Messages in this thread | | | Date | Wed, 11 Sep 2002 17:45:20 -0700 | From | jw schultz <> | Subject | Re: Heuristic readahead for filesystems |
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On Wed, Sep 11, 2002 at 03:21:37PM -0400, Richard B. Johnson wrote: > On Wed, 11 Sep 2002, Oliver Neukum wrote: > > Am Mittwoch, 11. September 2002 20:43 schrieb Xuan Baldauf:
> > > > Aio should be able to do it. But even that want help you with the stat > > > > data. > > > > > > Aio would help me announcing stat() usage for the future? > > > > No, it won't. But it would solve the issue of reading ahead. > > Stating needs a kernel implementation of 'stat ahead' > > - > > I think this is discussed in the future. Write-ahead is the > next problem solved. ?;)
Gating back to the original issue which was "readahead" of stat() info...
The userland open of a directory could trigger an advance reading of the directory data and of the inode structs of all it's immediate members. Almost all instances of a usermode open on a directory will be doing fstats. Even a command line ls often has options (colour, -F, etc) turned on by default that require fstat on all the entries. The question would be how far ahead of the user app would the kernel be.
I could possibly see having a fcntl() for directories to pre-read just the first block of each file to accelerate file-managers that use magic and perhaps forestall readahead pulling in more than magic will use.
-- ________________________________________________________________ J.W. Schultz Pegasystems Technologies email address: jw@pegasys.ws
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