Messages in this thread | | | Subject | Re: Regression from 2.6.36 | From | Eric Dumazet <> | Date | Wed, 13 Apr 2011 04:37:36 +0200 |
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Le mardi 12 avril 2011 à 18:31 -0700, Andrew Morton a écrit : > On Wed, 13 Apr 2011 09:23:11 +0800 Changli Gao <xiaosuo@gmail.com> wrote: > > > On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton > > <akpm@linux-foundation.org> 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. > > That theory sounds less likely, but could be tested by using > alloc_pages_exact(). >
Very unlikely, since fdtable sizes are powers of two, unless you hit sysctl_nr_open and it was changed (default value being 2^20)
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