From: David Woodhouse <dwmw2@infradead.org>
To: Richard Weinberger <richard.weinberger@gmail.com>, nkela@cisco.com
Cc: "linux-mtd @ lists . infradead . org"
<linux-mtd@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
xe-linux-external@cisco.com
Subject: Re: [PATCH] jffs2: implement mount option to configure endianness
Date: Thu, 08 Nov 2018 09:11:54 +0100 [thread overview]
Message-ID: <01b82f6eb37b674effc6c8b0fa4a014deb401a85.camel@infradead.org> (raw)
In-Reply-To: <CAFLxGvz8QgK1P6d-_biSRk4fyYEobio315_tUP+cRXTvt+m1hA@mail.gmail.com>
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On Wed, 2018-11-07 at 19:14 +0100, Richard Weinberger wrote:
> On Wed, Nov 7, 2018 at 7:05 PM Nikunj Kela (nkela) <nkela@cisco.com> wrote:
> > I had tried to use configs to start with via the following patch however I was advised to have a mount option:
> > http://lists.infradead.org/pipermail/linux-mtd/2018-November/085126.html
>
> Just show performance numbers on how your implementation has an impact or not.
> So far your implementation is also not much optimized, maybe likely()
> or static keys can help...
Using likely() for the native case might help. Static keys might help a
little more, but could only work if every file system has the *same*
endianness. Unless we end up with three variants, for native vs. swap
vs. runtime checking.
We also lose a bunch of the optimisations that we gained from using
__builtin_swab functions, which let the compiler see what was going on.
But we can hypothesise and handwave about it until the cows come home;
I'd like to see a real test of whether it actually makes a difference
that we care about.
If it does, one option might be to just build separate versions of
scan.c for each endianness, since that's the critical path we care
about.
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next prev parent reply other threads:[~2018-11-08 8:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 21:49 [PATCH] jffs2: implement mount option to configure endianness Nikunj Kela
2018-11-07 9:05 ` David Woodhouse
2018-11-07 9:16 ` Joakim Tjernlund
2018-11-07 16:12 ` David Woodhouse
2018-11-07 17:33 ` Daniel Walker
2018-11-07 17:58 ` David Woodhouse
2018-11-07 18:41 ` Joakim Tjernlund
2018-11-08 15:25 ` Christoph Hellwig
2018-11-07 19:21 ` Daniel Walker
2018-11-07 18:04 ` Nikunj Kela (nkela)
2018-11-07 18:14 ` Richard Weinberger
2018-11-08 8:11 ` David Woodhouse [this message]
2018-11-08 18:01 ` Nikunj Kela (nkela)
2018-11-08 18:50 ` Joakim Tjernlund
2018-11-08 19:47 ` David Woodhouse
2018-11-12 21:43 ` Daniel Walker
2018-11-12 22:50 ` Daniel Walker
2018-11-12 23:11 ` David Woodhouse
2018-11-12 23:40 ` Daniel Walker
2018-11-12 23:43 ` David Woodhouse
2018-11-13 0:06 ` Daniel Walker
2018-11-13 21:01 ` Daniel Walker
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