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SubjectRe: [PATCH] v5 RCU: the bloatwatch edition
On Tue, Jun 23, 2009 at 05:58:32AM -0700, Paul E. McKenney wrote:

> > > > This patch is a version of RCU designed for (!SMP && EMBEDDED)
> > > > provided as a proof of concept of a small-footprint RCU implementation.
> > > > In particular, the implementation of synchronize_rcu() is extremely
> > > > lightweight and high performance. It passes rcutorture testing in each
> > > > of the four relevant configurations (combinations of NO_HZ and PREEMPT)
> > > > on x86. This saves 1263 bytes compared to Classic RCU, and more than
> > > > three kilobytes compared to Hierarchical RCU (updated to 2.6.30):
> > >
> > > On FRV:
> > >
> > > CONFIG_CLASSIC_RCU=y
> > >
> > > text data bss dec hex filename
> > > 884 32 20 936 3a8 kernel/rcupdate.o
> > > 2616 184 0 2800 af0 kernel/rcuclassic.o
> > >
> > > CONFIG_TREE_RCU=y
> > >
> > > text data bss dec hex filename
> > > 884 32 20 936 3a8 kernel/rcupdate.o
> > > 4068 384 0 4452 1164 kernel/rcutree.o
> > >
> > > CONFIG_TINY_RCU=y
> > >
> > > text data bss dec hex filename
> > > 836 32 20 888 378 kernel/rcupdate.o
> > > 816 24 0 840 348 kernel/rcutiny.o
> > >
> > > On MN10300:
> > >
> > > CONFIG_CLASSIC_RCU=y
> > >
> > > text data bss dec hex filename
> > > 900 28 48 976 3d0 kernel/rcupdate.o
> > > 1777 184 0 1961 7a9 kernel/rcuclassic.o
> > >
> > > CONFIG_TREE_RCU=y
> > >
> > > text data bss dec hex filename
> > > 900 28 48 976 3d0 kernel/rcupdate.o
> > > 2733 384 0 3117 c2d kernel/rcutree.o
> > >
> > > CONFIG_PREEMPT_RCU=y
> > >
> > > text data bss dec hex filename
> > > 961 28 48 1037 40d kernel/rcupdate.o
> > > 3314 128 8 3450 d7a kernel/rcupreempt.o
> > >
> > > CONFIG_TINY_RCU=y
> > >
> > > text data bss dec hex filename
> > > 865 28 48 941 3ad kernel/rcupdate.o
> > > 500 24 0 524 20c kernel/rcutiny.o
> > >
> > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > >
> > > Acked-by: David Howells <dhowells@redhat.com
> >
> > Ok, that's more convincing than 900 bytes on x86.
>
> It used to be 900 bytes. In 2.6.30, it is 1263 bytes. ;-)
>
> That said, I agree that FRV and MN10300 savings are more impressive.
>
> > Paul, i guess this is .32 material anyway, right?
>
> I am personally OK with it being .32, as long as David Howells,
> Lennert Buytenhek, and Paul Mundt are OK with that schedule.

I like the patch, as nearly all ARM systems in the field right now are
non-SMP. Russell King (CCd) is the ARM maintainer, so he should comment
on the proposed timeline.


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