Messages in this thread |  | | | From | KOSAKI Motohiro <> | | Subject | Re: [rfc] lru_add_drain_all() vs isolation | | Date | Wed, 9 Sep 2009 13:27:17 +0900 (JST) |
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> The usefulness of a scheme like this requires: > > 1. There are cpus that continually execute user space code > without system interaction. > > 2. There are repeated VM activities that require page isolation / > migration. > > The first page isolation activity will then clear the lru caches of the > processes doing number crunching in user space (and therefore the first > isolation will still interrupt). The second and following isolation will > then no longer interrupt the processes. > > 2. is rare. So the question is if the additional code in the LRU handling > can be justified. If lru handling is not time sensitive then yes.
Christoph, I'd like to discuss a bit related (and almost unrelated) thing. I think page migration don't need lru_add_drain_all() as synchronous, because page migration have 10 times retry.
Then asynchronous lru_add_drain_all() cause
- if system isn't under heavy pressure, retry succussfull. - if system is under heavy pressure or RT-thread work busy busy loop, retry failure.
I don't think this is problematic bahavior. Also, mlock can use asynchrounous lru drain.
What do you think?
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