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SubjectRe: [PATCH] v5 RCU: the bloatwatch edition

* David Howells <dhowells@redhat.com> wrote:

> Paul E. McKenney <paulmck@linux.vnet.ibm.com> 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.

Paul, i guess this is .32 material anyway, right?

Since there's plenty of time, could we perhaps also do the
classic-rcu removal and integrate-rcupreempt-into-tree-rcu steps, to
reduce the (significant) config complexity perhaps?

Ingo


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