# mount -o cdp -t resctrl resctrl /sys/fs/resctrl/ # cat /sys/fs/resctrl/info/L3CODE/io_alloc disabled # cat /sys/fs/resctrl/info/L3DATA/io_alloc not supported "io_alloc" can thus be enabled for L3CODE but not for L3DATA. This is unexpected considering the feature is called "L3 Smart *Data* Cache Injection Allocation Enforcement". I understand that the interface evolved into this because the "code" allocation of CDP uses the CLOSID required by SDCIAE but I think leaking implementation details like this to the user interface can cause confusion. Since there is no distinction between code and data in these IO allocations, what do you think of connecting the io_alloc and io_alloc_cbm files within L3CODE and L3DATA so that the user can read/write from either with a read showing the same data and user able to write to either? For example, # mount -o cdp -t resctrl resctrl /sys/fs/resctrl/ # cat /sys/fs/resctrl/info/L3CODE/io_alloc disabled # cat /sys/fs/resctrl/info/L3DATA/io_alloc disabled # echo 1 > /sys/fs/resctrl/info/L3CODE/io_alloc # cat /sys/fs/resctrl/info/L3CODE/io_alloc enabled # cat /sys/fs/resctrl/info/L3DATA/io_alloc enabled # cat /sys/fs/resctrl/info/L3DATA/io_alloc_cbm 0=ffff;1=ffff # cat /sys/fs/resctrl/info/L3CODE/io_alloc_cbm 0=ffff;1=ffff # echo 1=FF > /sys/fs/resctrl/info/L3DATA/io_alloc_cbm # cat /sys/fs/resctrl/info/L3DATA/io_alloc_cbm 0=ffff;1=00ff # cat /sys/fs/resctrl/info/L3CODE/io_alloc_cbm 0=ffff;1=00ff (Note in above I removed the resource name from io_alloc_cbm to match what was discussed during previous version: https://lore.kernel.org/lkml/251c8fe1-603f-4993-a822-afb35b49cdfa@xxxxxxx/ ) What do you think? > --- > v4: The "io_alloc" interface will report "enabled/disabled/not supported" > instead of 0 or 1.. > > Updated resctrl_io_alloc_closid_get() to verify the max closid availability > using closids_supported(). > > Updated the documentation for "shareable_bits" and "bit_usage". > > NOTE: io_alloc is about specific CLOS. rdt_bit_usage_show() is not designed > handle bit_usage for specific CLOS. Its about overall system. So, we cannot > really tell the user which CLOS is shared across both hardware and software. "bit_usage" is not about CLOS but how the resource is used. Per the doc: "bit_usage": Annotated capacity bitmasks showing how all instances of the resource are used. The key here is the CBM, not CLOS. For each bit in the *CBM* "bit_usage" shows how that portion of the cache is used with the legend documented in Documentation/arch/x86/resctrl.rst. Consider a system with the following allocations: # cat /sys/fs/resctrl/schemata L3:0=0ff0 # cat /sys/fs/resctrl/info/L3/io_alloc_cbm 0=ff00 Then "bit_usage" will look like: # cat /sys/fs/resctrl/info/L3/bit_usage 0=HHHHXXXXSSSS0000 "bit_usage" shows how the cache is being used. It shows that the portion of cache represented by first four bits of CBM is unused, portion of cache represented by bits 4 to 7 of CBM is only used by software, portion of cache represented by bits 8 to 11 of CBM is shared between software and hardware, portion of cache represented by bits 12 to 15 is only used by hardware. > This is something we need to discuss. Looking at implementation in patch #5 the "io_alloc_cbm" bits of CBM are presented as software bits, since "io_alloc_cbm" represents IO from devices it should be "hardware" bits (hw_shareable), no? Reinette
