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>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
netdev@vger.kernel.org
Subject: Re: [PATCH v3] powerpc: Implement csum_ipv6_magic in assembly
Date: Thu, 24 May 2018 14:42:06 -0500 [thread overview]
Message-ID: <20180524194206.GD17342@gate.crashing.org> (raw)
In-Reply-To: <3848a4ad-2c0e-691f-e98f-347cfe3484e8@c-s.fr>
On Thu, May 24, 2018 at 08:20:16AM +0200, Christophe LEROY wrote:
> Le 23/05/2018 à 20:34, Segher Boessenkool a écrit :
> >On Tue, May 22, 2018 at 08:57:01AM +0200, Christophe Leroy wrote:
> >>+_GLOBAL(csum_ipv6_magic)
> >>+ lwz r8, 0(r3)
> >>+ lwz r9, 4(r3)
> >>+ lwz r10, 8(r3)
> >>+ lwz r11, 12(r3)
> >>+ addc r0, r5, r6
> >>+ adde r0, r0, r7
> >>+ adde r0, r0, r8
> >>+ adde r0, r0, r9
> >>+ adde r0, r0, r10
> >>+ adde r0, r0, r11
> >>+ lwz r8, 0(r4)
> >>+ lwz r9, 4(r4)
> >>+ lwz r10, 8(r4)
> >>+ lwz r11, 12(r4)
> >>+ adde r0, r0, r8
> >>+ adde r0, r0, r9
> >>+ adde r0, r0, r10
> >>+ adde r0, r0, r11
> >>+ addze r0, r0
> >>+ rotlwi r3, r0, 16
> >>+ add r3, r0, r3
> >>+ not r3, r3
> >>+ rlwinm r3, r3, 16, 16, 31
> >>+ blr
> >>+EXPORT_SYMBOL(csum_ipv6_magic)
> >
> >Clustering the loads and carry insns together is pretty much the worst you
> >can do on most 32-bit CPUs.
>
> Oh, really ? __csum_partial is written that way too.
I thought I told you about this before? Maybe not.
> Right, now I tried interleaving the lwz and adde. I get no improvment at
> all on a 885, but I get a 15% improvment on a 8321.
It won't likely help on single-issue cores (like the one 885 has), yes.
Segher
prev parent reply other threads:[~2018-05-24 19:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-22 6:57 [PATCH v3] powerpc: Implement csum_ipv6_magic in assembly Christophe Leroy
2018-05-23 18:34 ` Segher Boessenkool
2018-05-24 6:20 ` Christophe LEROY
2018-05-24 10:18 ` Christophe Leroy
2018-05-24 19:55 ` Segher Boessenkool
2018-05-24 19:42 ` Segher Boessenkool [this message]
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