From: Nathan Bossart <nathandbossart@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: John Naylor <john.naylor@enterprisedb.com>
Cc: John Naylor <jcnaylor@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: optimize lookups in snapshot [sub]xip arrays
Date: Tue, 2 Aug 2022 16:43:57 -0700
Message-ID: <20220802234357.GA802740@nathanxps13> (raw)
In-Reply-To: <20220802225539.nm7bgkwvkpzgib5x@awork3.anarazel.de>
References: <20220713170950.GA3116318@nathanxps13>
<20220715200857.nm2gc4weixwlwbnx@awork3.anarazel.de>
<20220717035957.GA3631071@nathanxps13>
<20220725190419.GA4095199@nathanxps13>
<20220726181906.7l4ulzjdblnanclm@alap3.anarazel.de>
<20220728213423.GA408719@nathanxps13>
<CAFBsxsE14aHKR6gr+rEeFJKaBq8sgXctonwpWw3G7twaePHkVA@mail.gmail.com>
<20220730053811.GA417958@nathanxps13>
<20220802221301.GA742739@nathanxps13>
<20220802225539.nm7bgkwvkpzgib5x@awork3.anarazel.de>
On Tue, Aug 02, 2022 at 03:55:39PM -0700, Andres Freund wrote:
> FWIW, I'd split the introduction of the helper and the use of it in snapmgr
> into separate patches.
Will do.
> On 2022-08-02 15:13:01 -0700, Nathan Bossart wrote:
>> diff --git a/src/include/c.h b/src/include/c.h
>> index d35405f191..2c1a47bc28 100644
>> --- a/src/include/c.h
>> +++ b/src/include/c.h
>> @@ -371,6 +371,14 @@ typedef void (*pg_funcptr_t) (void);
>> #endif
>> #endif
>>
>> +/*
>> + * Are SSE2 intrinsics available?
>> + */
>> +#if (defined(__x86_64__) || defined(_M_AMD64))
>> +#include <emmintrin.h>
>> +#define USE_SSE2
>> +#endif
>> +
>
> It doesn't strike me as a good idea to include this in every single
> translation unit in pg. That header (+dependencies) isn't small.
>
> I'm on board with normalizing defines for SSE availability somewhere central
> though.
Yeah, this is just a temporary hack for now. It'll go away once the
defines for SSE2 availability are committed.
>> +/*
>> + * pg_linearsearch_uint32
>> + *
>> + * Returns the address of the first element in 'base' that equals 'key', or
>> + * NULL if no match is found.
>> + */
>> +#ifdef USE_SSE2
>> +pg_attribute_no_sanitize_alignment()
>> +#endif
>
> What's the deal with this annotation? Needs a comment.
Will do. c.h suggests that this should only be used for x86-specific code.
>> +static inline uint32 *
>> +pg_linearsearch_uint32(uint32 key, uint32 *base, uint32 nelem)
>
> Hm. I suspect this could be a bit faster if we didn't search for the offset,
> but just for presence in the array? Most users don't need the offset.
Just under half of the callers in 0002 require the offset, but I don't know
if any of those are worth optimizing in the first place. I'll change it
for now. It's easy enough to add it back in the future if required.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, andres@anarazel.de, john.naylor@enterprisedb.com, jcnaylor@gmail.com
Subject: Re: optimize lookups in snapshot [sub]xip arrays
In-Reply-To: <20220802234357.GA802740@nathanxps13>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox