"io_alloc" feature is a mechanism that enables direct insertion of data
from I/O devices into the L3 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.
"io_alloc" feature uses the highest CLOSID to route the traffic from I/O
devices. Provide the interface to modify io_alloc CBMs (Capacity Bit Mask)
when feature is enabled.
Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v6: Updated the user doc restctr.doc for minor texts.
Changed the subject to fs/resctrl.
v5: Changes due to FS/ARCH code restructure. The files monitor.c/rdtgroup.c
have been split between FS and ARCH directories.
Changed the code to access the CBMs via either L3CODE or L3DATA resources.
v4: Removed resctrl_io_alloc_parse_cbm and called parse_cbm() directly.
v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
and resctrl_io_alloc_closid_get().
Taken care of handling the CBM update when CDP is enabled.
Updated the commit log to make it generic.
v2: Added more generic text in documentation.
---
Documentation/filesystems/resctrl.rst | 13 ++++
fs/resctrl/ctrlmondata.c | 4 +-
fs/resctrl/internal.h | 2 +
fs/resctrl/rdtgroup.c | 89 ++++++++++++++++++++++++++-
4 files changed, 105 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index b31748ec8c61..ae1157dcb4a3 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -181,6 +181,19 @@ related to allocation:
# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
0=ffff;1=ffff
+ CBM can be configured by writing to the interface.
+
+ Example::
+
+ # echo 1=FF > /sys/fs/resctrl/info/L3/io_alloc_cbm
+ # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+ 0=ffff;1=00ff
+
+ When CDP is enabled, io_alloc directs traffic using the highest CLOSID
+ linked to an L3CODE resource. Although CBMs can be accessed through
+ either L3CODE or L3DATA resources, any updates to the schemata are
+ always routed through L3CODE.
+
Memory bandwidth(MB) subdirectory contains the following files
with respect to allocation:
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 6409637b4de6..f3e5e697945c 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -148,8 +148,8 @@ static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
* Read one cache bit mask (hex). Check that it is valid for the current
* resource type.
*/
-static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
- struct rdt_ctrl_domain *d)
+int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
+ struct rdt_ctrl_domain *d)
{
enum rdtgrp_mode mode = data->mode;
struct resctrl_staged_config *cfg;
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 10a3188ffa54..755f23934295 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -382,6 +382,8 @@ bool closid_allocated(unsigned int closid);
int resctrl_find_cleanest_closid(void);
void show_doms(struct seq_file *s, struct resctrl_schema *schema,
char *name, int closid);
+int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
+ struct rdt_ctrl_domain *d);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 0c2d2cf4baa1..f6c44fae4b72 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2037,6 +2037,92 @@ static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of,
return ret;
}
+static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
+ struct resctrl_schema *s, u32 closid)
+{
+ 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;
+ goto next;
+ }
+ }
+ return -EINVAL;
+}
+
+static 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';
+
+ if (!r->cache.io_alloc_capable) {
+ rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n");
+ return -EINVAL;
+ }
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+ rdt_staged_configs_clear();
+
+ if (!resctrl_arch_get_io_alloc_enabled(r)) {
+ rdt_last_cmd_puts("io_alloc feature is not enabled\n");
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ io_alloc_closid = resctrl_io_alloc_closid_get(r);
+ if (io_alloc_closid < 0) {
+ rdt_last_cmd_puts("Max CLOSID to support io_alloc is not available\n");
+ ret = -EINVAL;
