From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Harry Yoo (Oracle)" <harry@kernel.org>,
"Vlastimil Babka" <vbabka@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Hao Li" <hao.li@linux.dev>, "Christoph Lameter" <cl@gentwo.org>,
"David Rientjes" <rientjes@google.com>,
"Roman Gushchin" <roman.gushchin@linux.dev>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Puranjay Mohan" <puranjay@kernel.org>,
"Amery Hung" <ameryhung@gmail.com>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Clark Williams" <clrkwllms@kernel.org>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Neeraj Upadhyay" <neeraj.upadhyay@kernel.org>,
"Joel Fernandes" <joelagnelf@nvidia.com>,
"Josh Triplett" <josh@joshtriplett.org>,
"Boqun Feng" <boqun@kernel.org>,
"Uladzislau Rezki" <urezki@gmail.com>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Lai Jiangshan" <jiangshanlai@gmail.com>,
"Zqiang" <qiang.zhang@linux.dev>,
"Pedro Falcato" <pfalcato@suse.de>,
"Suren Baghdasaryan" <surenb@google.com>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
<linux-rt-devel@lists.linux.dev>, <rcu@vger.kernel.org>,
<bpf@vger.kernel.org>
Subject: Re: [PATCH for-next v3 1/9] slub_kunit: fall back to SW perf events when HW PMU is not available
Date: Mon, 15 Jun 2026 13:01:54 -0700 [thread overview]
Message-ID: <DJ9W31UCKPW5.R2LKIC72ZQ68@gmail.com> (raw)
In-Reply-To: <20260615-kfree_rcu_nolock-v3-1-70a54f3775bb@kernel.org>
On Mon Jun 15, 2026 at 4:05 AM PDT, Harry Yoo (Oracle) wrote:
> slub_kunit uses hardware perf events to invoke _nolock() APIs from NMI
> context. However, creating a HW perf event fails when there is no
> hardware PMU, or when running in a virtualized environment without a
> virtual PMU configured.
>
> Since tests are often performed in virtualized environments, fall back
> to a SW perf event so that the test can still run, even if it cannot
> cover IRQ-disabled sections.
Frankly, I wouldn't bother with this fallback, since it completely misses
irq disabled section which is the one to test with *_nolock().
VMs need to configured properly. Even nested VMs support
PERF_COUNT_HW_CPU_CYCLES.
Also in overflow_handler_test_nolock()
I would add
even->hw.interrupts = 0;
to the end to make sure it actually stress tests things.
Without it NMIs are not firing quickly enough.
next prev parent reply other threads:[~2026-06-15 20:01 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-15 11:05 [PATCH for-next v3 0/9] mm/slab: introduce kfree_rcu_nolock() and improve slub_kunit coverage Harry Yoo (Oracle)
2026-06-15 11:05 ` [PATCH for-next v3 1/9] slub_kunit: fall back to SW perf events when HW PMU is not available Harry Yoo (Oracle)
2026-06-15 11:14 ` sashiko-bot
2026-06-15 12:58 ` Harry Yoo
2026-06-15 20:01 ` Alexei Starovoitov [this message]
2026-06-15 11:05 ` [PATCH for-next v3 2/9] mm/slab, slub_kunit: register kprobe to trigger _nolock APIs Harry Yoo (Oracle)
2026-06-15 11:25 ` sashiko-bot
2026-06-15 20:04 ` Alexei Starovoitov
2026-06-15 11:05 ` [PATCH for-next v3 3/9] mm/slab: handle the !allow_spin case in kfree_rcu_sheaf() Harry Yoo (Oracle)
2026-06-15 11:24 ` sashiko-bot
2026-06-15 11:05 ` [PATCH for-next v3 4/9] mm/slab: use call_rcu() in unknown context if irqs are enabled Harry Yoo (Oracle)
2026-06-15 11:25 ` sashiko-bot
2026-06-15 11:05 ` [PATCH for-next v3 5/9] mm/slab: extend deferred free mechanism to handle rcu sheaves Harry Yoo (Oracle)
2026-06-15 11:24 ` sashiko-bot
2026-06-15 11:06 ` [PATCH for-next v3 6/9] mm/slab: allow kfree_rcu_sheaf() on PREEMPT_RT Harry Yoo (Oracle)
2026-06-15 11:19 ` sashiko-bot
2026-06-15 11:06 ` [PATCH for-next v3 7/9] mm/slab: introduce kfree_rcu_nolock() Harry Yoo (Oracle)
2026-06-15 11:22 ` sashiko-bot
2026-06-15 11:06 ` [PATCH for-next v3 8/9] mm/slab: introduce struct kfree_rcu_head and use in kfree_rcu_nolock() Harry Yoo (Oracle)
2026-06-15 11:22 ` sashiko-bot
2026-06-15 11:06 ` [PATCH for-next v3 9/9] slub_kunit: extend the test for kfree_rcu_nolock() Harry Yoo (Oracle)
2026-06-15 11:43 ` [PATCH for-next v3 0/9] mm/slab: introduce kfree_rcu_nolock() and improve slub_kunit coverage Harry Yoo
2026-06-15 20:28 ` Alexei Starovoitov
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