Hi Peter,
On 3/7/2024 3:14 PM, Peter Newman wrote:
> On Thu, Mar 7, 2024 at 2:53 PM Reinette Chatre
> <reinette.chatre@xxxxxxxxx> wrote:
>> On 3/7/2024 2:33 PM, Peter Newman wrote:
>>> On Thu, Mar 7, 2024 at 12:41 PM Reinette Chatre
>>> <reinette.chatre@xxxxxxxxx> wrote:
>>>> I understood the proposed interface appeared to focus on one use case
>>>> while the goal is to find an interface to support all requirements.
>>>> With this proposed interface it it possible to make large scale changes
>>>> with a single sysfs write.
>>>
>>> Ok I see you requested[1] one such example earlier.
>>>
>>> From what I've read, is this what you had in mind of reassigning 32
>>> counters from the first 16 groups to the next?
>>>
>>> I had found that it's hard to get a single write() syscall out of a
>>> string containing newlines, so I'm using one explicit call:
>>
>> Apologies but this is not clear to me, could you please elaborate?
>>
>> If you are referring to testing via shell you can try ANSI-C Quoting like:
>> echo -n $'c1/m1/00=_\nc2/m2/00=_\n'
>
> The echo command uses buffered output through printf() and
> putchar()[1]. The behavior of the buffering seems to be a write() call
> after each newline, causing the kernel to see the request below as 32
> individual commands.
I see different behavior. Just to confirm I added a printk() in
rdtgroup_schemata_write():
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 7471f6b747b6..00d9809a1bac 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -384,6 +384,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
rdt_staged_configs_clear();
+ printk("%s:%d Parsing %s\n", __func__, __LINE__, buf);
while ((tok = strsep(&buf, "\n")) != NULL) {
resname = strim(strsep(&tok, ":"));
if (!tok) {
I believe the behavior you are referring to is when user does something
like:
# echo -e "MB:0=90\nL3:0=7ff0" > schemata
Then, indeed it is two separate writes:
[ 636.391304] rdtgroup_schemata_write:387 Parsing MB:0=90
[ 636.397773] rdtgroup_schemata_write:387 Parsing L3:0=7ff0
When using ANSI-C Quoting I see a single write:
# echo -n $'MB:0=90\nL3:0=7ff0\n' > schemata
[ 655.879331] rdtgroup_schemata_write:387 Parsing MB:0=90
L3:0=7ff0
Reinette