+ goto cbm_write_out;
+ }
+
+ ret = resctrl_io_alloc_parse_line(buf, r, resctrl_schema_io_alloc(s),
+ io_alloc_closid);
+ if (ret)
+ goto cbm_write_out;
+
+ ret = resctrl_arch_update_domains(r, io_alloc_closid);
+
+cbm_write_out:
+ rdt_staged_configs_clear();
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
+
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
@@ -2198,9 +2284,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "io_alloc_cbm",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_io_alloc_cbm_show,
+ .write = resctrl_io_alloc_cbm_write,
},
{
.name = "mba_MBps_event",
--
2.34.1
Hi Babu, On 6/11/25 2:23 PM, Babu Moger wrote: > "io_alloc" feature is a mechanism that enables direct insertion of data ""io_alloc" feature is a mechanism that enables" -> ""io_alloc" feature enables" > from I/O devices into the L3 cache. By directly caching data from I/O Drop L3 > 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. > > "io_alloc" feature uses the highest CLOSID to route the traffic from I/O How is the CLOSID related here? > devices. Provide the interface to modify io_alloc CBMs (Capacity Bit Mask) > when feature is enabled. > > Signed-off-by: Babu Moger <babu.moger@amd.com> > --- ... > --- > Documentation/filesystems/resctrl.rst | 13 ++++ > fs/resctrl/ctrlmondata.c | 4 +- > fs/resctrl/internal.h | 2 + > fs/resctrl/rdtgroup.c | 89 ++++++++++++++++++++++++++- > 4 files changed, 105 insertions(+), 3 deletions(-) > > diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst > index b31748ec8c61..ae1157dcb4a3 100644 > --- a/Documentation/filesystems/resctrl.rst > +++ b/Documentation/filesystems/resctrl.rst > @@ -181,6 +181,19 @@ related to allocation: > # cat /sys/fs/resctrl/info/L3/io_alloc_cbm > 0=ffff;1=ffff > > + CBM can be configured by writing to the interface. > + > + Example:: > + > + # echo 1=FF > /sys/fs/resctrl/info/L3/io_alloc_cbm > + # cat /sys/fs/resctrl/info/L3/io_alloc_cbm > + 0=ffff;1=00ff > + > + When CDP is enabled, io_alloc directs traffic using the highest CLOSID > + linked to an L3CODE resource. Although CBMs can be accessed through > + either L3CODE or L3DATA resources, any updates to the schemata are > + always routed through L3CODE. Please do not commit resctrl to this implementation by documenting it as part of user interface. Could snippet about CDP I shared in patch 6 be placed here as a replacement? Not the usage of *may* to keep implementation options open. > + > > Memory bandwidth(MB) subdirectory contains the following files > with respect to allocation: > diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c > index 6409637b4de6..f3e5e697945c 100644 > --- a/fs/resctrl/ctrlmondata.c > +++ b/fs/resctrl/ctrlmondata.c > @@ -148,8 +148,8 @@ static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r) > * Read one cache bit mask (hex). Check that it is valid for the current > * resource type. > */ > -static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, > - struct rdt_ctrl_domain *d) > +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, > + struct rdt_ctrl_domain *d) > { > enum rdtgrp_mode mode = data->mode; > struct resctrl_staged_config *cfg; > diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h > index 10a3188ffa54..755f23934295 100644 > --- a/fs/resctrl/internal.h > +++ b/fs/resctrl/internal.h > @@ -382,6 +382,8 @@ bool closid_allocated(unsigned int closid); > int resctrl_find_cleanest_closid(void); > void show_doms(struct seq_file *s, struct resctrl_schema *schema, > char *name, int closid); > +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, > + struct rdt_ctrl_domain *d); > > #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK > int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp); > diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c > index 0c2d2cf4baa1..f6c44fae4b72 100644 > --- a/fs/resctrl/rdtgroup.c > +++ b/fs/resctrl/rdtgroup.c > @@ -2037,6 +2037,92 @@ static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, > return