From: David Laight <David.Laight@ACULAB.COM>
To: 'Robin Murphy' <robin.murphy@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"kernel-team@android.com" <kernel-team@android.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Segher Boessenkool <segher@kernel.crashing.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: RE: [PATCH v4 05/11] arm64: csum: Disable KASAN for do_csum()
Date: Fri, 24 Apr 2020 09:41:30 +0000 [thread overview]
Message-ID: <db86e9fa88754d59ac5f8d3f4fe0f9a3@AcuMS.aculab.com> (raw)
In-Reply-To: <6efa0cc1-bd3e-b9b6-4e69-7ac05e6efe35@arm.com>
From: Robin Murphy
> Sent: 22 April 2020 12:02
..
> Sure - I have a nagging feeling that it could still do better WRT
> pipelining the loads anyway, so I'm happy to come back and reconsider
> the local codegen later. It certainly doesn't deserve to stand in the
> way of cross-arch rework.
How fast does that loop actually run?
To my mind it seems to do a lot of operations on each 64bit value.
I'd have thought that a loop based on:
sum64 = *ptr;
sum64_high = *ptr++ >> 32;
and then fixing up the result would be faster.
The x86-64 code is also bad!
On intel cpu prior to haswell a simple:
sum_64 += *ptr32++;
is faster than the current code.
(Although you can do a lot better even on ivy bridge.)
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-04-24 9:41 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 15:15 [PATCH v4 00/11] Rework READ_ONCE() to improve codegen Will Deacon
2020-04-21 15:15 ` [PATCH v4 01/11] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8 Will Deacon
2020-04-21 17:15 ` Masahiro Yamada
2020-04-21 15:15 ` [PATCH v4 02/11] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-04-21 15:15 ` [PATCH v4 03/11] net: tls: " Will Deacon
2020-04-21 15:15 ` [PATCH v4 04/11] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-04-21 15:15 ` [PATCH v4 05/11] arm64: csum: Disable KASAN for do_csum() Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 9:49 ` Mark Rutland
2020-04-22 9:49 ` Mark Rutland
2020-04-22 10:41 ` Will Deacon
2020-04-22 11:01 ` Robin Murphy
2020-04-24 9:41 ` David Laight [this message]
2020-04-24 11:00 ` Robin Murphy
2020-04-24 13:04 ` David Laight
2020-04-24 13:04 ` David Laight
2020-04-21 15:15 ` [PATCH v4 06/11] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 9:51 ` Mark Rutland
2020-04-21 15:15 ` [PATCH v4 07/11] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-24 16:31 ` Jann Horn
2020-04-24 17:11 ` Will Deacon
2020-04-24 17:43 ` Peter Zijlstra
2020-04-21 15:15 ` [PATCH v4 08/11] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-22 10:25 ` Rasmus Villemoes
2020-04-22 11:48 ` Segher Boessenkool
2020-04-22 11:48 ` Segher Boessenkool
2020-04-22 13:11 ` Will Deacon
2020-04-22 13:11 ` Will Deacon
2020-04-22 14:54 ` Will Deacon
2020-04-21 15:15 ` [PATCH v4 09/11] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-21 15:15 ` [PATCH v4 10/11] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-04-21 15:15 ` [PATCH v4 11/11] gcov: Remove old GCC 3.4 support Will Deacon
2020-04-21 15:15 ` Will Deacon
2020-04-21 17:19 ` Masahiro Yamada
2020-04-21 18:42 ` [PATCH v4 00/11] Rework READ_ONCE() to improve codegen Linus Torvalds
2020-04-21 18:42 ` Linus Torvalds
2020-04-22 8:18 ` Will Deacon
2020-04-22 11:37 ` Peter Zijlstra
2020-04-22 12:26 ` Will Deacon
2020-04-24 13:42 ` Will Deacon
2020-04-24 15:54 ` Marco Elver
2020-04-24 16:52 ` Will Deacon
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