Messages in this thread | | | From | "Song Bao Hua (Barry Song)" <> | Subject | RE: [PATCH] driver core: platform: expose numa_node to users in sysfs | Date | Tue, 2 Jun 2020 04:42:42 +0000 |
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> -----Original Message----- > From: Greg KH [mailto:gregkh@linuxfoundation.org] > Sent: Tuesday, June 2, 2020 4:24 PM > To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com> > Cc: rafael@kernel.org; iommu@lists.linux-foundation.org; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Linuxarm > <linuxarm@huawei.com>; Zengtao (B) <prime.zeng@hisilicon.com>; Robin > Murphy <robin.murphy@arm.com> > Subject: Re: [PATCH] driver core: platform: expose numa_node to users in sysfs > > On Tue, Jun 02, 2020 at 03:01:39PM +1200, Barry Song wrote: > > For some platform devices like iommu, particually ARM smmu, users may > > care about the numa locality. for example, if threads and drivers run > > near iommu, they may get much better performance on dma_unmap_sg. > > For other platform devices, users may still want to know the hardware > > topology. > > > > Cc: Prime Zeng <prime.zeng@hisilicon.com> > > Cc: Robin Murphy <robin.murphy@arm.com> > > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > > --- > > drivers/base/platform.c | 26 +++++++++++++++++++++++++- > > 1 file changed, 25 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c > > index b27d0f6c18c9..7794b9a38d82 100644 > > --- a/drivers/base/platform.c > > +++ b/drivers/base/platform.c > > @@ -1062,13 +1062,37 @@ static ssize_t driver_override_show(struct > device *dev, > > } > > static DEVICE_ATTR_RW(driver_override); > > > > +static ssize_t numa_node_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + return sprintf(buf, "%d\n", dev_to_node(dev)); > > +} > > +static DEVICE_ATTR_RO(numa_node); > > + > > +static umode_t platform_dev_attrs_visible(struct kobject *kobj, struct > attribute *a, > > + int n) > > +{ > > + struct device *dev = container_of(kobj, typeof(*dev), kobj); > > + > > + if (a == &dev_attr_numa_node.attr && > > + dev_to_node(dev) == NUMA_NO_NODE) > > + return 0; > > + > > + return a->mode; > > +} > > > > static struct attribute *platform_dev_attrs[] = { > > &dev_attr_modalias.attr, > > + &dev_attr_numa_node.attr, > > &dev_attr_driver_override.attr, > > NULL, > > }; > > -ATTRIBUTE_GROUPS(platform_dev); > > + > > +static struct attribute_group platform_dev_group = { > > + .attrs = platform_dev_attrs, > > + .is_visible = platform_dev_attrs_visible, > > +}; > > +__ATTRIBUTE_GROUPS(platform_dev); > > > > static int platform_uevent(struct device *dev, struct kobj_uevent_env *env) > > { > > Platform devices are NUMA? That's crazy, and feels like a total abuse > of platform devices and drivers that really should belong on a "real" > bus.
I am not sure if it is an abuse of platform device. But smmu is a platform device, drivers/iommu/arm-smmu-v3.c is a platform driver. In a typical ARM server, there are maybe multiple SMMU devices which can support IO virtual address and page tables for other devices on PCI-like busses. Each different SMMU device might be close to different NUMA node. There is really a hardware topology.
If you have multiple CPU packages in a NUMA server, some platform devices might Belong to CPU0, some other might belong to CPU1.
-barry
> > What drivers in the kernel today have this issue? > > thanks, > > greg k-h
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