From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 255A54F8B8 for ; Thu, 11 Jan 2024 15:55:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dm5ENcQL" Received: by smtp.kernel.org (Postfix) with ESMTPS id 7649EC433F1 for ; Thu, 11 Jan 2024 15:55:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1704988508; bh=bPxy3xoGx6CkJLLwvHSmnElchYkmTUm5NhMvJ/rrBUQ=; h=From:To:Subject:Date:In-Reply-To:References:From; b=dm5ENcQLiwXbL1m0S64iPg1rulizjGP/SQZV0iXjxURbe2V5wjHiFDiOVKEYhnEKf b+zp7stlSs2C+l9R0hweVIqHfI50WQi6GlOAdOm274Pvp/2zwX1MquT78VC6ybFvDs yv4LRmYOJD3/OBATp2EdeVNOBNhM3RswU56nHoXh7jAxzlPNTaJDTEXXwNgt4QUaRu qNADdT8RrIysi6vj/i7JRQ4M+gvwv6w4RRQvFa15c/tTNSakOTs82jX5Yqrmxpp0Fk SYdedblWaymgF1TU4VizqFH1RVeOz/c6klGoBXqJ7FQTrykIn7DafvCtjB9RMPnYot +jkcB/+lJy5Lw== Received: by aws-us-west-2-korg-bugzilla-1.web.codeaurora.org (Postfix, from userid 48) id 61540C53BD3; Thu, 11 Jan 2024 15:55:08 +0000 (UTC) From: bugzilla-daemon@kernel.org To: kvm@vger.kernel.org Subject: [Bug 218259] High latency in KVM guests Date: Thu, 11 Jan 2024 15:55:08 +0000 X-Bugzilla-Reason: None X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: AssignedTo virtualization_kvm@kernel-bugs.osdl.org X-Bugzilla-Product: Virtualization X-Bugzilla-Component: kvm X-Bugzilla-Version: unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: seanjc@google.com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: virtualization_kvm@kernel-bugs.osdl.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugzilla.kernel.org/ Auto-Submitted: auto-generated Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 https://bugzilla.kernel.org/show_bug.cgi?id=3D218259 --- Comment #8 from Sean Christopherson (seanjc@google.com) --- On Mon, Dec 18, 2023, bugzilla-daemon@kernel.org wrote: > > I think the kernel is preemptible: >=20 > Ya, not fully preemptible (voluntary only), but the important part is that > KVM > will drop mmu_lock if there is contention (which is a "requirement" for t= he > bug > that Yan encountered). For posterity, the above is wrong. Volutary preemption isn't _supposed_ to enable yielding of contended spinlocks/rwlocks, but due to a bug with dynamic preemption, the behavior got enabled for all preempt models: https://lore.kernel.org/all/20240110214723.695930-1-seanjc@google.com --=20 You may reply to this email to add a comment. You are receiving this mail because: You are watching the assignee of the bug.=