On Sun, 18 Feb 2007 08:00:06 +1100 Con Kolivas <kernel@xxxxxxxxxxx> wrote:
On Sunday 18 February 2007 05:45, Chuck Ebbert wrote:
...
> But the one I like, mm-filesize_dependant_lru_cache_add.patch,
> has an on-off switch.
>
...
Do you still want this patch for mainline?...
Don't think so. The problems I see are:
- It's a system-wide knob. In many situations this will do the wrong
thing. Controlling pagecache should be per-process.
- Its heuristics for working out when to invalidate the pagecache will be
too much for some situations and too little for others.
- Whatever we do, there will be some applications in some situations
which are hurt badly by changes like this: they'll do heaps of extra IO.
Generally, the penalties for getting this stuff wrong are very very high:
orders of magnitude slowdowns in the right situations. Which I suspect
will make any system-wide knob ultimately unsuccessful.