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Date: Fri, 8 Mar 2024 09:13:03 -0800
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Subject: Re: [PATCH v2 00/17] x86/resctrl : Support AMD Assignable Bandwidth
 Monitoring Counters (ABMC)
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To: Peter Newman <peternewman@google.com>
CC: <babu.moger@amd.com>, James Morse <james.morse@arm.com>, <corbet@lwn.net>,
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References: <20231201005720.235639-1-babu.moger@amd.com>
 <1ae73c9a-cec4-4496-86c6-3ffcef7940d6@amd.com>
 <32a588e2-7b09-4257-b838-4268583a724d@intel.com>
 <088878bd-7533-492d-838c-6b39a93aad4d@amd.com>
 <9b20589b-6220-4ae7-bfc4-4a826b7114b1@intel.com>
 <5ddb7031-a828-4001-bfdf-5477cb85e9ed@amd.com>
 <1738493b-3248-4c9e-82a8-1599a033440d@intel.com>
 <369ab28a-f3fa-4359-8e73-4dcf214c9b6e@amd.com>
 <54687d59-d0e4-4fe7-b25f-dc1fead01ea1@intel.com>
 <11487a31-908e-d474-50c6-65617d417deb@amd.com>
 <c73f444b-83a1-4e9a-95d3-54c5165ee782@intel.com>
 <55b545fd-2851-0d0f-ac37-ec59838fb4b4@amd.com>
 <1f366890-d9ff-4ac4-9af9-1ea3128a87fc@intel.com>
 <41ca7504-c3fb-ddb6-e149-4ff82019d678@amd.com>
 <CALPaoCi=PCWr6U5zYtFPmyaFHU_iqZtZL-LaHC2mYxbETXk3ig@mail.gmail.com>
 <1d3e8b68-28fa-419b-b129-0c39df34f718@intel.com>
 <CALPaoChJPkfrMgFDhtZqwK7O8=A71CKLzQjEMG6LbgB9RhdzvA@mail.gmail.com>
 <e90ce54c-a830-4ba5-8b28-aeef06705d01@intel.com>
 <CALPaoChcJq5zoPchB2j0aM+nZpQe1xoo7w2QQUjtH+c58Yyxag@mail.gmail.com>
From: Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <CALPaoChcJq5zoPchB2j0aM+nZpQe1xoo7w2QQUjtH+c58Yyxag@mail.gmail.com>
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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@intel.com> wrote:
>> On 3/7/2024 2:33 PM, Peter Newman wrote:
>>> On Thu, Mar 7, 2024 at 12:41 PM Reinette Chatre
>>> <reinette.chatre@intel.com> 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