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Tsirkin" To: Evanzhang Cc: qemu-devel@nongnu.org, pbonzini@redhat.com Subject: Re: [PATCH v1] rtc/mc146818rtc: improve rtc performance Message-ID: <20230925173144-mutt-send-email-mst@kernel.org> References: <4490419ebd87e46adf2294f62c5f3808d2467e40.1690188072.git.Evanzhang@archeros.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4490419ebd87e46adf2294f62c5f3808d2467e40.1690188072.git.Evanzhang@archeros.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jul 24, 2023 at 04:54:22PM +0800, Evanzhang wrote: > under heavy workloads,irq_coalesced could up to 30+, > after modification EXTERNAL_INTERRUPT reduce by 40% > > before: > Analyze events for all VMs, all VCPUs: > VM-EXIT Samples Samples% Time% > > EPT_VIOLATION 9833984 63.41% 15.96% > IO_INSTRUCTION 2160843 13.93% 50.07% > EXTERNAL_INTERRUPT 1949267 12.57% 0.89% > APIC_WRITE 767795 4.95% 0.55% > EOI_INDUCED 615308 3.97% 0.30% > HLT 130821 0.84% 31.77% > > after: > Analyze events for all VMs, all VCPUs: > VM-EXIT Samples Samples% Time% > > EPT_VIOLATION 5238031 50.91% 6.44% > IO_INSTRUCTION 2257658 21.94% 54.88% > EXTERNAL_INTERRUPT 1160086 11.28% 0.61% > APIC_WRITE 780454 7.59% 0.54% > EOI_INDUCED 615309 5.98% 0.28% > HLT 179703 1.75% 36.87% > > Signed-off-by: Evanzhang Paolo do you mind picking this old patch up? Reviewed-by: Michael S. Tsirkin > --- > hw/rtc/mc146818rtc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c > index c27c362..2995078 100644 > --- a/hw/rtc/mc146818rtc.c > +++ b/hw/rtc/mc146818rtc.c > @@ -96,8 +96,8 @@ static void rtc_coalesced_timer_update(MC146818RtcState *s) > if (s->irq_coalesced == 0) { > timer_del(s->coalesced_timer); > } else { > - /* divide each RTC interval to 2 - 8 smaller intervals */ > - int c = MIN(s->irq_coalesced, 7) + 1; > + /* divide each RTC interval to 2 - 32 smaller intervals */ > + int c = MIN(s->irq_coalesced, 31) + 1; > int64_t next_clock = qemu_clock_get_ns(rtc_clock) + > periodic_clock_to_ns(s->period / c); > timer_mod(s->coalesced_timer, next_clock); > -- > 2.9.5