From: Srikar Dronamraju <srikar@linux.vnet.ibm.com> To: Michael Ellerman <mpe@ellerman.id.au> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Ajay Kaher <akaher@vmware.com>, Alexey Makhalov <amakhalov@vmware.com>, Christophe Leroy <christophe.leroy@csgroup.eu>, Juergen Gross <jgross@suse.com>, linux-kernel@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>, virtualization@lists.linux-foundation.org Subject: [PATCH] powerpc/paravirt: Improve vcpu_is_preempted Date: Mon, 9 Oct 2023 10:47:40 +0530 [thread overview] Message-ID: <20231009051740.17683-1-srikar@linux.vnet.ibm.com> (raw) PowerVM Hypervisor dispatches on a whole core basis. In a shared LPAR, a CPU from a core that is preempted may have a larger latency. In such a scenario, its preferable to choose a different CPU to run. If one of the CPUs in the core is active, i.e neither CEDED nor preempted, then consider this CPU as not preempted. Also if any of the CPUs in the core has yielded but OS has not requested CEDE or CONFER, then consider this CPU to be preempted. Cc: Ajay Kaher <akaher@vmware.com> Cc: Alexey Makhalov <amakhalov@vmware.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Juergen Gross <jgross@suse.com> Cc: linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: virtualization@lists.linux-foundation.org Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> --- arch/powerpc/include/asm/paravirt.h | 33 ++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h index e08513d73119..a980756f58df 100644 --- a/arch/powerpc/include/asm/paravirt.h +++ b/arch/powerpc/include/asm/paravirt.h @@ -121,9 +121,19 @@ static inline bool vcpu_is_preempted(int cpu) if (!is_shared_processor()) return false; + if (!(yield_count_of(cpu) & 1)) + return false; + + /* + * If CPU has yielded but OS has not requested idle then this CPU is + * definitely preempted. + */ + if (!lppaca_of(cpu).idle) + return true; + #ifdef CONFIG_PPC_SPLPAR if (!is_kvm_guest()) { - int first_cpu; + int first_cpu, i; /* * The result of vcpu_is_preempted() is used in a @@ -149,11 +159,28 @@ static inline bool vcpu_is_preempted(int cpu) */ if (cpu_first_thread_sibling(cpu) == first_cpu) return false; + + /* + * If any of the threads of this core is not preempted or + * ceded, then consider this CPU to be non-preempted + */ + first_cpu = cpu_first_thread_sibling(cpu); + for (i = first_cpu; i < first_cpu + threads_per_core; i++) { + if (i == cpu) + continue; + if (!(yield_count_of(i) & 1)) + return false; + if (!lppaca_of(i).idle) + return true; + } } #endif - if (yield_count_of(cpu) & 1) - return true; + /* + * None of the threads in this thread group are running but none of + * them were preempted too. Hence assume the thread to be + * non-preempted. + */ return false; } -- 2.31.1
WARNING: multiple messages have this Message-ID (diff)
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com> To: Michael Ellerman <mpe@ellerman.id.au> Cc: Juergen Gross <jgross@suse.com>, Srikar Dronamraju <srikar@linux.vnet.ibm.com>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ajay Kaher <akaher@vmware.com>, Nicholas Piggin <npiggin@gmail.com>, Alexey Makhalov <amakhalov@vmware.com>, linuxppc-dev <linuxppc-dev@lists.ozlabs.org> Subject: [PATCH] powerpc/paravirt: Improve vcpu_is_preempted Date: Mon, 9 Oct 2023 10:47:40 +0530 [thread overview] Message-ID: <20231009051740.17683-1-srikar@linux.vnet.ibm.com> (raw) PowerVM Hypervisor dispatches on a whole core basis. In a shared LPAR, a CPU from a core that is preempted may have a larger latency. In such a scenario, its preferable to choose a different CPU to run. If one of the CPUs in the core is active, i.e neither CEDED nor preempted, then consider this CPU as not preempted. Also if any of the CPUs in the core has yielded but OS has not requested CEDE or CONFER, then consider this CPU to be preempted. Cc: Ajay Kaher <akaher@vmware.com> Cc: Alexey Makhalov <amakhalov@vmware.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Juergen Gross <jgross@suse.com> Cc: linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: virtualization@lists.linux-foundation.org Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> --- arch/powerpc/include/asm/paravirt.h | 33 ++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h index e08513d73119..a980756f58df 100644 --- a/arch/powerpc/include/asm/paravirt.h +++ b/arch/powerpc/include/asm/paravirt.h @@ -121,9 +121,19 @@ static inline bool vcpu_is_preempted(int cpu) if (!is_shared_processor()) return false; + if (!(yield_count_of(cpu) & 1)) + return false; + + /* + * If CPU has yielded but OS has not requested idle then this CPU is + * definitely preempted. + */ + if (!lppaca_of(cpu).idle) + return true; + #ifdef CONFIG_PPC_SPLPAR if (!is_kvm_guest()) { - int first_cpu; + int first_cpu, i; /* * The result of vcpu_is_preempted() is used in a @@ -149,11 +159,28 @@ static inline bool vcpu_is_preempted(int cpu) */ if (cpu_first_thread_sibling(cpu) == first_cpu) return false; + + /* + * If any of the threads of this core is not preempted or + * ceded, then consider this CPU to be non-preempted + */ + first_cpu = cpu_first_thread_sibling(cpu); + for (i = first_cpu; i < first_cpu + threads_per_core; i++) { + if (i == cpu) + continue; + if (!(yield_count_of(i) & 1)) + return false; + if (!lppaca_of(i).idle) + return true; + } } #endif - if (yield_count_of(cpu) & 1) - return true; + /* + * None of the threads in this thread group are running but none of + * them were preempted too. Hence assume the thread to be + * non-preempted. + */ return false; } -- 2.31.1
next reply other threads:[~2023-10-09 5:18 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-10-09 5:17 Srikar Dronamraju [this message] 2023-10-09 5:17 ` [PATCH] powerpc/paravirt: Improve vcpu_is_preempted Srikar Dronamraju 2023-10-09 8:40 ` kernel test robot 2023-10-10 15:42 ` kernel test robot 2023-10-11 9:03 ` Shrikanth Hegde 2023-10-11 9:03 ` Shrikanth Hegde 2023-10-11 12:16 ` Srikar Dronamraju 2023-10-11 12:16 ` Srikar Dronamraju 2023-10-17 12:18 ` Aboorva Devarajan 2023-10-17 12:18 ` Aboorva Devarajan
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20231009051740.17683-1-srikar@linux.vnet.ibm.com \ --to=srikar@linux.vnet.ibm.com \ --cc=akaher@vmware.com \ --cc=amakhalov@vmware.com \ --cc=christophe.leroy@csgroup.eu \ --cc=jgross@suse.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linuxppc-dev@lists.ozlabs.org \ --cc=mpe@ellerman.id.au \ --cc=npiggin@gmail.com \ --cc=virtualization@lists.linux-foundation.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.