Question on sys_readahead()

Michael Marxmeier (mike@marxmeier.com)
Sat, 22 Dec 2001 00:01:31 +0100

I have a question on sys_readahead and would appreciate
some hint or a pointer.

- When was this call added?

- As far as i understand the code it reads the data into
the page cache. The data is ready sync and there is no
way to do this async and have a notification unless using
a separate thread.

A typical use i could see is preloading some data in the
page cache from a separate thread (eg. for a media player).

BTW: AFAICS the code is off by one if offset/count is not in
PAGE_SIZE chunks?

unsigned long start = offset >> PAGE_CACHE_SHIFT;
unsigned long len = (count + ((long)offset & ~PAGE_CACHE_MASK)) >> PAGE_CACHE_SHIFT;

Thanks
Michael

-- 
Michael Marxmeier           Marxmeier Software AG
E-Mail: mike@marxmeier.com  Besenbruchstrasse 9
Phone : +49 202 2431440     42285 Wuppertal, Germany
Fax   : +49 202 2431420     http://www.marxmeier.com/
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