> -----Original Message----- > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > Sent: Friday, March 19, 2021 11:02 PM > To: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx> > Cc: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>; > tim.c.chen@xxxxxxxxxxxxxxx; catalin.marinas@xxxxxxx; will@xxxxxxxxxx; > rjw@xxxxxxxxxxxxx; vincent.guittot@xxxxxxxxxx; bp@xxxxxxxxx; > tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; lenb@xxxxxxxxxx; peterz@xxxxxxxxxxxxx; > dietmar.eggemann@xxxxxxx; rostedt@xxxxxxxxxxx; bsegall@xxxxxxxxxx; > mgorman@xxxxxxx; msys.mizuma@xxxxxxxxx; valentin.schneider@xxxxxxx; > juri.lelli@xxxxxxxxxx; mark.rutland@xxxxxxx; sudeep.holla@xxxxxxx; > aubrey.li@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; > xuwei (O) <xuwei5@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; > guodong.xu@xxxxxxxxxx; yangyicong <yangyicong@xxxxxxxxxx>; Liguozhu (Kenneth) > <liguozhu@xxxxxxxxxxxxx>; linuxarm@xxxxxxxxxxxxx; hpa@xxxxxxxxx > Subject: Re: [RFC PATCH v5 1/4] topology: Represent clusters of CPUs within > a die > > On Fri, Mar 19, 2021 at 09:36:16AM +0000, Jonathan Cameron wrote: > > On Fri, 19 Mar 2021 06:57:08 +0000 > > "Song Bao Hua (Barry Song)" <song.bao.hua@xxxxxxxxxxxxx> wrote: > > > > > > -----Original Message----- > > > > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > > > > Sent: Friday, March 19, 2021 7:35 PM > > > > To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx> > > > > Cc: tim.c.chen@xxxxxxxxxxxxxxx; catalin.marinas@xxxxxxx; > will@xxxxxxxxxx; > > > > rjw@xxxxxxxxxxxxx; vincent.guittot@xxxxxxxxxx; bp@xxxxxxxxx; > > > > tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; lenb@xxxxxxxxxx; > peterz@xxxxxxxxxxxxx; > > > > dietmar.eggemann@xxxxxxx; rostedt@xxxxxxxxxxx; bsegall@xxxxxxxxxx; > > > > mgorman@xxxxxxx; msys.mizuma@xxxxxxxxx; valentin.schneider@xxxxxxx; > Jonathan > > > > Cameron <jonathan.cameron@xxxxxxxxxx>; juri.lelli@xxxxxxxxxx; > > > > mark.rutland@xxxxxxx; sudeep.holla@xxxxxxx; aubrey.li@xxxxxxxxxxxxxxx; > > > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > > linux-acpi@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; xuwei (O) > <xuwei5@xxxxxxxxxx>; > > > > Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; guodong.xu@xxxxxxxxxx; > yangyicong > > > > <yangyicong@xxxxxxxxxx>; Liguozhu (Kenneth) <liguozhu@xxxxxxxxxxxxx>; > > > > linuxarm@xxxxxxxxxxxxx; hpa@xxxxxxxxx > > > > Subject: Re: [RFC PATCH v5 1/4] topology: Represent clusters of CPUs within > > > > a die > > > > > > > > On Fri, Mar 19, 2021 at 05:16:15PM +1300, Barry Song wrote: > > > > > diff --git a/Documentation/admin-guide/cputopology.rst > > > > b/Documentation/admin-guide/cputopology.rst > > > > > index b90dafc..f9d3745 100644 > > > > > --- a/Documentation/admin-guide/cputopology.rst > > > > > +++ b/Documentation/admin-guide/cputopology.rst > > > > > @@ -24,6 +24,12 @@ core_id: > > > > > identifier (rather than the kernel's). The actual value is > > > > > architecture and platform dependent. > > > > > > > > > > +cluster_id: > > > > > + > > > > > + the Cluster ID of cpuX. Typically it is the hardware platform's > > > > > + identifier (rather than the kernel's). The actual value is > > > > > + architecture and platform dependent. > > > > > + > > > > > book_id: > > > > > > > > > > the book ID of cpuX. Typically it is the hardware platform's > > > > > @@ -56,6 +62,14 @@ package_cpus_list: > > > > > human-readable list of CPUs sharing the same physical_package_id. > > > > > (deprecated name: "core_siblings_list") > > > > > > > > > > +cluster_cpus: > > > > > + > > > > > + internal kernel map of CPUs within the same cluster. > > > > > + > > > > > +cluster_cpus_list: > > > > > + > > > > > + human-readable list of CPUs within the same cluster. > > > > > + > > > > > die_cpus: > > > > > > > > > > internal kernel map of CPUs within the same die. > > > > > > > > Why are these sysfs files in this file, and not in a Documentation/ABI/ > > > > file which can be correctly parsed and shown to userspace? > > > > > > Well. Those ABIs have been there for much a long time. It is like: > > > > > > [root@ceph1 topology]# ls > > > core_id core_siblings core_siblings_list physical_package_id > thread_siblings thread_siblings_list > > > [root@ceph1 topology]# pwd > > > /sys/devices/system/cpu/cpu100/topology > > > [root@ceph1 topology]# cat core_siblings_list > > > 64-127 > > > [root@ceph1 topology]# > > > > > > > > > > > Any chance you can fix that up here as well? > > > > > > Yes. we will send a separate patch to address this, which won't > > > be in this patchset. This patchset will base on that one. > > > > > > > > > > > Also note that "list" is not something that goes in sysfs, sysfs is "one > > > > value per file", and a list is not "one value". How do you prevent > > > > overflowing the buffer of the sysfs file if you have a "list"? > > > > > > > > > > At a glance, the list is using "-" rather than a real list > > > [root@ceph1 topology]# cat core_siblings_list > > > 64-127 > > > > > > Anyway, I will take a look if it has any chance to overflow. > > > > It could in theory be alternate CPUs as comma separated list. > > So it's would get interesting around 500-1000 cpus (guessing). > > > > Hopefully no one has that crazy a cpu numbering scheme but it's possible > > (note that cluster is fine for this, but I guess it might eventually > > happen for core-siblings list (cpus within a package). > > > > Shouldn't crash or anything like that but might terminate early. > > We have a broken sysfs api already for listing LED numbers that has had > to be worked around in the past, please do not create a new one with > that same problem, we should learn from them :) Another place I am seeing a cpu list is in numa topology: /sys/devices/system/node/nodex/cpulist. But the code has a BUILD_BUG_ON to guard the pagebuf: static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf) { ssize_t n; cpumask_var_t mask; struct node *node_dev = to_node(dev); /* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */ BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1)); if (!alloc_cpumask_var(&mask, GFP_KERNEL)) return 0; cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask); n = cpumap_print_to_pagebuf(list, buf, mask); free_cpumask_var(mask); return n; } For lists in cpu topology, I haven't seen this while I believe we need it. Or am I missing something? > > thanks, > > greg k-h Thanks Barry
