Messages in this thread | | | From | Con Kolivas <> | Subject | Re: 2.6.20-ck1 | Date | Sun, 18 Feb 2007 11:39:19 +1100 |
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Andrew Morton writes:
> On Sun, 18 Feb 2007 08:00:06 +1100 Con Kolivas <kernel@kolivas.org> 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.
Rest assured I wasn't interested in pushing this patch for mainline anyway.
-ck users can also rest assured about this patch for the following reasons:
- The usage pattern on a desktop will guarantee that this patch helps 99.9% of the time rather than hurts. Therefore, this feature is enabled by default on -ck.
- With the usage pattern on a server of any sort, it will be unknown whether this patch helps or harms. Therefore, this feature is disabled by default on -cks.
-- -ck
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