Re: [PATCH 1/2] Move kfree_call_rcu() to slab_common.c

[Rao Shoaib]

On 01/04/2018 12:35 PM, Rao Shoaib wrote:
> Hi Boqun,
>
> Thanks a lot for all your guidance and for catching the cut and paster 
> error. Please see inline.
>
>
> On 01/03/2018 05:38 PM, Boqun Feng wrote:
> > But you introduced a bug here, you should use rcu_state_p instead of
> > &rcu_sched_state as the third parameter for __call_rcu().
> >
> > Please re-read:
> >
> >     https://marc.info/?l=linux-mm&m=151390529209639
> >
> > , and there are other comments, which you still haven't resolved in this
> > version. You may want to write a better commit log to explain the
> > reasons of each modifcation and fix bugs or typos in your previous
> > version. That's how review process works ;-)
> >
> > Regards,
> > Boqun
> This is definitely a serious error. Thanks for catching this.
>
> As far as your previous comments are concerned, only the following one 
> has not been addressed. Can you please elaborate as I do not 
> understand the comment. The code was expanded because the new macro 
> expansion check fails. Based on Matthew Wilcox's comment I have 
> reverted rcu_head_name back to rcu_head.
It turns out I did not remember the real reason for the change. With the 
macro rewritten, using rcu_head as a macro argument does not work 
because it conflicts with the name of the type 'struct rcu_head' used in 
the macro. I have renamed the macro argument to rcu_name.

Shoaib
> > +#define kfree_rcu(ptr, rcu_head_name) \
> > +    do { \
> > +        typeof(ptr) __ptr = ptr;    \
> > +        unsigned long __off = offsetof(typeof(*(__ptr)), \
> > +                              rcu_head_name); \
> > +        struct rcu_head *__rptr = (void *)__ptr + __off; \
> > +        __kfree_rcu(__rptr, __off); \
> > +    } while (0)
>
> why do you want to open code this?
>
> Does the following text for the commit log looks better.
>
> kfree_rcu() should use the new kfree_bulk() interface for freeing rcu 
> structures
>
> The newly implemented kfree_bulk() interfaces are more efficient, 
> using the interfaces for freeing rcu structures has shown performance 
> improvements in synthetic benchmarks that allocate and free rcu 
> structures at a high rate.
>
> Shoaib
>
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