Messages in this thread | | | Date | Mon, 20 Mar 2006 21:54:41 +0800 | From | Wu Fengguang <> | Subject | Re: [PATCH 00/23] Adaptive read-ahead V11 |
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On Sun, Mar 19, 2006 at 10:53:46AM -0500, Jon Smirl wrote: > In another thread someone made a mention that this problem may have > something to do with the pools of memory being used for sendfile. The > readahead from sendfile is going into a moderately sized pool. When > you get 100 of them going at once the other threads flush the > readahead data out of the pool before it can be used and thus trigger > the thrashing seek storm. Is this true, that sendfile data is read > ahead into a fixed sized pool? If so, the readahead algorithms would
The pages are kept in a cache pool which is made of all the free memory. E.g. the following command shows a system with 331M cache pool:
% free -m total used free shared buffers cached Mem: 488 482 5 0 7 331 -/+ buffers/cache: 142 345 Swap: 127 0 127
That would be more than enough for the stock read-ahead to handle 100 concurrent readers.
> need to reduce the sendfile window sizes to stop the pool from > thrashing.
Sure, it is the desired behavior. This patch provides exactly this feature :)
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