From: Linus Torvalds <torvalds@linux-foundation.org>
To: George Spelvin <linux@sciencehorizons.net>
Cc: "J. Bruce Fields" <bfields@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v3 06/10] fs/namei.c: Improve dcache hash function
Date: Thu, 2 Jun 2016 09:35:37 -0700 [thread overview]
Message-ID: <CA+55aFwGXb4QfbNBkgET7Ouwk3v5t7rVGanbdO-Mju6r4C6f7A@mail.gmail.com> (raw)
In-Reply-To: <20160602023101.7364.qmail@ns.sciencehorizons.net>
On Wed, Jun 1, 2016 at 7:31 PM, George Spelvin
<linux@sciencehorizons.net> wrote:
>
> I could use two more iterations of HASH_MIX() or something similar,
> then just take the x value, but that's 6 cycles. If a multiply is
> 4 or 5 cycles, that's a net loss.
Yes. Especially since the multiply will often end up more able to be
run in parallel with other things.
> But worrying about that is the reason I left provision for arch-specific
> hooks, and I'm already working on the first: the PA-RISC doesn't have
> an integer multiplier at all, although the FPU can do 32-bit integer
> multiplies.
Don't worry about pa-risc. There may be a handful of users, where even
"users" is more of a "boot up occasionally just for perverse fun"
rather than anything else.
That's true of at least half the architectures we support - the only
ones that really matter and where performance is a real isseu are
currently x86, arm and powerpc.
Linus
next prev parent reply other threads:[~2016-06-02 16:35 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CA+55aFxPSW+84KfQ1N_WmND-wtvgj2zQm8nFPkRcc+gyU=uing@mail.gmail.com>
2016-05-25 7:20 ` [PATCH 00/10] String hash improvements George Spelvin
2016-05-25 8:00 ` Geert Uytterhoeven
2016-05-25 8:11 ` George Spelvin
2016-05-25 8:50 ` Geert Uytterhoeven
2016-05-25 9:07 ` George Spelvin
2016-05-25 16:08 ` Linus Torvalds
2016-05-28 19:57 ` [PATCH v3 " George Spelvin
2016-05-28 19:57 ` [PATCH v3 01/10] Pull out string hash to <linux/stringhash.h> George Spelvin
2016-05-28 19:57 ` [PATCH v3 02/10] fs/namei.c: Add hashlen_string() function George Spelvin
2016-05-28 19:57 ` [PATCH v3 03/10] <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string() George Spelvin
2016-05-28 19:57 ` [PATCH v3 04/10] Change hash_64() return value to 32 bits George Spelvin
2016-05-28 19:57 ` [PATCH v3 05/10] Eliminate bad hash multipliers from hash_32() and hash_64() George Spelvin
2016-05-28 19:57 ` [PATCH v3 06/10] fs/namei.c: Improve dcache hash function George Spelvin
2016-05-30 15:11 ` Peter Zijlstra
2016-05-30 16:06 ` George Spelvin
2016-05-30 16:27 ` Peter Zijlstra
2016-05-30 18:10 ` George Spelvin
2016-06-02 1:18 ` Linus Torvalds
2016-06-02 2:31 ` George Spelvin
2016-06-02 16:35 ` Linus Torvalds [this message]
2016-06-02 18:23 ` George Spelvin
2016-05-28 19:57 ` [PATCH v3 07/10] <linux/hash.h>: Add support for architecture-specific functions George Spelvin
2016-05-29 7:57 ` Geert Uytterhoeven
2016-05-28 19:57 ` [PATCH v3 08/10] m68k: Add <asm/hash.h> George Spelvin
2016-05-28 19:57 ` [PATCH v3 09/10] microblaze: " George Spelvin
2016-05-28 19:57 ` [PATCH v3 10/10] h8300: " George Spelvin
2016-05-28 20:47 ` [PATCH v3 00/10] String hash improvements Linus Torvalds
2016-05-28 20:54 ` George Spelvin
2016-06-02 22:59 ` [PATCH " Fubo Chen
2016-05-26 17:09 ` [PATCH v2 " George Spelvin
2016-05-25 7:21 ` [PATCH 01/10] Pull out string hash to <linux/stringhash.h> George Spelvin
2016-05-25 7:22 ` [PATCH 02/10] fs/namei.c: Add hash_string() function George Spelvin
2016-05-25 7:26 ` [PATCH 03/10] <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hash_string() George Spelvin
2016-05-25 7:28 ` [PATCH 04/10] Change hash_64() return value to 32 bits George Spelvin
2016-05-25 7:29 ` [PATCH 05/10] Eliminate bad hash multipliers from hash_32() and hash_64() George Spelvin
2016-05-25 7:31 ` [PATCH 06/10] fs/namei.c: Improve dcache hash function George Spelvin
2016-05-25 7:33 ` [PATCH 07/10] <linux/hash.h>: Add support for architecture-specific functions George Spelvin
2016-05-26 17:16 ` [PATCH v2 " George Spelvin
2016-05-25 7:34 ` [PATCH 08/10] m68k: Add <asm/archhash.h> George Spelvin
2016-05-25 7:34 ` George Spelvin
2016-05-25 8:07 ` Geert Uytterhoeven
2016-05-25 8:19 ` George Spelvin
2016-05-25 8:24 ` [PATCH 08v2/10] " George Spelvin
2016-05-25 8:48 ` Geert Uytterhoeven
2016-05-25 8:56 ` [PATCH 08/10] " Philippe De Muyter
2016-05-25 9:14 ` George Spelvin
2016-05-25 9:31 ` Andreas Schwab
2016-05-25 9:51 ` Philippe De Muyter
2016-05-25 13:24 ` Philippe De Muyter
2016-05-25 13:42 ` George Spelvin
2016-05-26 17:19 ` [PATCH v2 08/10] m68k: Add <asm/hash.h> George Spelvin
2016-05-25 7:37 ` [PATCH 09/10] microblaze: Add <asm/archhash.h> George Spelvin
2016-05-26 17:21 ` [PATCH v2 09/10] microblaze: Add <asm/hash.h> George Spelvin
2016-05-25 7:38 ` [PATCH 10/10] h8300: Add <asm/archhash.h> George Spelvin
2016-05-26 17:23 ` [PATCH v2 10/10] h8300: Add <asm/hash.h> George Spelvin
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