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From: Colton Lewis <coltonlewis@google.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	andrew.jones@linux.dev, maz@kernel.org, eric.auger@redhat.com,
	oliver.upton@linux.dev, reijiw@google.com, ricarkol@google.com
Subject: Re: [kvm-unit-tests PATCH] arm: Remove MAX_SMP probe loop
Date: Tue, 20 Dec 2022 16:32:00 +0000	[thread overview]
Message-ID: <gsnt8rj2ghof.fsf@coltonlewis-kvm.c.googlers.com> (raw)
In-Reply-To: <Y6GRXreBu56PqCyG@monolith.localdoman> (message from Alexandru Elisei on Tue, 20 Dec 2022 10:41:55 +0000)

Alexandru Elisei <alexandru.elisei@arm.com> writes:

> Though I'm not sure how you managed to get MAX_SMP to go down to 6 cores  
> on
> a 12 core machine. MAX_SMP is initialized to $(getconf _NPROCESSORS_ONLN),
> so the body of the loop should never execute. I also tried it on a 6 core
> machine, and MAX_SMP was 6, not 3.

> Am I missing something?

To be clear, 12 cores was a simplified example I did not directly
verify. What happened to me was 152 cores being cut down to 4. I was
confused why one machine was running a test with 4 cores when my other
machines were running with 8 and traced it to that loop. In effect the
loop was doing MAX_SMP=floor(MAX_SMP / 2) until MAX_SMP <= 8. I printed
the iterations and MAX_SMP followed the sequence 152->76->38->19->9->4.

WARNING: multiple messages have this Message-ID (diff)
From: Colton Lewis <coltonlewis@google.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: kvm@vger.kernel.org, maz@kernel.org, andrew.jones@linux.dev,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [kvm-unit-tests PATCH] arm: Remove MAX_SMP probe loop
Date: Tue, 20 Dec 2022 16:32:00 +0000	[thread overview]
Message-ID: <gsnt8rj2ghof.fsf@coltonlewis-kvm.c.googlers.com> (raw)
In-Reply-To: <Y6GRXreBu56PqCyG@monolith.localdoman> (message from Alexandru Elisei on Tue, 20 Dec 2022 10:41:55 +0000)

Alexandru Elisei <alexandru.elisei@arm.com> writes:

> Though I'm not sure how you managed to get MAX_SMP to go down to 6 cores  
> on
> a 12 core machine. MAX_SMP is initialized to $(getconf _NPROCESSORS_ONLN),
> so the body of the loop should never execute. I also tried it on a 6 core
> machine, and MAX_SMP was 6, not 3.

> Am I missing something?

To be clear, 12 cores was a simplified example I did not directly
verify. What happened to me was 152 cores being cut down to 4. I was
confused why one machine was running a test with 4 cores when my other
machines were running with 8 and traced it to that loop. In effect the
loop was doing MAX_SMP=floor(MAX_SMP / 2) until MAX_SMP <= 8. I printed
the iterations and MAX_SMP followed the sequence 152->76->38->19->9->4.
_______________________________________________
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  reply	other threads:[~2022-12-20 16:32 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-19 18:52 [kvm-unit-tests PATCH] arm: Remove MAX_SMP probe loop Colton Lewis
2022-12-19 18:52 ` Colton Lewis
2022-12-20 10:41 ` Alexandru Elisei
2022-12-20 10:41   ` Alexandru Elisei
2022-12-20 16:32   ` Colton Lewis [this message]
2022-12-20 16:32     ` Colton Lewis
2022-12-26 18:21     ` Andrew Jones
2022-12-26 18:21       ` Andrew Jones
2023-01-05 23:09       ` Colton Lewis
2023-01-06  7:11         ` Andrew Jones
2023-01-06 17:37           ` Colton Lewis
2023-01-09  8:59             ` Andrew Jones
2023-01-09 21:43               ` Colton Lewis
2022-12-26 18:12 ` Andrew Jones
2022-12-26 18:12   ` Andrew Jones

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