Messages in this thread | | | Date | Mon, 15 Mar 2010 13:09:35 -0700 | From | Andrew Morton <> | Subject | Re: [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure |
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On Mon, 15 Mar 2010 13:34:50 +0100 Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com> wrote:
> c) If direct reclaim did reasonable progress in try_to_free but did not > get a page, AND there is no write in flight at all then let it try again > to free up something. > This could be extended by some kind of max retry to avoid some weird > looping cases as well. > > d) Another way might be as easy as letting congestion_wait return > immediately if there are no outstanding writes - this would keep the > behavior for cases with write and avoid the "running always in full > timeout" issue without writes.
They're pretty much equivalent and would work. But there are two things I still don't understand:
1: Why is direct reclaim calling congestion_wait() at all? If no writes are going on there's lots of clean pagecache around so reclaim should trivially succeed. What's preventing it from doing so?
2: This is, I think, new behaviour. A regression. What caused it?
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