Re: readahead on directories

[Phillip Susi]

On 4/20/2010 8:44 PM, Jamie Lokier wrote:
> readahead() doesn't make much sense on a directory - the offset and
> size aren't meaningful.
> 
> But does plain opendir/readdir/closedir solve the problem?

No, since those are synchronous.  I want to have readahead() queue up
reading the entire directory in the background to avoid blocking, and
get the queue filled with a bunch of requests that can be merged into
larger segments before being dispatched to the hardware.

I don't actually care to have the contents of the directories returned,
so readdir() does more than I need in that respect, and also it performs
a blocking read of one disk block at a time, which is horribly slow with
a cold cache.
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