Messages in this thread |  | | From | Andries.Brouwer@cwi ... | Date | Tue, 16 Apr 2002 15:54:15 +0200 (MEST) | Subject | readahead |
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[readahead.c has badly readable comments, on a standard 80-column display: many lines have a size just slightly over 80 chars]
In the good old days we had tunable readahead. Very good, especially for special purposes.
I recall the days where I tried to get something off a bad SCSI disk, and the kernel would die in the retries trying to read a bad block, while the data I needed was not in the block but just before. Set readahead to zero and all was fine.
Yesterday evening I was playing with my sddr09 driver, reading SmartMedia cards, and found to my dismay that the kernel wants to do a 128 block readahead. Not only is that bad on a slow medium, one is waiting a noticeable time for unwanted data, but it is worse that setting the readahead no longer works.
[Indeed, it is very desirable to be able to set readahead to zero. It is also desirable to be able to set it to a small value. Today on 2.5.8 both are impossible, readahead.c insists on a minimum readahead of 16 sectors.]
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