Messages in this thread | | | Date | Fri, 14 Feb 2003 09:36:30 +0100 | From | Helge Hafting <> | Subject | Re: How to bypass buffer caches? |
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Bruno Diniz de Paula wrote: > > Hi, > > I've sent some messages about using O_DIRECT to read files, but I > suppose that is not possible using 2.4 kernel and ext2. So I was > wondering which other alternatives I have to bypass the buffer cache of > the kernel.
You don't say why you need this. I recommend that you simply don't use a filesystem - use a partition like /dev/hda5 without a filesystem and read/write diskblocks to and from it.
Without a filesystem you decide what data goes in what disk block, and of course no fs cache gets in the way.
Transfering data between a range of blocks on a partition and a ordinary file is easy - use the dd command.
file->partition dd if=yourfile of=/dev/hdaX bs=4096 seek=<number of first block you want to use>
partition->file dd if=/dev/hdaX of=yourfile bs=4096 skip=<number of first disk block you want copied> count=<total number of blocks>
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