linux-kernel - Re: [PATCH 0/5] kfree_rcu() additions for -rcu

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Message-ID: <20190828204624.GV26530@linux.ibm.com>
Date:   Wed, 28 Aug 2019 13:46:24 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, byungchul.park@....com,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        kernel-team@...roid.com
Subject: Re: [PATCH 0/5] kfree_rcu() additions for -rcu

On Wed, Aug 28, 2019 at 04:34:58PM -0400, Joel Fernandes wrote:
> On Wed, Aug 28, 2019 at 01:28:08PM -0700, Paul E. McKenney wrote:
> > On Tue, Aug 27, 2019 at 03:01:54PM -0400, Joel Fernandes (Google) wrote:
> > > Hi,
> > > 
> > > This is a series on top of the patch "rcu/tree: Add basic support for kfree_rcu() batching".
> > > 
> > > Link: http://lore.kernel.org/r/20190814160411.58591-1-joel@joelfernandes.org
> > > 
> > > It adds performance tests, some clean ups and removal of "lazy" RCU callbacks.
> > > 
> > > Now that kfree_rcu() is handled separately from call_rcu(), we also get rid of
> > > kfree "lazy" handling from tree RCU as suggested by Paul which will be unused.
> > > This also results in a nice negative delta as well.
> > > 
> > > Joel Fernandes (Google) (5):
> > > rcu/rcuperf: Add kfree_rcu() performance Tests
> > > rcu/tree: Add multiple in-flight batches of kfree_rcu work
> > > rcu/tree: Add support for debug_objects debugging for kfree_rcu()
> > > rcu: Remove kfree_rcu() special casing and lazy handling
> > > rcu: Remove kfree_call_rcu_nobatch()
> > > 
> > > Documentation/RCU/stallwarn.txt               |  13 +-
> > > .../admin-guide/kernel-parameters.txt         |  13 ++
> > > include/linux/rcu_segcblist.h                 |   2 -
> > > include/linux/rcutiny.h                       |   5 -
> > > include/linux/rcutree.h                       |   1 -
> > > include/trace/events/rcu.h                    |  32 ++--
> > > kernel/rcu/rcu.h                              |  27 ---
> > > kernel/rcu/rcu_segcblist.c                    |  25 +--
> > > kernel/rcu/rcu_segcblist.h                    |  25 +--
> > > kernel/rcu/rcuperf.c                          | 173 +++++++++++++++++-
> > > kernel/rcu/srcutree.c                         |   4 +-
> > > kernel/rcu/tiny.c                             |  29 ++-
> > > kernel/rcu/tree.c                             | 145 ++++++++++-----
> > > kernel/rcu/tree.h                             |   1 -
> > > kernel/rcu/tree_plugin.h                      |  42 +----
> > > kernel/rcu/tree_stall.h                       |   6 +-
> > > 16 files changed, 337 insertions(+), 206 deletions(-)
> > 
> > Looks like a 131-line positive delta to me.  ;-)
> 
> Not if you overlook the rcuperf changes which is just test code. :-D ;-)

Which suggests that you should move the "nice negative delta" comment
to the commits that actually have nice negative deltas.  ;-)

							Thanx, Paul