some yet to learn tool: vi (for me)
infrequent last projects document
frequent error sound :-(, current documents
File con currency patterns:
one thread per file application level read ahead
single thread use
multi-thread use threaded database? (find v. generate report)
multi-program use header files during parallel make
(more patterns?)
Other observations
a file may exist on several devices SW RAID
a file might be a device disc direct access!
a device might be a file encrypted disc
programs may treat all files similar tar, grep (sequential)
usage patterns varies server v. workstation
==============================================================
Device usage patterns Examples
----------------------------------------------------------
Page access order:
random access RAM disks, Flash disks
- - -
strictly sequential tape drives
IQ:
dumb and lazy CPU required to do everything (most old stuff)
simple minded one requests is handled, DMA
smart optimizes request orders, Scatter/Gather
Other observations:
speed differences like HD v. solid state HD -> different needs
inter device depend. using two EIDE devices on the same controller
physical RAM might be treated like a device!
Comments?
Regards,
Roger Larsson
Skellefteċ
Sweden
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