bug#122: 23.0.60; Slowdown in directory scanning over time.

[Richard M. Stallman]

    The calls seem to be in a fairly even balance of mixture of
    Fget_buffer and Fgarbage_collect.  Why creating a list of files in a
    directory should be calling get_buffer is beyond me.

The backtrace shows why.  It is making a new code-conversion buffer.

    list-buffers
    shows about 40 buffers, and when I try switch-to-buffer with a leading
    space, there are about 200 buffers listed (about 170 of which are
    named like *code-conversion-work*<nnn>)

There must be a bug in the logic that decides whether to make a new
code-conversion buffer, so that it makes too many of them.

The code looks inefficient too.  Even when it reuses the
code-conversion buffer, it calls Fget_buffer_create.
It seems to be killing and recreating these buffers,
which must be slow.

I think it would be better to make one and never kill it.

Handa-san, under what circumstances should it need to use more than
one of these buffers?  Can character set encoding and decoding ever be
done recursively?  It seems to me that that should never happen, so
one such buffer should be enough.