ret; > } > > +static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r, > + struct resctrl_schema *s, u32 closid) > +{ > + 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; > + goto next; > + } > + } > + return -EINVAL; > +} > + > +static 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'; > + > + if (!r->cache.io_alloc_capable) { > + rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n"); rdt_last_cmd_puts() requires rdtgroup_mutex to be held. > + return -EINVAL; > + } > + > + cpus_read_lock(); > + mutex_lock(&rdtgroup_mutex); > + > + rdt_last_cmd_clear(); > + rdt_staged_configs_clear(); > + > + if (!resctrl_arch_get_io_alloc_enabled(r)) { > + rdt_last_cmd_puts("io_alloc feature is not enabled\n"); > + ret = -EINVAL; > + goto cbm_write_out; can just be "out" > + } > + > + io_alloc_closid = resctrl_io_alloc_closid_get(r); > + if (io_alloc_closid < 0) { Similar to other places, since this is preceded by resctrl_arch_get_io_alloc_enabled(r) passing the io_alloc_closid has to be valid and can use proposed resctrl_io_alloc_closid() helper to simplify the code. > + rdt_last_cmd_puts("Max CLOSID to support io_alloc is not available\n"); > + ret = -EINVAL; > + goto cbm_write_out; > + } > + > + ret = resctrl_io_alloc_parse_line(buf, r, resctrl_schema_io_alloc(s), > + io_alloc_closid); Here too I think both schemata needs to be updated. > + if (ret) > + goto cbm_write_out; > + > + ret = resctrl_arch_update_domains(r, io_alloc_closid); > + > +cbm_write_out: > + rdt_staged_configs_clear(); > + mutex_unlock(&rdtgroup_mutex); > + cpus_read_unlock(); > + > + return ret ?: nbytes; > +} > + > /* rdtgroup information files for one cache resource. */ > static struct rftype res_common_files[] = { > { > @@ -2198,9 +2284,10 @@ static struct rftype res_common_files[] = { > }, > { > .name = "io_alloc_cbm", > - .mode = 0444, > + .mode = 0644, > .kf_ops = &rdtgroup_kf_single_ops, > .seq_show = resctrl_io_alloc_cbm_show, > + .write = resctrl_io_alloc_cbm_write, > }, > { > .name = "mba_MBps_event", Reinette
Hi Reinette, On 6/17/2025 11:03 PM, Reinette Chatre wrote: > Hi Babu, > > On 6/11/25 2:23 PM, Babu Moger wrote: >> "io_alloc" feature is a mechanism that enables direct insertion of data > > ""io_alloc" feature is a mechanism that enables" -> ""io_alloc" feature enables" Sure. > >> from I/O devices into the L3 cache. By directly caching data from I/O > > Drop L3 > Sure. >> 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. >> >> "io_alloc" feature uses the highest CLOSID to route the traffic from I/O > > How is the CLOSID related here? Will remove it. > >> devices. Provide the interface to modify io_alloc CBMs (Capacity Bit Mask) >> when feature is enabled. >> >> Signed-off-by: Babu Moger <babu.moger@amd.com> >> --- > > ... > >> --- >> Documentation/filesystems/resctrl.rst | 13 ++++ >> fs/resctrl/ctrlmondata.c | 4 +- >> fs/resctrl/internal.h | 2 + >> fs/resctrl/rdtgroup.c | 89 ++++++++++++++++++++++++++- >> 4 files changed, 105 insertions(+), 3 deletions(-) >> >> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst >> index b31748ec8c61..ae1157dcb4a3 100644 >> --- a/Documentation/filesystems/resctrl.rst >> +++ b/Documentation/filesystems/resctrl.rst >> @@ -181,6 +181,19 @@ related to allocation: >> # cat /sys/fs/resctrl/info/L3/io_alloc_cbm >> 0=ffff;1=ffff >> >> + CBM can be configured by writing to the interface. >> + >> + Example:: >> + >> + # echo 1=FF > /sys/fs/resctrl/info/L3/io_alloc_cbm >> + # cat /sys/fs/resctrl/info/L3/io_alloc_cbm >> + 0=ffff;1=00ff >> + >> + When CDP is enabled, io_alloc directs traffic using the highest CLOSID >> + linked to an L3CODE resource. Although CBMs can be accessed through >> + either L3CODE or L3DATA resources, any updates to the schemata are >> + always routed through L3CODE. > > Please do not commit resctrl to this implementation by documenting it as part of > user interface. Could snippet about CDP I shared in patch 6 be