From: Richard Henderson <rth@twiddle.net>
To: Paolo Bonzini <pbonzini@redhat.com>,
"Emilio G. Cota" <cota@braap.org>,
QEMU Developers <qemu-devel@nongnu.org>,
MTTCG Devel <mttcg@greensocs.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
"Sergey Fedorov" <serge.fdrv@gmail.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Peter Crosthwaite" <crosthwaite.peter@gmail.com>
Subject: Re: [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash
Date: Tue, 5 Apr 2016 09:07:57 -0700 [thread overview]
Message-ID: <5703E2DD.3020103@twiddle.net> (raw)
In-Reply-To: <5703DE37.3080306@redhat.com>
On 04/05/2016 08:48 AM, Paolo Bonzini wrote:
> I think it's fine to use the struct. The exact size of the struct
> varies from 3 to 5 32-bit words, so it's hard to write nice
> size-dependent code for the hash.
I don't think it is. We have 3 integers. It is trivial to create a simple
function of 2 multiplies, two adds, and a remainder.
Take the primes from the xxhash.h, for example:
(phys_pc * PRIME32_2 + pc * PRIME32_3 + flags)
% PRIME32_1
& (CODE_GEN_PHYS_HASH_SIZE - 1)
Obviously, some bucket measurements should be taken, but I can well imagine
that this might perform just as well as the fully generic hasher.
r~
next prev parent reply other threads:[~2016-04-05 16:08 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-05 5:30 [Qemu-devel] [PATCH 00/10] tb hash improvements Emilio G. Cota
2016-04-05 5:30 ` [Qemu-devel] [PATCH 01/10] translate-all: add missing fold of tb_ctx into tcg_ctx Emilio G. Cota
2016-04-05 8:49 ` Paolo Bonzini
2016-04-05 5:30 ` [Qemu-devel] [PATCH 02/10] compiler.h: add QEMU_CACHELINE + QEMU_ALIGN() + QEMU_CACHELINE_ALIGNED Emilio G. Cota
2016-04-05 7:57 ` Peter Maydell
2016-04-05 17:24 ` Emilio G. Cota
2016-04-05 18:01 ` Peter Maydell
2016-04-05 19:13 ` Emilio G. Cota
2016-04-05 8:49 ` Paolo Bonzini
2016-04-05 12:57 ` Lluís Vilanova
2016-04-05 12:58 ` Peter Maydell
2016-04-05 15:29 ` Paolo Bonzini
2016-04-05 16:23 ` Lluís Vilanova
2016-04-05 16:31 ` Richard Henderson
2016-04-05 16:56 ` Peter Maydell
2016-04-05 19:02 ` Lluís Vilanova
2016-04-05 19:15 ` Richard Henderson
2016-04-05 20:09 ` Lluís Vilanova
2016-04-06 11:44 ` Paolo Bonzini
2016-04-06 12:02 ` Laurent Desnogues
2016-04-05 5:30 ` [Qemu-devel] [PATCH 03/10] seqlock: remove optional mutex Emilio G. Cota
2016-04-06 8:38 ` Alex Bennée
2016-04-05 5:30 ` [Qemu-devel] [PATCH 04/10] seqlock: rename write_lock/unlock to write_begin/end Emilio G. Cota
2016-04-06 8:42 ` Alex Bennée
2016-04-05 5:30 ` [Qemu-devel] [PATCH 05/10] include: add spinlock wrapper Emilio G. Cota
2016-04-05 8:51 ` Paolo Bonzini
2016-04-06 15:51 ` Alex Bennée
2016-04-05 5:30 ` [Qemu-devel] [PATCH 06/10] include: add xxhash.h Emilio G. Cota
2016-04-06 11:39 ` Alex Bennée
2016-04-06 22:59 ` Emilio G. Cota
2016-04-05 5:30 ` [Qemu-devel] [PATCH 07/10] tb hash: hash phys_pc, pc, and flags with xxhash Emilio G. Cota
2016-04-05 15:41 ` Richard Henderson
2016-04-05 15:48 ` Paolo Bonzini
2016-04-05 16:07 ` Richard Henderson [this message]
2016-04-05 19:40 ` Emilio G. Cota
2016-04-05 21:08 ` Richard Henderson
2016-04-06 0:52 ` Emilio G. Cota
2016-04-06 11:52 ` Paolo Bonzini
2016-04-06 17:44 ` Emilio G. Cota
2016-04-06 18:23 ` Paolo Bonzini
2016-04-06 18:27 ` Richard Henderson
2016-04-07 0:37 ` Emilio G. Cota
2016-04-07 8:46 ` Paolo Bonzini
2016-04-05 16:33 ` Laurent Desnogues
2016-04-05 17:19 ` Richard Henderson
2016-04-06 6:06 ` Laurent Desnogues
2016-04-06 17:32 ` Emilio G. Cota
2016-04-06 17:42 ` Richard Henderson
2016-04-07 8:12 ` Laurent Desnogues
2016-04-05 5:30 ` [Qemu-devel] [PATCH 08/10] qht: QEMU's fast, resizable and scalable Hash Table Emilio G. Cota
2016-04-05 9:01 ` Paolo Bonzini
2016-04-05 15:50 ` Richard Henderson
2016-04-08 10:27 ` Alex Bennée
2016-04-19 23:03 ` Emilio G. Cota
2016-04-05 5:30 ` [Qemu-devel] [PATCH 09/10] qht: add test program Emilio G. Cota
2016-04-08 10:45 ` Alex Bennée
2016-04-19 23:06 ` Emilio G. Cota
2016-04-20 7:50 ` Alex Bennée
2016-04-05 5:30 ` [Qemu-devel] [PATCH 10/10] tb hash: track translated blocks with qht Emilio G. Cota
2016-04-08 12:39 ` Alex Bennée
2016-04-05 8:47 ` [Qemu-devel] [PATCH 00/10] tb hash improvements Alex Bennée
2016-04-05 9:01 ` Paolo Bonzini
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