Hi Reinette,
On 8/7/25 20:53, Reinette Chatre wrote:
> Hi Babu,
>
> On 8/5/25 4:30 PM, Babu Moger wrote:
>> "io_alloc" feature enables direct insertion of data from I/O devices into
>> the cache. By directly caching data from I/O devices rather than first
>> storing the I/O data in DRAM, it reduces the demands on DRAM bandwidth and
>> reduces latency to the processor consuming the I/O data.
>>
>> When CDP is enabled, io_alloc routes traffic using the highest CLOSID
>> associated with the L3CODE resource. To ensure consistent cache allocation
>> behavior, the L3CODE and L3DATA resources must remain synchronized.
>> rdtgroup_init_cat() function takes both L3CODE and L3DATA into account when
>> initializing CBMs for new groups. The io_alloc feature must maintain the
>> same behavior, ensuring that the Cache Bit Masks (CBMs) for both L3CODE and
>> L3DATA are updated together.
>
> Please rework this copy&pasted text also and make specific to what this
> patch actually does.
Sure.
>
>> Enable users to modify io_alloc CBMs (Capacity Bit Masks) via the
>> io_alloc_cbm resctrl file when io_alloc is enabled.
>
> Here the changelog can provide overview of what is done by this patch
> when a user provides a new CBM. This can include that a CBM provided
> to CDP enabled resource will copy the CBM to the CDP peer.
Sure.
>
>>
>> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
>> ---
>
>
>
>> ---
>> Documentation/filesystems/resctrl.rst | 8 +++
>> fs/resctrl/ctrlmondata.c | 97 +++++++++++++++++++++++++++
>> fs/resctrl/internal.h | 3 +
>> fs/resctrl/rdtgroup.c | 3 +-
>> 4 files changed, 110 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
>> index 3002f7fdb2fe..d955e8525af0 100644
>> --- a/Documentation/filesystems/resctrl.rst
>> +++ b/Documentation/filesystems/resctrl.rst
>> @@ -187,6 +187,14 @@ related to allocation:
>> # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
>> 0=ffff;1=ffff
>>
>> + CBMs can be configured by writing to the interface.
>> +
>> + Example::
>> +
>> + # echo 1=FF > /sys/fs/resctrl/info/L3/io_alloc_cbm
>
> It may be useful to demonstrate syntax when more than one CBM is modified.
Sure.
>
>> + # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
>> + 0=ffff;1=00ff
>> +
>> When CDP is enabled "io_alloc_cbm" associated with the DATA and CODE
>> resources may reflect the same values. For example, values read from and
>> written to /sys/fs/resctrl/info/L3DATA/io_alloc_cbm may be reflected by
>> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
>> index 641094aac322..1f69117f96f8 100644
>> --- a/fs/resctrl/ctrlmondata.c
>> +++ b/fs/resctrl/ctrlmondata.c
>> @@ -858,3 +858,100 @@ int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
>> cpus_read_unlock();
>> return ret;
>> }
>> +
>> +static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
>> + struct resctrl_schema *s, u32 closid)
>> +{
>> + enum resctrl_conf_type peer_type;
>> + struct resctrl_schema *peer_s;
>> + struct rdt_parse_data data;
>> + struct rdt_ctrl_domain *d;
>> + char *dom = NULL, *id;
>> + unsigned long dom_id;
>> +
>> +next:
>> + if (!line || line[0] == '\0')
>> + return 0;
>> +
>> + dom = strsep(&line, ";");
>> + id = strsep(&dom, "=");
>> + if (!dom || kstrtoul(id, 10, &dom_id)) {
>> + rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
>> + return -EINVAL;
>> + }
>> +
>> + dom = strim(dom);
>> + list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
>> + if (d->hdr.id == dom_id) {
>> + data.buf = dom;
>> + data.mode = RDT_MODE_SHAREABLE;
>> + data.closid = closid;
>> + if (parse_cbm(&data, s, d))
>> + return -EINVAL;
>> + /*
>> + * When CDP is enabled, update the schema for both CDP_DATA
>> + * and CDP_CODE.
>> + */
>> + if (resctrl_arch_get_cdp_enabled(r->rid)) {
>> + peer_type = resctrl_peer_type(s->conf_type);
>> + peer_s = resctrl_get_schema(peer_type);
>> + if (parse_cbm(&data, peer_s, d))
>> + return -EINVAL;
>
> CBM is still parsed twice. As I mentioned in v7 the parsing only need to be done
> once and then the resulting CBM can be copied to CDP peer.
> https://lore.kernel.org/lkml/82045638-2b26-4682-9374-1c3e400a580a@xxxxxxxxx/
My bad. Simplified now to copy the staged_config from source to its peer.
peer_type = resctrl_peer_type(s->conf_type);
memcpy(&d->staged_config[peer_type],
&d->staged_config[s->conf_type],
sizeof(*d->staged_config));
>
>> + }
>> + goto next;
>> + }
>> + }
>> +
>> + return -EINVAL;
>> +}
>> +
>> +ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
>> + size_t nbytes, loff_t off)
>> +{
>> + struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
>> + struct rdt_resource *r = s->res;
>> + u32 io_alloc_closid;
>> + int ret = 0;
>> +
>> + /* Valid input requires a trailing newline */
>> + if (nbytes == 0 || buf[nbytes - 1] != '\n')
>> + return -EINVAL;
>> +
>> + buf[nbytes - 1] = '\0';
>> +
>> + cpus_read_lock();
>> + mutex_lock(&rdtgroup_mutex);
>> +
>> + rdt_last_cmd_clear();
>> +
>> + if (!r->cache.io_alloc_capable) {
>> + rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
>> + ret = -ENODEV;
>> + goto out_unlock;
>> + }
>> +
>> + rdt_last_cmd_clear();
>
> Unnecessary rdt_last_cmd_clear().
Removed it.
>
>> + rdt_staged_configs_clear();
>
> Placement of this can be improved by putting it closer to the code that
> populates the staged configs. That is, just before resctrl_io_alloc_parse_line().
> The flow is not symmetrical in that the out_unlock exit code always
> clears the buffer whether it was used or not. I think it will be easier to
> understand if the out_unlock *only* unlocks the locks and there is a new
> goto label, for example, "out_clear_configs" that calls rdt_staged_configs_clear()
> and is used after resctrl_io_alloc_parse_line().
Yes. Sound good.
>
>> +
>> + if (!resctrl_arch_get_io_alloc_enabled(r)) {
>> + rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
>> + ret = -ENODEV;
>> + goto out_unlock;
>> + }
>> +
>> + io_alloc_closid = resctrl_io_alloc_closid(r);
>> +
>> + ret = resctrl_io_alloc_parse_line(buf, r, s, io_alloc_closid);
>> +
>> + if (ret)
>> + goto out_unlock;
>> +
>> + ret = resctrl_arch_update_domains(r, io_alloc_closid);
>> +
>> +out_unlock:
>> + rdt_staged_configs_clear();
>> + mutex_unlock(&rdtgroup_mutex);
>> + cpus_read_unlock();
>> +
>> + return ret ?: nbytes;
>> +}
>
> Reinette
>
--
Thanks
Babu Moger