placed here as > a replacement? Not the usage of *may* to keep implementation options open. > Sure. Yea. Already added in show(). >> + >> >> Memory bandwidth(MB) subdirectory contains the following files >> with respect to allocation: >> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c >> index 6409637b4de6..f3e5e697945c 100644 >> --- a/fs/resctrl/ctrlmondata.c >> +++ b/fs/resctrl/ctrlmondata.c >> @@ -148,8 +148,8 @@ static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r) >> * Read one cache bit mask (hex). Check that it is valid for the current >> * resource type. >> */ >> -static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, >> - struct rdt_ctrl_domain *d) >> +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, >> + struct rdt_ctrl_domain *d) >> { >> enum rdtgrp_mode mode = data->mode; >> struct resctrl_staged_config *cfg; >> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h >> index 10a3188ffa54..755f23934295 100644 >> --- a/fs/resctrl/internal.h >> +++ b/fs/resctrl/internal.h >> @@ -382,6 +382,8 @@ bool closid_allocated(unsigned int closid); >> int resctrl_find_cleanest_closid(void); >> void show_doms(struct seq_file *s, struct resctrl_schema *schema, >> char *name, int closid); >> +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s, >> + struct rdt_ctrl_domain *d); >> >> #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK >> int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp); >> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c >> index 0c2d2cf4baa1..f6c44fae4b72 100644 >> --- a/fs/resctrl/rdtgroup.c >> +++ b/fs/resctrl/rdtgroup.c >> @@ -2037,6 +2037,92 @@ static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, >> return ret; >> } >> >> +static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r, >> + struct resctrl_schema *s, u32 closid) >> +{ >> + 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; >> + goto next; >> + } >> + } >> + return -EINVAL; >> +} >> + >> +static 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'; >> + >> + if (!r->cache.io_alloc_capable) { >> + rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n"); > > rdt_last_cmd_puts() requires rdtgroup_mutex to be held. Sure. > >> + return -EINVAL; >> + } >> + >> + cpus_read_lock(); >> + mutex_lock(&rdtgroup_mutex); >> + >> + rdt_last_cmd_clear(); >> + rdt_staged_configs_clear(); >> + >> + if (!resctrl_arch_get_io_alloc_enabled(r)) { >> + rdt_last_cmd_puts("io_alloc feature is not enabled\n"); >> + ret = -EINVAL; >> + goto cbm_write_out; > > can just be "out" Sure. > >> + } >> + >> + io_alloc_closid = resctrl_io_alloc_closid_get(r); >> + if (io_alloc_closid < 0) { > > Similar to other places, since this is preceded by resctrl_arch_get_io_alloc_enabled(r) > passing the io_alloc_closid has to be valid and can use proposed resctrl_io_alloc_closid() > helper to simplify the code. Yes. Check not required. > >> + rdt_last_cmd_puts("Max CLOSID to support io_alloc is not available\n"); >> + ret = -EINVAL; >> + goto cbm_write_out; >> + } >> + >> + ret = resctrl_io_alloc_parse_line(buf, r, resctrl_schema_io_alloc(s), >> + io_alloc_closid); > > Here too I think both schemata needs to be updated. Yes. Added it. > >> + if (ret) >> + goto cbm_write_out; >> + >> + ret = resctrl_arch_update_domains(r, io_alloc_closid); >> + >> +cbm_write_out: >> + rdt_staged_configs_clear(); >> + mutex_unlock(&rdtgroup_mutex); >> + cpus_read_unlock(); >> + >> + return ret ?: nbytes; >> +} >> + >> /* rdtgroup information files for one cache resource. */ >> static struct rftype res_common_files[] = { >> { >> @@ -2198,9 +2284,10 @@ static struct rftype res_common_files[] = { >> }, >> { >> .name = "io_alloc_cbm", >> - .mode = 0444, >> + .mode = 0644, >> .kf_ops = &rdtgroup_kf_single_ops, >> .seq_show = resctrl_io_alloc_cbm_show, >> + .write = resctrl_io_alloc_cbm_write, >> }, >> { >> .name = "mba_MBps_event", > > Reinette > Thanks Babu
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