From: Helge Deller <deller@gmx.de>
To: John David Anglin <dave.anglin@bell.net>,
linux-parisc@vger.kernel.org,
James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: [PATCH][RFC] parisc: Use local tlb purges only on UP machines
Date: Sun, 25 Sep 2022 19:51:11 +0200 [thread overview]
Message-ID: <92a8b235-7d04-9931-a153-440adbc8802a@gmx.de> (raw)
In-Reply-To: <d195aae3-b76b-1365-6e53-28c6791c77e3@bell.net>
On 9/25/22 16:33, John David Anglin wrote:
> I believe this change is wrong and will reduce performance.
Yes, could be. That's why intentionally marked it RFC.
> The TLB setup for a TMPALIAS flush is local to any given CPU. So, we
> should only need a local TLB purge.
Can those function theoretially be preempted?
If so, could it be scheduled on another CPU where the TMPALIAS isn't flushed?
> A local TLB purge doesn't require locking to serialize PxTLB broadcasts. It is also faster than
> a global TLB purges
True.
> Indeed, the case that might be wrong is the one that uses pdtlb.
Which do you have in mind here?
> It potentially needs serialization
> on SMP machines. See comment in pgtable.h.
One goal of that patch was to drop the CONFIG_PA20 ifdef case,
because a 32-bit kernel could be compiled for PA8000 in which case
the "pdtlb,l" will burn the machine.
I'll send another patch which takes care of this without changing
the local purges of pdtlb on 64bit CPUs.
Helge
next prev parent reply other threads:[~2022-09-25 17:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-25 6:56 [PATCH][RFC] parisc: Use local tlb purges only on UP machines Helge Deller
2022-09-25 14:33 ` John David Anglin
2022-09-25 17:51 ` Helge Deller [this message]
2022-09-25 18:19 ` John David Anglin
2022-09-25 18:44 ` John David Anglin
2022-09-25 18:58 ` Helge Deller
2022-09-25 19:27 ` John David Anglin
2022-09-25 20:00 ` Helge Deller
2022-09-25 20:21 ` John David Anglin
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