From: "'Naveen N. Rao'" <naveen.n.rao@linux.vnet.ibm.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"ast@fb.com" <ast@fb.com>,
"daniel@iogearbox.net" <daniel@iogearbox.net>,
"davem@davemloft.net" <davem@davemloft.net>
Subject: Re: [PATCH 3/3] powerpc: bpf: implement in-register swap for 64-bit endian operations
Date: Fri, 13 Jan 2017 23:22:01 +0530 [thread overview]
Message-ID: <20170113175201.GD3470@naverao1-tp.localdomain> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DB02635FB@AcuExch.aculab.com>
On 2017/01/13 05:17PM, David Laight wrote:
> From: Naveen N. Rao
> > Sent: 13 January 2017 17:10
> > Generate instructions to perform the endian conversion using registers,
> > rather than generating two memory accesses.
> >
> > The "way easier and faster" comment was obviously for the author, not
> > the processor.
>
> That rather depends on whether the processor has a store to load forwarder
> that will satisfy the read from the store buffer.
> I don't know about ppc, but at least some x86 will do that.
Interesting - good to know that.
However, I don't think powerpc does that and in-register swap is likely
faster regardless. Note also that gcc prefers this form at higher
optimization levels.
Thanks,
Naveen
next prev parent reply other threads:[~2017-01-13 17:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 17:10 [PATCH 1/3] powerpc: bpf: remove redundant check for non-null image Naveen N. Rao
2017-01-13 17:10 ` [PATCH 2/3] powerpc: bpf: flush the entire JIT buffer Naveen N. Rao
2017-01-13 20:10 ` Alexei Starovoitov
2017-01-13 22:55 ` Daniel Borkmann
2017-01-27 0:40 ` [2/3] " Michael Ellerman
2017-01-13 17:10 ` [PATCH 3/3] powerpc: bpf: implement in-register swap for 64-bit endian operations Naveen N. Rao
2017-01-13 17:17 ` David Laight
2017-01-13 17:52 ` 'Naveen N. Rao' [this message]
2017-01-15 15:00 ` Benjamin Herrenschmidt
2017-01-23 19:22 ` 'Naveen N. Rao'
2017-01-24 16:13 ` David Laight
2017-01-24 16:25 ` 'Naveen N. Rao'
2017-01-13 20:09 ` [PATCH 1/3] powerpc: bpf: remove redundant check for non-null image Alexei Starovoitov
2017-01-16 18:38 ` David Miller
2017-01-23 17:14 ` Naveen N. Rao
2017-01-27 0:40 ` [1/3] " Michael Ellerman
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