From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH V2 2/5] ara virt interface of perf to support kvm guest os statistics collection in guest os Date: Tue, 22 Jun 2010 12:12:03 +0300 Message-ID: <4C207E63.5010504@redhat.com> References: <1277112686.2096.510.camel@ymzhang.sh.intel.com> <4C1F5452.3000107@redhat.com> <1277172510.2096.585.camel@ymzhang.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: LKML , kvm@vger.kernel.org, Ingo Molnar , Fr??d??ric Weisbecker , Arnaldo Carvalho de Melo , Cyrill Gorcunov , Lin Ming , Sheng Yang , Marcelo Tosatti , oerg Roedel , Jes Sorensen , Gleb Natapov , Zachary Amsden , zhiteng.huang@intel.com, tim.c.chen@intel.com To: "Zhang, Yanmin" Return-path: In-Reply-To: <1277172510.2096.585.camel@ymzhang.sh.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 06/22/2010 05:08 AM, Zhang, Yanmin wrote: > >> Something that is worrying is that we don't expose group information. >> perf will multiplex the events for us, but there will be a loss in accuracy. >> >> >>> #ifdef CONFIG_HAVE_HW_BREAKPOINT >>> #include >>> #endif >>> @@ -753,6 +752,20 @@ struct perf_event { >>> >>> perf_overflow_handler_t overflow_handler; >>> >>> + /* >>> + * pointers used by kvm perf paravirt interface. >>> + * >>> + * 1) Used in host kernel and points to host_perf_shadow which >>> + * has information about guest perf_event >>> + */ >>> + void *host_perf_shadow; >>> >>> >> Can we have real types instead of void pointers? >> > I just want perf generic codes have less dependency on KVM codes. > One way to do that and retain type safety is to have struct perf_client { struct perf_client_ops *ops; ... } The client (kvm) can do struct kvm_perf_client { struct perf_client pc; // kvm specific stuff }; the callbacks receive struct perf_client and use container_of to reach the kvm_perf_client that contains it. >>> + /* >>> + * 2) Used in guest kernel and points to guest_perf_shadow which >>> + * is used as a communication area with host kernel. Host kernel >>> + * copies overflow data to it when an event overflows. >>> + */ >>> + void *guest_perf_shadow; >>> >>> >> It's strange to see both guest and host parts in the same patch. >> Splitting to separate patches will really help review. >> > It's a little hard to split the patches if they change the same file. Perhaps > I could add more statements before the patch when I send it out. > With git, it's easy (once you're used to it): # go back one commit: git reset HEAD^ # selectively add bits: git add -p # commit first patch git commit -s # selectively add bits: git add -p # commit second patch git commit -s >>> @@ -1626,9 +1629,22 @@ void perf_event_task_tick(struct task_st >>> if (ctx&& ctx->nr_events&& ctx->nr_events != ctx->nr_active) >>> rotate = 1; >>> >>> - perf_ctx_adjust_freq(&cpuctx->ctx); >>> - if (ctx) >>> - perf_ctx_adjust_freq(ctx); >>> +#ifdef CONFIG_KVM_PERF >>> + if (kvm_para_available()) { >>> + /* >>> + * perf_ctx_adjust_freq causes lots of pmu->read which would >>> + * trigger too many vmexit to host kernel. We disable it >>> + * under para virt situation >>> + */ >>> + adjust_freq = 0; >>> + } >>> +#endif >>> >>> >> Perhaps we can have a batch read interface which will read many counters >> at once. >> > It's a good idea. But that will touch many perf generic codes which causes it's hard > to maintain or follow future changes. > I'm talking about the guest/host interface. So you have one vmexit and many host perf calls. -- error compiling committee.c: too many arguments to function