> -----Original Message----- > From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > Sent: Tuesday, April 21, 2015 22:28 > To: KY Srinivasan > Cc: Haiyang Zhang; devel@xxxxxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; Dexuan Cui > Subject: [PATCH 5/6] Drivers: hv: vmbus: distribute subchannels among all > vcpus > > Primary channels are distributed evenly across all vcpus we have. When the > host asks us to create subchannels it usually makes us num_cpus-1 offers Hi Vitaly, AFAIK, in the VSP of storvsc, the number of subchannel is (the_number_of_vcpus - 1) / 4. This means for a 8-vCPU guest, there is only 1 subchannel. Your new algorithm tends to make the vCPUs with small-number busier: e.g., in the 8-vCPU case, assuming we have 4 SCSI controllers: vCPU0: scsi0's PrimaryChannel (P) vCPU1: scsi0's SubChannel (S) + scsi1's P vCPU2: scsi1's S + scsi2's P vCPU3: scsi2's S + scsi3's P vCPU4: scsi3's S vCPU5, 6 and 7 are idle. In this special case, the existing algorithm is better. :-) However, I do like this idea in your patch, that is, making sure a device's primary/sub channels are assigned to differents vCPUs. I'm just wondering if we should use an even better (and complex) algorithm :-) PS, yeah, for netvsc(HV_NIC_GUID), the number of SC is indeed the_number_vcpus -1. I'm not sure about the upcoming HV_ND_GUID -- maybe it's the same as HV_NIC_GUID. Thanks, -- Dexuan > and we are supposed to distribute the work evenly among the channel > itself and all its subchannels. Make sure they are all assigned to > different vcpus. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > --- > drivers/hv/channel_mgmt.c | 29 ++++++++++++++++++++++++++++- > 1 file changed, 28 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c > index 8f2761f..daa6417 100644 > --- a/drivers/hv/channel_mgmt.c > +++ b/drivers/hv/channel_mgmt.c > @@ -270,6 +270,8 @@ static void init_vp_index(struct vmbus_channel > *channel, > int i; > bool perf_chn = false; > u32 max_cpus = num_online_cpus(); > + struct vmbus_channel *primary = channel->primary_channel, *prev; > + unsigned long flags; > > for (i = IDE; i < MAX_PERF_CHN; i++) { > if (!memcmp(type_guid->b, hp_devs[i].guid, > @@ -290,7 +292,32 @@ static void init_vp_index(struct vmbus_channel > *channel, > channel->target_vp = 0; > return; > } > - cur_cpu = (++next_vp % max_cpus); > + > + /* > + * Primary channels are distributed evenly across all vcpus we have. > + * When the host asks us to create subchannels it usually makes us > + * num_cpus-1 offers and we are supposed to distribute the work > evenly > + * among the channel itself and all its subchannels. Make sure they > are > + * all assigned to different vcpus. > + */ > + if (!primary) > + cur_cpu = (++next_vp % max_cpus); > + else { > + /* > + * Let's assign the first subchannel of a channel to the > + * primary->target_cpu+1 and all the subsequent channels > to > + * the prev->target_cpu+1. > + */ > + spin_lock_irqsave(&primary->lock, flags); > + if (primary->num_sc == 1) > + cur_cpu = (primary->target_cpu + 1) % max_cpus; > + else { > + prev = list_prev_entry(channel, sc_list); > + cur_cpu = (prev->target_cpu + 1) % max_cpus; > + } > + spin_unlock_irqrestore(&primary->lock, flags); > + } > + > channel->target_cpu = cur_cpu; > channel->target_vp = hv_context.vp_index[cur_cpu]; > } > -- > 1.9.3 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
