Re: Regression from 2.6.36

From: Changli Gao
Date: Tue Apr 12 2011 - 21:23:38 EST

On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> It's somewhat unclear (to me) what caused this regression.
> Is it because the kernel is now doing large kmalloc()s for the fdtable,
> and this makes the page allocator go nuts trying to satisfy high-order
> page allocation requests?
> Is it because the kernel now will usually free the fdtable
> synchronously within the rcu callback, rather than deferring this to a
> workqueue?
> The latter seems unlikely, so I'm thinking this was a case of
> high-order-allocations-considered-harmful?

Maybe, but I am not sure. Maybe my patch causes too many inner
fragments. For example, when asking for 5 pages, get 8 pages, and 3
pages are wasted, then memory thrash happens finally.

Changli Gao(xiaosuo@xxxxxxxxx)
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