Messages in this thread | | | Date | Mon, 10 May 2004 19:39:01 -0700 | From | Andrew Morton <> | Subject | Re: 2.6.6-rc3-mm2 (4KSTACK) |
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Horst von Brand <vonbrand@inf.utfsm.cl> wrote: > > Bill Davidsen <davidsen@tmr.com> said: > > [...] > > > I tried 4k stack, I couldn't measure any improvement in anything (as in > > no visible speedup or saving in memory). > > 4K stacks lets the kernel create new threads/processes as long as there is > free memory; with 8K stacks it needs two consecutive free page frames in > physical memory, when memory is fragmented (and large) they are hard to > come by...
This is true to a surprising extent. A couple of weeks ago I observed my 256MB box freeing over 20MB of pages before it could successfully acquire a single 1-order page.
That was during an updatedb run.
And a 1-order GFP_NOFS allocation was actually livelocking, because !__GFP_FS allocations aren't allowed to enter dentry reclaim. Which is why VFS caches are now forced to use 0-order allocations.
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