linux-kernel - RE: [PATCH 1/1] sched/topology: Make sched_init_numa() use a set for the deduplicating sort

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Date:   Mon, 25 Jan 2021 16:45:41 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     "Song Bao Hua \(Barry Song\)" <song.bao.hua@...ilicon.com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "mingo\@kernel.org" <mingo@...nel.org>,
        "peterz\@infradead.org" <peterz@...radead.org>,
        "vincent.guittot\@linaro.org" <vincent.guittot@...aro.org>,
        "dietmar.eggemann\@arm.com" <dietmar.eggemann@....com>,
        "morten.rasmussen\@arm.com" <morten.rasmussen@....com>,
        "mgorman\@suse.de" <mgorman@...e.de>
Subject: RE: [PATCH 1/1] sched/topology: Make sched_init_numa() use a set for the deduplicating sort

On 25/01/21 09:26, Valentin Schneider wrote:
> On 25/01/21 02:23, Song Bao Hua (Barry Song) wrote:
>
>> with the below topology:
>> qemu-system-aarch64 -M virt -nographic \
>>  -smp cpus=8 \
>>  -numa node,cpus=0-1,nodeid=0 \
>>  -numa node,cpus=2-3,nodeid=1 \
>>  -numa node,cpus=4-5,nodeid=2 \
>>  -numa node,cpus=6-7,nodeid=3 \
>>  -numa dist,src=0,dst=1,val=12 \
>>  -numa dist,src=0,dst=2,val=20 \
>>  -numa dist,src=0,dst=3,val=22 \
>>  -numa dist,src=1,dst=2,val=22 \
>>  -numa dist,src=2,dst=3,val=12 \
>>  -numa dist,src=1,dst=3,val=24 \
>>
>>
>> The panic address is *1294:
>>
>>                         if (sdd->sd) {
>>     1280:       f9400e61        ldr     x1, [x19, #24]
>>     1284:       b4000201        cbz     x1, 12c4 <build_sched_domains+0x414>
>>                                 sd = *per_cpu_ptr(sdd->sd, j);
>>     1288:       93407eb7        sxtw    x23, w21
>>     128c:       aa0103e0        mov     x0, x1
>>     1290:       f8777ac2        ldr     x2, [x22, x23, lsl #3]
>>     *1294:       f8626800        ldr     x0, [x0, x2]
>>                                 if (sd && (sd->flags & SD_OVERLAP))
>>     1298:       b4000120        cbz     x0, 12bc <build_sched_domains+0x40c>
>>     129c:       b9403803        ldr     w3, [x0, #56]
>>     12a0:       365800e3        tbz     w3, #11, 12bc
>> <build_sched_domains+0x40c>
>>                                         free_sched_groups(sd->groups, 0);
>>     12a4:       f9400800        ldr     x0, [x0, #16]
>>         if (!sg)
>>
>
> Thanks for giving it a shot, let me run that with your topology and see
> where I end up.
>

I can't seem to reproduce this - your topology is actually among the ones
I tested this against.

Applying this patch obviously doesn't get rid of the group span issue, but
it does remove this warning:

[    0.354806] ERROR: Node-0 not representative
[    0.354806]
[    0.355223]   10 12 20 22
[    0.355475]   12 10 22 24
[    0.355648]   20 22 10 12
[    0.355814]   22 24 12 10

I'm running this based on tip/sched/core:

  65bcf072e20e ("sched: Use task_current() instead of 'rq->curr == p'")