linux-kernel - Re: [PATCH] pseries/lparcfg: Add resource group monitoring

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Message-ID: <aJRQGGr0E5Z9Fqjw@linux.ibm.com>
Date: Thu, 7 Aug 2025 12:34:56 +0530
From: Srikar Dronamraju <srikar@...ux.ibm.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
        Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Naveen N Rao <naveen@...nel.org>
Subject: Re: [PATCH] pseries/lparcfg: Add resource group monitoring

* Shrikanth Hegde <sshegde@...ux.ibm.com> [2025-08-06 19:49:13]:

> 
> 
> On 8/5/25 11:13, Srikar Dronamraju wrote:
> > * Shrikanth Hegde <sshegde@...ux.ibm.com> [2025-08-01 19:27:22]:
> > 
> 
> > > 
> > > Could you please add a link to patch on power utils on how it is being consumed?
> > 
> > I am not sure I understood your query, it looks a bit ambiguous.
> > 
> > If your query is on how lparcfg data is being consumed.
> > All tools that are consuming lparcfg will continue to use the same way.
> > Since this is not changing the way lparcfg is being consumed, I think it is
> > redundant information that need not be carried in all the changes/commits to
> > lparcfg. Such an information would be required when lparcfg file was
> > created.
> 
> I was saying you could point to power utils patch that you have sent which says how
> one would consume this.
> 
> https://groups.google.com/g/powerpc-utils-devel/c/8b2Ixk8vk2w

I guess, power utils patch would need a linuxppc-dev mail reference and not
vice-versa. Since this patch would sent first and the reviewers of the power
utils patch would a need a reference to this patch.

Since this patch needs to be sent first, how do I generate a url for the
second / subsequent patch?

> 
> > 
> > If your query is on how resource group data is being consumed by users.
> 
> > > 
> > > Does MODULE_VERS need to increased?
> > 
> > All tools that are consuming lparcfg will continue to use the same way.
> > If there was some conditional changes that need to be done by the tools,
> > then we should have updated the same.
> > Hence there is not need to update MODULE_VERS.
> > 
> 
> Since there are two new fields user scripts might need change is why i was suggesting
> we might need to increase MODULE_VERS

I still dont see a reason for increasing the MODULE_VERS

> 
> > > 
> > > > @@ -78,6 +78,8 @@ struct hvcall_ppp_data {
> > > >    	u8	capped;
> > > >    	u8	weight;
> > > >    	u8	unallocated_weight;
> > > > +	u8      resource_group_index;
> > > > +	u16     active_procs_in_resource_group;
> > > >    	u16	active_procs_in_pool;
> > > >    	u16	active_system_procs;
> > > >    	u16	phys_platform_procs;
> > > > @@ -86,7 +88,7 @@ struct hvcall_ppp_data {
> > > >    };
> > > >    /*
> > > > - * H_GET_PPP hcall returns info in 4 parms.
> > > > + * H_GET_PPP hcall returns info in 5 parms.
> > > >     *  entitled_capacity,unallocated_capacity,
> > > >     *  aggregation, resource_capability).
> > > >     *
> > > > @@ -94,11 +96,11 @@ struct hvcall_ppp_data {
> > > >     *  R5 = Unallocated Processor Capacity Percentage.
> > > >     *  R6 (AABBCCDDEEFFGGHH).
> > > >     *      XXXX - reserved (0)
> > > > - *          XXXX - reserved (0)
> > > > + *          XXXX - Active Cores in Resource Group
> > > >     *              XXXX - Group Number
> > > >     *                  XXXX - Pool Number.
> > > >     *  R7 (IIJJKKLLMMNNOOPP).
> > > > - *      XX - reserved. (0)
> > > > + *      XX - Resource group Number
> > > >     *        XX - bit 0-6 reserved (0).   bit 7 is Capped indicator.
> > > >     *          XX - variable processor Capacity Weight
> > > >     *            XX - Unallocated Variable Processor Capacity Weight.
> > > > @@ -120,9 +122,11 @@ static unsigned int h_get_ppp(struct hvcall_ppp_data *ppp_data)
> > > >    	ppp_data->entitlement = retbuf[0];
> > > >    	ppp_data->unallocated_entitlement = retbuf[1];
> > > > +	ppp_data->active_procs_in_resource_group = (retbuf[2] >> 4 * 8) & 0xffff;
> > > >    	ppp_data->group_num = (retbuf[2] >> 2 * 8) & 0xffff;
> > > >    	ppp_data->pool_num = retbuf[2] & 0xffff;
> > > > +	ppp_data->resource_group_index = (retbuf[3] >> 7 *  8) & 0xff;
> > > >    	ppp_data->capped = (retbuf[3] >> 6 * 8) & 0x01;
> > > >    	ppp_data->weight = (retbuf[3] >> 5 * 8) & 0xff;
> > > >    	ppp_data->unallocated_weight = (retbuf[3] >> 4 * 8) & 0xff;
> > > > @@ -236,6 +240,13 @@ static void parse_ppp_data(struct seq_file *m)
> > > >    	seq_printf(m, "unallocated_capacity=%lld\n",
> > > >    		   ppp_data.unallocated_entitlement);
> > > > +	if (ppp_data.active_procs_in_resource_group)  {
> > > 
> > > ppp_data.active_procs_in_resource_group can ever be zero?
> > > 
> > > If the entry is absent in lparcfg, then lparstat will print it as 0 (which happens to be
> > > default RG, while default RG may have processors)
> > 
> > If active_procs_in_resource_group is 0, then we are not printing the
> > resource group information. If active_procs_in_resource_group is non-zero
> > and resource_group_index is wrong, we need to report a bug to the firmware
> > to update it. Kernel is very transparent with respect to this information.
> > It can neither verify the information received nor should we even be doing
> > this.
> > 
> > > 
> The comment was more on the necessity of if statement there.
> 
> +	if (ppp_data.active_procs_in_resource_group)  {
> 
> If one runs lparstat in the LPAR, that means ppp_data.active_procs_in_resource_group is non zero. and when
> ppp_data.active_procs_in_resource_group is zero, i don't think one can run lparstat in any of such LPAR.
> 
> btw, ppp_data.active_procs_in_resource_group can be fraction between 0,1 or is it always an integer number?
> 

ppp_data.active_procs_in_resource_group being 0 is valid, it means its running
on an hypervisor, that doesn't support Resource group.

if ppp_data.active_procs_in_resource_group is non zero and
ppp_data.resource_group_index is not present, then its a bug.

ppp_data.active_procs_in_resource_group can only be integers.

-- 
Thanks and Regards
Srikar Dronamraju