Re: [PATCH 0/3] i_ino uniqueness: alternate approach -- hash theinodes

From: Andrew Morton
Date: Tue Jan 23 2007 - 23:47:23 EST


On Tue, 16 Jan 2007 13:57:38 -0500
Jeff Layton <jlayton@xxxxxxxxxx> wrote:

> The questions are:
>
> 1) how much would this slow down lookups for these filesystems?
> 2) is it enough to justify adding more infrastructure to avoid it?
>
> What might be best is to start with this approach and then only move to using
> IDR or some other scheme if these extra inodes in the hashtable prove to be
> problematic.
>
> I've done some cursory testing with this patch and the overhead of hashing
> and unhashing the inodes with pipefs is pretty low -- just a few seconds of
> system time added on to the creation and destruction of 10 million pipes (very
> similar to the overhead that the IDR approach would add).

What is the additional overhead, expressed in relative terms? ie: as a percentage?
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