From: Segher Boessenkool <segher@kernel.crashing.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
Date: Fri, 31 Jan 2020 13:38:33 -0600 [thread overview]
Message-ID: <20200131193833.GF22482@gate.crashing.org> (raw)
In-Reply-To: <27cef66b-df5b-0baa-abac-5532e58bd055@c-s.fr>
On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
> Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> >On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> >>When the range is a single page, do a page flush instead.
> >
> >>+ start &= PAGE_MASK;
> >>+ end = (end - 1) | ~PAGE_MASK;
> >> if (!Hash) {
> >>- _tlbia();
> >>+ if (end - start == PAGE_SIZE)
> >>+ _tlbie(start);
> >>+ else
> >>+ _tlbia();
> >> return;
> >> }
> >
> >For just one page, you get end - start == 0 actually?
>
> Oops, good catch.
>
> Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
You have all low bits masked off in both start and end, so you get zero.
You could make the condion read "if (start == end)?
Maybe a nicer way to describe what you do is "if start and end are on the
same memory page, flush that page."
Segher
WARNING: multiple messages have this Message-ID (diff)
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page
Date: Fri, 31 Jan 2020 13:38:33 -0600 [thread overview]
Message-ID: <20200131193833.GF22482@gate.crashing.org> (raw)
In-Reply-To: <27cef66b-df5b-0baa-abac-5532e58bd055@c-s.fr>
On Fri, Jan 31, 2020 at 05:15:20PM +0100, Christophe Leroy wrote:
> Le 31/01/2020 à 16:51, Segher Boessenkool a écrit :
> >On Fri, Jan 31, 2020 at 03:37:34PM +0000, Christophe Leroy wrote:
> >>When the range is a single page, do a page flush instead.
> >
> >>+ start &= PAGE_MASK;
> >>+ end = (end - 1) | ~PAGE_MASK;
> >> if (!Hash) {
> >>- _tlbia();
> >>+ if (end - start == PAGE_SIZE)
> >>+ _tlbie(start);
> >>+ else
> >>+ _tlbia();
> >> return;
> >> }
> >
> >For just one page, you get end - start == 0 actually?
>
> Oops, good catch.
>
> Indeed you don't get PAGE_SIZE but (PAGE_SIZE - 1) for just one page.
You have all low bits masked off in both start and end, so you get zero.
You could make the condion read "if (start == end)?
Maybe a nicer way to describe what you do is "if start and end are on the
same memory page, flush that page."
Segher
next prev parent reply other threads:[~2020-01-31 19:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 15:37 [PATCH] powerpc/32s: Don't flush all TLBs when flushing one page Christophe Leroy
2020-01-31 15:37 ` Christophe Leroy
2020-01-31 15:51 ` Segher Boessenkool
2020-01-31 15:51 ` Segher Boessenkool
2020-01-31 16:15 ` Christophe Leroy
2020-01-31 16:15 ` Christophe Leroy
2020-01-31 19:38 ` Segher Boessenkool [this message]
2020-01-31 19:38 ` Segher Boessenkool
2020-02-01 7:27 ` Christophe Leroy
2020-02-01 7:27 ` Christophe Leroy
2020-02-01 14:06 ` Segher Boessenkool
2020-02-01 14:06 ` Segher Boessenkool
2020-02-01 14:53 ` Christophe Leroy
2020-02-01 14:53 ` Christophe Leroy
2020-02-01 16:17 ` Segher Boessenkool
2020-02-01 16:17 ` Segher Boessenkool
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