Messages in this thread | | | Date | Wed, 2 Mar 2016 09:41:29 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v5 5/5] lib/percpu-list: Add a config parameter for disabling per-cpu list |
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* Waiman Long <Waiman.Long@hpe.com> wrote:
> As there is concern that the larger pcpu_list_node structure and the > per-cpu overhead may be a waste of resource on small system. This patch > adds a config parameter CONFIG_PERCPU_LIST to disable the per-cpu list > if the kernel builder chooses to do so. With per-cpu list disabled, > all the different groups of per-cpu lists will be degenerated into > global lists for all the CPUs. > > The current default is to enable per-cpu list. A kernel builder needs > to explicitly turn it off. > > Signed-off-by: Waiman Long <Waiman.Long@hpe.com> > --- > fs/inode.c | 2 +- > include/linux/percpu-list.h | 93 ++++++++++++++++++++++++++++++++++++++++++- > lib/Kconfig | 14 ++++++ > lib/percpu-list.c | 24 +++++++++++- > 4 files changed, 130 insertions(+), 3 deletions(-)
I think this kind of #ifdef complexity and the doubling of our Kconfig and testing space is counterproductive, and I think the per CPU locking is a win on as small as dual core CPUs, and on UP CPUs the per CPU list becomes a single global list automatically.
I'm not against visible memory savings for overly clever scalability features, but this does not appear to be such a case, so:
NAKed-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
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