From: Peter Zijlstra <peterz@infradead.org>
To: Wangyang Guo <wangyang.guo@intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Tianyou Li <tianyou.li@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>
Subject: Re: [PATCH RESEND^2] x86/paravirt: add backoff mechanism to virt_spin_lock
Date: Wed, 13 Aug 2025 16:33:40 +0200 [thread overview]
Message-ID: <20250813143340.GN4067720@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250813005043.1528541-1-wangyang.guo@intel.com>
On Wed, Aug 13, 2025 at 08:50:43AM +0800, Wangyang Guo wrote:
> When multiple threads waiting for lock at the same time, once lock owner
> releases the lock, waiters will see lock available and all try to lock,
> which may cause an expensive CAS storm.
>
> Binary exponential backoff is introduced. As try-lock attempt increases,
> there is more likely that a larger number threads compete for the same
> lock, so increase wait time in exponential.
You shouldn't be using virt_spin_lock() to begin with. That means you've
misconfigured your guest.
We have paravirt spinlocks for a reason.
next prev parent reply other threads:[~2025-08-13 14:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-13 0:50 Wangyang Guo
2025-08-13 14:23 ` Dave Hansen
2025-08-14 1:14 ` Guo, Wangyang
2025-08-13 14:33 ` Peter Zijlstra [this message]
2025-08-14 1:26 ` Guo, Wangyang
2025-08-14 3:10 ` [????] " Li,Rongqing
2025-08-14 10:41 ` Peter Zijlstra
2025-08-15 2:47 ` Guo, Wangyang
2025-08-14 10:39 ` Peter Zijlstra
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