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Tue, 21 Apr 2026 15:51:04 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 21 Apr 2026 15:51:02 -0700 Message-Id: To: "Harry Yoo (Oracle)" , "Andrew Morton" , "Vlastimil Babka" Cc: "Christoph Lameter" , "David Rientjes" , "Roman Gushchin" , "Hao Li" , "Alexei Starovoitov" , "Uladzislau Rezki" , "Paul E . McKenney" , "Frederic Weisbecker" , "Neeraj Upadhyay" , "Joel Fernandes" , "Josh Triplett" , "Boqun Feng" , "Zqiang" , "Steven Rostedt" , "Mathieu Desnoyers" , "Lai Jiangshan" , , Subject: Re: [PATCH 7/8] mm/slab: introduce deferred submission of rcu sheaves From: "Alexei Starovoitov" X-Mailer: aerc References: <20260416091022.36823-1-harry@kernel.org> <20260416091022.36823-8-harry@kernel.org> In-Reply-To: <20260416091022.36823-8-harry@kernel.org> X-Stat-Signature: mepugbtg3j5mekcu5fs443ikdh6etrqq X-Rspamd-Queue-Id: CE9BCA000A X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776811865-824327 X-HE-Meta: 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 DSqB1zYm 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu Apr 16, 2026 at 2:10 AM PDT, Harry Yoo (Oracle) wrote: > Instead of falling back when the rcu sheaf becomes full, implement > deferred submission of rcu sheaves. If kfree_rcu_sheaf() is invoked > by kfree_rcu_nolock() (!allow_spin) and IRQs are disabled, the CPU might > be in the middle of call_rcu() and thus defer call_rcu() with irq_work. > > Submit all deferred RCU sheaves to call_rcu() before calling > rcu_barrier() to ensure the promise of kvfree_rcu_barrier(). > > An alternative approach could be to implement this in the RCU subsystem, > tracking if it's safe to call call_rcu() and allowing falling back to > deferred call_rcu() at the cost of more expensive rcu_barrier() calls. Yeah. call_rcu_nolock() will be really handy here and in other places. When you respin pls pick some tree that sashiko knows about. So it can apply it all and review it all. Currently it reviewed only patch 1 and failed to apply the most interesting= 4+ https://sashiko.dev/#/patchset/20260416091022.36823-1-harry%40kernel.org