From: Peter Zijlstra <peterz@infradead.org>
To: George Spelvin <linux@sciencehorizons.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
lkml <linux-kernel@vger.kernel.org>,
"J . Bruce Fields" <bfields@redhat.com>
Subject: Re: [PATCH v3 06/10] fs/namei.c: Improve dcache hash function
Date: Mon, 30 May 2016 17:11:29 +0200 [thread overview]
Message-ID: <20160530151129.GO3206@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1464465443-25305-7-git-send-email-linux@sciencehorizons.net>
On Sat, May 28, 2016 at 03:57:19PM -0400, George Spelvin wrote:
> +static inline unsigned int fold_hash(unsigned long x, unsigned long y)
> {
> + y ^= x * GOLDEN_RATIO_64;
> + y *= GOLDEN_RATIO_64;
> + return y >> 32;
> }
So does it make sense to use that pattern here too?
This code doesn't much care about performance, but wants a decent hash
from the stack of class keys.
---
kernel/locking/lockdep.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 81f1a7107c0e..c8498efcd5d9 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -309,10 +309,12 @@ static struct hlist_head chainhash_table[CHAINHASH_SIZE];
* It's a 64-bit hash, because it's important for the keys to be
* unique.
*/
-#define iterate_chain_key(key1, key2) \
- (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
- ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
- (key2))
+static inline u64 iterate_chain_key(u64 x, u64 y)
+{
+ y ^= x * GOLDEN_RATIO_64;
+ y *= GOLDEN_RATIO_64;
+ return y;
+}
void lockdep_off(void)
{
next prev parent reply other threads:[~2016-05-30 15:11 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 [this message]
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
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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