From: Thiago Macieira <thiago.macieira@intel.com>
To: Thomas Rodgers <rodgert@appliantology.com>
Cc: <trodgers@redhat.com>, <jwakely@redhat.com>, <libstdc++@gcc.gnu.org>
Subject: Re: C++2a synchronisation inefficient in GCC 11
Date: Mon, 1 Mar 2021 10:00:24 -0800 [thread overview]
Message-ID: <7309459.cE9rBlv1QQ@tjmaciei-mobl1> (raw)
In-Reply-To: <b789b26fd01d07fe505aaba83e9a1bc6@appliantology.com>
On Monday, 1 March 2021 09:46:08 PST Thomas Rodgers wrote:
> I discussed the prematureness of the contention optimization with ogiroux
> this morning. Confirming, libc++ does do this, and in his measurements it
> saves on the order of 50us.
>
> Regarding the use of _Hash_impl::hash(), that can be changed to just use the
> pointer value itself. This is what libatomic does. I'm happy to propose
> that as a subsequent patch to the most recent version of this code which I
> submitted recently.
Is the benchmark source somewhere I can take a look at?
I'm worried that it is benchmarking the wrong thing. Can we benchmark latch
and counting_semaphore instead? Those already track contention on the waitable
atomic by themselves.
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel DPG Cloud Engineering
next prev parent reply other threads:[~2021-03-01 18:00 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 22:50 Thiago Macieira
2021-02-26 11:19 ` Jonathan Wakely
2021-02-26 17:37 ` Thiago Macieira
2021-02-26 18:29 ` Jonathan Wakely
2021-02-26 19:30 ` Ville Voutilainen
2021-02-26 21:17 ` Jonathan Wakely
2021-02-26 21:18 ` Ville Voutilainen
2021-02-26 21:39 ` Jonathan Wakely
2021-02-26 18:47 ` Ville Voutilainen
2021-02-26 23:53 ` Thiago Macieira
2021-02-26 23:58 ` Ville Voutilainen
2021-02-27 0:11 ` Thiago Macieira
2021-02-27 0:18 ` Ville Voutilainen
2021-02-27 0:36 ` Thiago Macieira
2021-02-27 0:44 ` Ville Voutilainen
2021-02-27 0:53 ` Thiago Macieira
2021-02-27 1:03 ` Ville Voutilainen
2021-03-03 14:30 ` Jonathan Wakely
2021-03-03 17:07 ` Thiago Macieira
2021-03-03 17:14 ` Jonathan Wakely
2021-02-27 0:22 ` Marc Glisse
2021-02-27 0:30 ` Ville Voutilainen
2021-02-27 0:43 ` Thiago Macieira
2021-03-03 14:24 ` Jonathan Wakely
2021-03-03 17:12 ` Thiago Macieira
2021-02-26 15:59 ` [PATCH 1/5] std::latch: reduce internal implementation from ptrdiff_t to int Thiago Macieira
2021-02-26 15:59 ` [PATCH 2/5] Atomic __platform_wait: accept any 32-bit type, not just int Thiago Macieira
2021-03-03 14:34 ` Jonathan Wakely
2021-03-03 16:21 ` Jonathan Wakely
2021-03-03 17:27 ` Thiago Macieira
2021-03-03 17:34 ` Ville Voutilainen
2021-03-03 17:41 ` Jonathan Wakely
2021-02-26 15:59 ` [PATCH 3/5] std::__atomic_wait: don't use __detail::__waiter with futex Thiago Macieira
2021-02-26 15:59 ` [PATCH 4/5] barrier: use int instead of unsigned char for the phase state Thiago Macieira
2021-02-28 15:05 ` Hans-Peter Nilsson
2021-03-01 16:28 ` Thomas Rodgers
2021-03-01 17:24 ` Thiago Macieira
2021-03-01 17:38 ` Thomas Rodgers
2021-03-01 17:40 ` Thomas Rodgers
2021-03-01 18:06 ` Thiago Macieira
2021-03-01 19:08 ` Thomas Rodgers
2021-03-01 18:12 ` Ville Voutilainen
2021-03-01 19:44 ` Thiago Macieira
2021-03-01 20:35 ` Ville Voutilainen
2021-03-01 21:54 ` Thiago Macieira
2021-03-01 22:04 ` Ville Voutilainen
2021-03-01 22:21 ` Thiago Macieira
2021-03-01 22:31 ` Ville Voutilainen
2021-03-01 22:40 ` Thiago Macieira
2021-02-26 15:59 ` [PATCH 5/5] barrier: optimise by not having the hasher in a loop Thiago Macieira
2021-03-03 14:36 ` Jonathan Wakely
2021-02-26 18:14 ` [PATCH 1/5] std::latch: reduce internal implementation from ptrdiff_t to int Andreas Schwab
2021-02-26 19:08 ` Thiago Macieira
2021-02-26 19:31 ` Andreas Schwab
2021-02-27 0:13 ` Thiago Macieira
2021-02-28 21:31 ` Hans-Peter Nilsson
2021-03-01 8:56 ` Richard Biener
2021-03-03 14:56 ` Jonathan Wakely
2021-03-03 15:02 ` Andreas Schwab
2021-03-03 15:10 ` Jonathan Wakely
2021-03-03 15:37 ` Hans-Peter Nilsson
2021-03-01 16:32 ` Thomas Rodgers
2021-03-03 14:34 ` Jonathan Wakely
2021-03-03 17:14 ` Thiago Macieira
2021-03-03 17:18 ` Jonathan Wakely
2021-02-27 1:13 ` C++2a synchronisation inefficient in GCC 11 Thomas Rodgers
2021-02-27 1:29 ` Thomas Rodgers
2021-02-27 3:01 ` Thomas Rodgers
2021-03-01 17:46 ` Thomas Rodgers
2021-03-01 18:00 ` Thiago Macieira [this message]
2021-03-01 18:34 ` Thomas Rodgers
2021-03-01 19:11 ` Thiago Macieira
2021-02-27 2:02 ` Ville Voutilainen
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