linux-kernel - Re: [PATCH v9 11/13] x86/resctrl: Add sysfs interface to write mbm_local_bytes

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Message-ID: <819f31d8-5fe0-908e-9861-f4ec36105cd6@intel.com>
Date:   Thu, 15 Dec 2022 10:25:37 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <corbet@....net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v9 11/13] x86/resctrl: Add sysfs interface to write
 mbm_local_bytes_config

Hi Babu,

On 12/1/2022 7:37 AM, Babu Moger wrote:
> The current event configuration for mbm_local_bytes can be changed by
> the user by writing to the configuration file
> /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config.
> 

Same comments about subject line and usage of "current".

> The event configuration settings are domain specific and will affect all
> the CPUs in the domain.
> 
> Following are the types of events supported:
> ====  ===========================================================
> Bits   Description
> ====  ===========================================================
> 6      Dirty Victims from the QOS domain to all types of memory
> 5      Reads to slow memory in the non-local NUMA domain
> 4      Reads to slow memory in the local NUMA domain
> 3      Non-temporal writes to non-local NUMA domain
> 2      Non-temporal writes to local NUMA domain
> 1      Reads to memory in the non-local NUMA domain
> 0      Reads to memory in the local NUMA domain
> ====  ===========================================================
> 
> For example:
> To change the mbm_local_bytes_config to count all the non-temporal writes
> on domain 0, the bits 2 and 3 needs to be set which is 1100b (in hex 0xc).
> Run the command.
>     $echo  0=0xc > /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config
> 
> To change the mbm_local_bytes to count only reads to local NUMA domain 1,
> the bit 0 needs to be set which 1b (in hex 0x1). Run the command.
>     $echo  1=0x1 > /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 8a22a652a6e8..6897c480ae55 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1641,6 +1641,32 @@ static ssize_t mbm_total_bytes_config_write(struct kernfs_open_file *of,
>  	return ret ?: nbytes;
>  }
>  
> +static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
> +					    char *buf, size_t nbytes,
> +					    loff_t off)
> +{
> +	struct rdt_resource *r = of->kn->parent->priv;
> +	int ret;
> +
> +	/* Valid input requires a trailing newline */
> +	if (nbytes == 0 || buf[nbytes - 1] != '\n')
> +		return -EINVAL;
> +
> +	cpus_read_lock();
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	rdt_last_cmd_clear();
> +
> +	buf[nbytes - 1] = '\0';
> +
> +	ret = mon_config_write(r, buf, QOS_L3_MBM_LOCAL_EVENT_ID);
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -1748,9 +1774,10 @@ static struct rftype res_common_files[] = {
>  	},
>  	{
>  		.name		= "mbm_local_bytes_config",
> -		.mode		= 0444,
> +		.mode		= 0644,
>  		.kf_ops		= &rdtgroup_kf_single_ops,
>  		.seq_show	= mbm_local_bytes_config_show,
> +		.write		= mbm_local_bytes_config_write,
>  	},
>  	{
>  		.name		= "cpus",
> 
> 

With the subject and changelog comments addressed:

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette