Hi Tony, On 08/03/2024 18:42, Tony Luck wrote: > On Fri, Mar 08, 2024 at 06:06:45PM +0000, James Morse wrote: >> Hi guys, >> >> On 07/03/2024 23:16, Tony Luck wrote: >>> On Thu, Mar 07, 2024 at 02:39:08PM -0800, Reinette Chatre wrote: >>>> Thank you for the example. I find that significantly easier to >>>> understand than a single number in a generic "nodes_per_l3_cache". >>>> Especially with potential confusion surrounding inconsistent "nodes" >>>> between allocation and monitoring. >>>> >>>> How about domain_cpu_list and domain_cpu_map ? >> >>> Like this (my test system doesn't have SNC, so all domains are the same): >>> >>> $ cd /sys/fs/resctrl/info/ >>> $ grep . */domain* >>> L3/domain_cpu_list:0: 0-35,72-107 >>> L3/domain_cpu_list:1: 36-71,108-143 >>> L3/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff >>> L3/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000 >>> L3_MON/domain_cpu_list:0: 0-35,72-107 >>> L3_MON/domain_cpu_list:1: 36-71,108-143 >>> L3_MON/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff >>> L3_MON/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000 >>> MB/domain_cpu_list:0: 0-35,72-107 >>> MB/domain_cpu_list:1: 36-71,108-143 >>> MB/domain_cpu_map:0: 0000,00000fff,ffffff00,0000000f,ffffffff >>> MB/domain_cpu_map:1: ffff,fffff000,000000ff,fffffff0,00000000 >> >> This duplicates the information in /sys/devices/system/cpu/cpuX/cache/indexY ... is this >> really because that information is, er, wrong on SNC systems. Is it possible to fix that? > > On an SNC system the resctrl domain for L3_MON becomes the SNC node > instead of the L3 cache instance. With 2, 3, or 4 SNC nodes per L3. > > Even without the SNC issue this duplication may be a useful > convienience. On Intel to get from a resctrl domain is a multi-step > process to first find which of the indexY directories has level=3 > and then look for the "id" that matches the domain. > >> >From Tony's earlier description of how SNC changes things, the MB controls remain >> per-socket. To me it feels less invasive to fix the definition of L3 on these platforms to >> describe how it behaves (assuming that is possible), and define a new 'MB' that is NUMA >> scoped. >> This direction of redefining L3 means /sys/fs/resctrl and /sys/devices have different >> views of 'the' cache hierarchy. > > I almost went partly in that direction when I started this epic voyage. > The "almost" part was to change the names of the monitoring directories > under mon_data from (legacy non-SNC system): > > $ ls -l mon_data > total 0 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_L3_00 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_L3_01 > > to (2 socket, SNC=2 system): > > $ ls -l mon_data > total 0 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_NODE_00 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_NODE_01 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_NODE_02 > dr-xr-xr-x. 2 root root 0 Mar 8 10:31 mon_NODE_03 This would be useful for MPAM. I've seen a couple of MPAM systems that have per-NUMA MPAM controls on the 'L3', but describe it as a single global L3. The MPAM driver currently hides this by summing the NUMA node counters and reporting it as the global L3's value. > While that is in some ways a more accurate view, it breaks a lot of > legacy monitoring applications that expect the "L3" names. True - but the behaviour is different from a non SNC system, if this software can read the file - but goes wrong because the contents of the file represent something different, its still broken. Thanks, James
