From: Alexander Monakov <amonakov@ispras.ru>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: Hongyu Wang <hongyu.wang@intel.com>,
gcc-patches@gcc.gnu.org, hongtao.liu@intel.com,
ubizjak@gmail.com
Subject: Re: [PATCH] doc: Reword the description of -mrelax-cmpxchg-loop [PR 107676]
Date: Tue, 15 Nov 2022 16:59:12 +0300 (MSK) [thread overview]
Message-ID: <7a41f182-1638-1a70-c0dc-b90b1985c31@ispras.ru> (raw)
In-Reply-To: <CACb0b4mxggf4jPuKGHL=PAjoFnWgm0efjYYaW3S6UjX2-XAP0Q@mail.gmail.com>
On Tue, 15 Nov 2022, Jonathan Wakely wrote:
> > How about the following:
> >
> > When emitting a compare-and-swap loop for @ref{__sync Builtins}
> > and @ref{__atomic Builtins} lacking a native instruction, optimize
> > for the highly contended case by issuing an atomic load before the
> > @code{CMPXCHG} instruction, and invoke the @code{PAUSE} instruction
> > when restarting the loop.
>
> That's much better, thanks. My only remaining quibble would be that
> "invoking" an instruction seems only marginally better than running
> one. Emitting? Issuing? Using? Adding?
Right, it should be 'using'; let me also add 'to save CPU power':
When emitting a compare-and-swap loop for @ref{__sync Builtins}
and @ref{__atomic Builtins} lacking a native instruction, optimize
for the highly contended case by issuing an atomic load before the
@code{CMPXCHG} instruction, and using the @code{PAUSE} instruction
to save CPU power when restarting the loop.
Alexander
next prev parent reply other threads:[~2022-11-15 13:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-15 3:35 Hongyu Wang
2022-11-15 10:53 ` Jonathan Wakely
2022-11-15 13:28 ` Alexander Monakov
2022-11-15 13:44 ` Jonathan Wakely
2022-11-15 13:59 ` Alexander Monakov [this message]
2022-11-16 5:15 ` Hongyu Wang
2022-11-16 7:51 ` Alexander Monakov
2022-11-16 8:29 ` Hongyu Wang
2022-11-16 10:51 ` Jonathan Wakely
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