From: Srikar Dronamraju <srikar@linux•vnet.ibm.com>
To: Nathan Lynch <nathanl@linux•ibm.com>
Cc: Satheesh Rajendran <sathnaga@linux•vnet.ibm.com>,
linuxppc-dev <linuxppc-dev@lists•ozlabs.org>,
Nicholas Piggin <npiggin@gmail•com>
Subject: Re: [PATCH v2 3/4] powerpc/numa: Early request for home node associativity
Date: Fri, 6 Sep 2019 09:11:10 +0530 [thread overview]
Message-ID: <20190906034110.GA12412@linux.vnet.ibm.com> (raw)
In-Reply-To: <87tv9qqzm7.fsf@linux.ibm.com>
> >
> > While here, fix a problem where of_node_put could be called even when
> > of_get_cpu_node was not successful.
>
> of_node_put() handles NULL arguments, so this should not be necessary.
>
Ok
> > @@ -875,7 +908,7 @@ void __init mem_topology_setup(void)
> > reset_numa_cpu_lookup_table();
> >
> > for_each_present_cpu(cpu)
> > - numa_setup_cpu(cpu);
> > + numa_setup_cpu(cpu, false);
> > }
>
> I'm open to other points of view here, but I would prefer two separate
> functions, something like vphn_get_nid() for runtime and
> vphn_get_nid_early() (which could be __init) for boot-time
> initialization. Propagating a somewhat unexpressive boolean flag through
> two levels of function calls in this code is unappealing...
>
Somehow not convinced that we need to duplicate function just to avoid
passing a bool.
If propagating a boolean flag in two levels of function calls is an issue,
we could decipher the logic in numa_setup_cpu itself
Something like this
static int numa_setup_cpu(unsigned long lcpu, bool get_hwid)
{
....
if (firmware_has_feature(FW_FEATURE_VPHN)) {
long hwid;
if (get_hwid)
hwid = get_hard_smp_processor_id(cpu);
else
hwid = cpu_to_phys_id[cpu];
nid = vphn_get_nid(lcpu, hwid);
}
....
Would this help?
> Regardless, I have an annoying question :-) Isn't it possible that,
> while Linux is calling vphn_get_nid() for each logical cpu in sequence,
> the platform could change a virtual processor's node assignment,
> potentially causing sibling threads to get different node assignments
> and producing an incoherent topology (which then leads to sched domain
> assertions etc)?
>
Right, its certainly possible for node assignment to change while we iterate
through the siblings. Do you have an recommendations?
> If so, I think more care is needed. The algorithm should make the vphn
> call only once per cpu node, I think?
I didn't get "once per cpu node", How do we know which all cpus are part of
that cpu node? Or did you mean once per cpu core?
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2019-09-06 3:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 5:50 [PATCH v2 0/4] Early node associativity Srikar Dronamraju
2019-08-29 5:50 ` [PATCH v2 1/4] powerpc/vphn: Check for error from hcall_vphn Srikar Dronamraju
2019-08-29 5:50 ` [PATCH v2 2/4] powerpc/numa: Handle extra hcall_vphn error cases Srikar Dronamraju
2019-08-29 5:50 ` [PATCH v2 3/4] powerpc/numa: Early request for home node associativity Srikar Dronamraju
2019-09-05 20:04 ` Nathan Lynch
2019-09-06 3:41 ` Srikar Dronamraju [this message]
2019-09-06 13:49 ` Srikar Dronamraju
2019-09-06 21:34 ` Nathan Lynch
2019-08-29 5:50 ` [PATCH v2 4/4] powerpc/numa: Remove late " Srikar Dronamraju
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190906034110.GA12412@linux.vnet.ibm.com \
--to=srikar@linux$(echo .)vnet.ibm.com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=nathanl@linux$(echo .)ibm.com \
--cc=npiggin@gmail$(echo .)com \
--cc=sathnaga@linux$(echo .)vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox