From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Siddhesh Poyarekar <siddhesh@gotplt.org>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH v10 5/6] nss: Optimize nss_hash in nss_hash.c
Date: Thu, 19 May 2022 17:21:33 -0500 [thread overview]
Message-ID: <CAFUsyfJ3b1YdeCX704J+iWzUt3_WmJVmKNAfAr06bnbgnuNmXw@mail.gmail.com> (raw)
In-Reply-To: <63f1682e-239d-ae85-c37b-af0f1121a587@gotplt.org>
On Thu, May 19, 2022 at 10:41 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>
> On 18/05/2022 22:56, Noah Goldstein via Libc-alpha wrote:
> > The prior unrolling didn't really do much as it left the dependency
> > chain between iterations. Unrolled the loop for 4 so 4x multiplies
> > could be pipelined in out-of-order machines.
> >
> > Results for __nss_hash
> > Benchmarked on Tigerlake: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
> >
> > Time as Geometric Mean of N=25 runs
> > Geometric of all benchmark New / Old: 0.845
> > type, length, New Time, Old Time, New Time / Old Time
> > fixed, 0, 4.019, 3.729, 1.078
> > fixed, 1, 4.95, 5.707, 0.867
> > fixed, 2, 5.152, 5.657, 0.911
> > fixed, 3, 4.641, 5.721, 0.811
> > fixed, 4, 5.551, 5.81, 0.955
> > fixed, 5, 6.525, 6.552, 0.996
> > fixed, 6, 6.711, 6.561, 1.023
> > fixed, 7, 6.715, 6.767, 0.992
> > fixed, 8, 7.874, 7.915, 0.995
> > fixed, 9, 8.888, 9.767, 0.91
> > fixed, 10, 8.959, 9.762, 0.918
> > fixed, 11, 9.188, 9.987, 0.92
> > fixed, 12, 9.708, 10.618, 0.914
> > fixed, 13, 10.393, 11.14, 0.933
> > fixed, 14, 10.628, 12.097, 0.879
> > fixed, 15, 10.982, 12.965, 0.847
> > fixed, 16, 11.851, 14.429, 0.821
> > fixed, 32, 24.334, 34.414, 0.707
> > fixed, 64, 55.618, 86.688, 0.642
> > fixed, 128, 118.261, 224.36, 0.527
> > fixed, 256, 256.183, 538.629, 0.476
> > random, 2, 11.194, 11.556, 0.969
> > random, 4, 17.516, 17.205, 1.018
> > random, 8, 23.501, 20.985, 1.12
> > random, 16, 28.131, 29.212, 0.963
> > random, 32, 35.436, 38.662, 0.917
> > random, 64, 45.74, 58.868, 0.777
> > random, 128, 75.394, 121.963, 0.618
> > random, 256, 139.524, 260.726, 0.535
> > ---
> > nss/nss_hash.c | 92 ++++++++++++++++++++++----------------------------
> > 1 file changed, 41 insertions(+), 51 deletions(-)
> >
> > diff --git a/nss/nss_hash.c b/nss/nss_hash.c
> > index f9e17d068a..1d3787e675 100644
> > --- a/nss/nss_hash.c
> > +++ b/nss/nss_hash.c
> > @@ -19,74 +19,64 @@
> >
> > /* This is from libc/db/hash/hash_func.c, hash3 is static there */
> > /*
> > - * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
> > + * This is INCREDIBLY ugly, but fast. We break the string up into 4 byte
> > * units. On the first time through the loop we get the "leftover bytes"
> > - * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
> > - * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
> > - * this routine is heavily used enough, it's worth the ugly coding.
> > + * (len % 4). On every other iteration, we perform a 4x unrolled version
> > + * HASHC. Further unrolling does not appear to help.
> > *
> > * OZ's original sdbm hash
> > */
> > uint32_t
> > __nss_hash (const void *keyarg, size_t len)
> > {
> > + enum
> > + {
> > + HASH_CONST_P0 = 1, /* (uint32_t)(65599 ^ 0). */
> > + HASH_CONST_P1 = 65599, /* (uint32_t)(65599 ^ 1). */
> > + HASH_CONST_P2 = 8261505, /* (uint32_t)(65599 ^ 2). */
> > + HASH_CONST_P3 = 780587199, /* (uint32_t)(65599 ^ 3). */
> > + HASH_CONST_P4 = 1139564289 /* (uint32_t)(65599 ^ 4). */
> > + };
> > +
> > const unsigned char *key;
> > - size_t loop;
> > uint32_t h;
> >
> > -#define HASHC h = *key++ + 65599 * h
> > +#define HASHC h = *key++ + HASH_CONST_P1 * h
> >
> > h = 0;
> > key = keyarg;
> > if (len > 0)
> > {
> > - loop = (len + 8 - 1) >> 3;
> > - switch (len & (8 - 1))
> > - {
> > - case 0:
> > - do
> > - {
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 7:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 6:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 5:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 4:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 3:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 2:
> > - HASHC;
> > - /* FALLTHROUGH */
> > - case 1:
> > - HASHC;
> > - }
> > - while (--loop);
> > - }
> > - }
> > - return h;
> > -}
> > + switch ((len & (4 - 1)))
> > + {
> > + case 0:
> > + /* h starts out as zero so no need to include the multiply. */
> > + h = *key++;
> > + /* FALLTHROUGH */
> > + case 3:
> > + HASHC;
> > + /* FALLTHROUGH */
> > + case 2:
> > + HASHC;
> > + /* FALLTHROUGH */
> > + case 1:
> > + HASHC;
> > + /* FALLTHROUGH */
> > + }
> >
> > -/* For testing/benchmarking purposes. */
> > -static uint32_t
> > -__simple_nss_hash (const void *keyarg, size_t len)
> > -{
> > - const unsigned char *key;
> > - size_t i;
> > - uint32_t h = 0;
> > - key = keyarg;
> > -
> > - for (i = 0; i < len; ++i)
> > - h = *key++ + 65599 * h;
> > + uint32_t c0, c1, c2, c3;
> > + for (--len; len >= 4; len -= 4)
> > + {
> > + c0 = (unsigned char) *(key + 0);
> > + c1 = (unsigned char) *(key + 1);
> > + c2 = (unsigned char) *(key + 2);
> > + c3 = (unsigned char) *(key + 3);
> > + h = HASH_CONST_P4 * h + HASH_CONST_P3 * c0 + HASH_CONST_P2 * c1
> > + + HASH_CONST_P1 * c2 + HASH_CONST_P0 * c3;
> >
> > + key += 4;
> > + }
> > + }
> > return h;
> > }
> >
>
> This bottom bit should get dropped in 3/6 (and not have
> __simple_nss_hash in two places) and then reintroduced here.
Fixed in V11.
>
> Thanks,
> Siddhesh
next prev parent reply other threads:[~2022-05-19 22:21 UTC|newest]
Thread overview: 167+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 4:12 [PATCH v1 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-04-14 4:12 ` [PATCH v1 2/6] elf: Add tests for the hash functions in dl-hash.h Noah Goldstein
2022-04-14 4:12 ` [PATCH v1 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-04-14 4:12 ` [PATCH v1 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-04-14 4:12 ` [PATCH v1 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-04-14 4:12 ` [PATCH v1 6/6] elf: Optimize __dl_new_hash in dl-hash.h Noah Goldstein
2022-04-14 4:32 ` [PATCH v1 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked H.J. Lu
2022-04-14 14:56 ` Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 " Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-04-25 15:39 ` Florian Weimer
2022-04-25 15:59 ` Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-04-25 15:38 ` Florian Weimer
2022-04-25 15:58 ` Noah Goldstein
2022-04-26 8:35 ` Florian Weimer
2022-04-26 21:39 ` Noah Goldstein
2022-04-27 10:48 ` Florian Weimer
2022-04-27 15:02 ` Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-04-14 14:55 ` [PATCH v2 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-04-25 15:58 ` [PATCH v3 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-04-25 16:01 ` [PATCH v3 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Adhemerval Zanella
2022-04-25 16:18 ` Noah Goldstein
2022-04-25 15:59 ` [PATCH v1 " Adhemerval Zanella
2022-04-25 16:16 ` Noah Goldstein
2022-04-25 16:35 ` [PATCH v3 " Noah Goldstein
2022-04-25 16:35 ` [PATCH v3 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-04-25 16:35 ` [PATCH v3 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-04-27 10:39 ` Florian Weimer
2022-04-27 16:24 ` Noah Goldstein
2022-04-25 16:35 ` [PATCH v3 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-04-25 16:36 ` [PATCH v3 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-04-27 10:47 ` Florian Weimer
2022-04-25 16:36 ` [PATCH v3 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-04-27 10:43 ` Florian Weimer
2022-04-27 16:25 ` Noah Goldstein
2022-04-27 15:02 ` Alexander Monakov
[not found] ` <CAFUsyfKeocq4VAusvnggq-NR=tOQTjrD0Z6r3CYCTjGQ=tGGSw@mail.gmail.com>
[not found] ` <f54f1ec9-fc31-283f-bce9-59fd8bda98ad@ispras.ru>
2022-04-27 16:23 ` Noah Goldstein
2022-04-28 18:03 ` Alexander Monakov
2022-05-04 18:04 ` Alexander Monakov
2022-05-05 11:07 ` Alexander Monakov
2022-05-05 15:10 ` Noah Goldstein
2022-05-05 15:26 ` Alexander Monakov
2022-05-05 18:03 ` Noah Goldstein
2022-05-05 19:37 ` Alexander Monakov
2022-05-05 22:51 ` Noah Goldstein
2022-04-27 16:19 ` [PATCH v4 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-04-27 16:19 ` [PATCH v4 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-04-27 16:19 ` [PATCH v4 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-04-27 16:20 ` [PATCH v4 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-04-27 16:20 ` [PATCH v4 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-04-27 16:20 ` [PATCH v4 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-09 17:17 ` [PATCH v5 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-10 11:58 ` Adhemerval Zanella
2022-05-10 15:04 ` [PATCH v6 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-05-10 15:04 ` [PATCH v6 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-10 15:04 ` [PATCH v6 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-10 15:04 ` [PATCH v6 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-10 15:04 ` [PATCH v6 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-10 15:04 ` [PATCH v6 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-10 15:29 ` H.J. Lu
2022-05-10 15:31 ` H.J. Lu
2022-05-10 16:49 ` Alexander Monakov
2022-05-10 17:17 ` Noah Goldstein
2022-05-10 17:40 ` Alexander Monakov
2022-05-10 23:30 ` [PATCH v7 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-05-10 23:30 ` [PATCH v7 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-10 23:30 ` [PATCH v7 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-10 23:30 ` [PATCH v7 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-10 23:30 ` [PATCH v7 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-10 23:30 ` [PATCH v7 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-10 23:46 ` H.J. Lu
2022-05-11 3:07 ` Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-11 3:06 ` [PATCH v8 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-16 14:12 ` Siddhesh Poyarekar
2022-05-16 14:31 ` Alexander Monakov
2022-05-16 16:23 ` Siddhesh Poyarekar
2022-05-16 16:38 ` Noah Goldstein
2022-05-16 16:44 ` Siddhesh Poyarekar
2022-05-16 20:32 ` Noah Goldstein
2022-05-16 18:09 ` Alexander Monakov
2022-05-16 18:47 ` Siddhesh Poyarekar
2022-05-16 19:28 ` Alexander Monakov
2022-05-16 19:35 ` Noah Goldstein
2022-05-16 19:41 ` Alexander Monakov
2022-05-16 19:47 ` Adhemerval Zanella
2022-05-16 20:00 ` Alexander Monakov
2022-05-16 20:08 ` Adhemerval Zanella
2022-05-16 20:27 ` Alexander Monakov
2022-05-16 19:48 ` Noah Goldstein
2022-05-16 20:33 ` Alexander Monakov
2022-05-16 21:40 ` Noah Goldstein
2022-05-17 1:45 ` Siddhesh Poyarekar
2022-05-16 13:56 ` [PATCH v8 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Siddhesh Poyarekar
2022-05-16 20:31 ` Noah Goldstein
2022-05-16 20:29 ` [PATCH v9 " Noah Goldstein
2022-05-16 20:30 ` [PATCH v9 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-17 4:19 ` Siddhesh Poyarekar
2022-05-18 17:29 ` Noah Goldstein
2022-05-16 20:30 ` [PATCH v9 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-17 4:32 ` Siddhesh Poyarekar
2022-05-18 17:30 ` Noah Goldstein
2022-05-16 20:30 ` [PATCH v9 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-17 4:52 ` Siddhesh Poyarekar
2022-05-18 17:33 ` Noah Goldstein
2022-05-16 20:30 ` [PATCH v9 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-17 5:11 ` Siddhesh Poyarekar
2022-05-18 17:34 ` Noah Goldstein
2022-05-18 17:35 ` Noah Goldstein
2022-05-16 20:30 ` [PATCH v9 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-17 5:12 ` Siddhesh Poyarekar
2022-05-18 17:38 ` Noah Goldstein
2022-05-19 15:59 ` Siddhesh Poyarekar
2022-05-19 16:54 ` DJ Delorie
2022-05-17 3:34 ` [PATCH v9 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Siddhesh Poyarekar
2022-05-18 17:28 ` Noah Goldstein
2022-05-18 17:26 ` [PATCH v10 " Noah Goldstein
2022-05-18 17:26 ` [PATCH v10 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-19 14:49 ` Siddhesh Poyarekar
2022-05-18 17:26 ` [PATCH v10 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-19 15:09 ` Siddhesh Poyarekar
2022-05-19 15:40 ` Siddhesh Poyarekar
2022-05-19 22:20 ` Noah Goldstein
2022-05-18 17:26 ` [PATCH v10 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-19 15:34 ` Siddhesh Poyarekar
2022-05-19 22:20 ` Noah Goldstein
2022-05-18 17:26 ` [PATCH v10 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-19 15:41 ` Siddhesh Poyarekar
2022-05-19 22:21 ` Noah Goldstein [this message]
2022-05-18 17:26 ` [PATCH v10 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-18 17:32 ` H.J. Lu
2022-05-18 17:39 ` Noah Goldstein
2022-05-19 7:53 ` Siddhesh Poyarekar
2022-05-19 15:55 ` Siddhesh Poyarekar
2022-05-19 22:22 ` Noah Goldstein
2022-05-19 14:47 ` [PATCH v10 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Siddhesh Poyarekar
2022-05-19 14:50 ` Noah Goldstein
2022-05-19 14:56 ` Siddhesh Poyarekar
2022-05-19 22:17 ` [PATCH v11 " Noah Goldstein
2022-05-19 22:17 ` [PATCH v11 2/6] elf: Add tests for the dl hash funcs (_dl_new_hash and _dl_elf_hash) Noah Goldstein
2022-05-19 22:19 ` Noah Goldstein
2022-05-19 22:18 ` [PATCH v11 3/6] nss: Add tests for the nss_hash in nss_hash.h Noah Goldstein
2022-05-23 7:42 ` Siddhesh Poyarekar
2022-05-19 22:18 ` [PATCH v11 4/6] benchtests: Add benchtests for dl_elf_hash, dl_new_hash and nss_hash Noah Goldstein
2022-05-23 7:44 ` Siddhesh Poyarekar
2022-05-19 22:18 ` [PATCH v11 5/6] nss: Optimize nss_hash in nss_hash.c Noah Goldstein
2022-05-23 7:44 ` Siddhesh Poyarekar
2022-05-19 22:18 ` [PATCH v11 6/6] elf: Optimize _dl_new_hash in dl-new-hash.h Noah Goldstein
2022-05-23 7:46 ` Siddhesh Poyarekar
2022-05-19 22:18 ` [PATCH v11 1/6] elf: Refactor dl_new_hash so it can be tested / benchmarked Noah Goldstein
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