Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: John Savard <quadibloc@servername.invalid>
Newsgroups: comp.arch
Subject: Re: Privilege Levels Below User
Date: Tue, 11 Jun 2024 13:30:10 -0600
Organization: A noiseless patient Spider
Lines: 14
Message-ID: <9b9h6jtuengblsscovsh7qc652lmao4vt8@4ax.com>
References: <jai66jd4ih4ejmek0abnl4gvg5td4obsqg@4ax.com> <h0ib6j576v8o37qu1ojrsmeb5o88f29upe@4ax.com> <2024Jun9.185245@mips.complang.tuwien.ac.at> <38ob6jl9sl3ceb0qugaf26cbv8lk7hmdil@4ax.com> <2024Jun10.091648@mips.complang.tuwien.ac.at> <o32f6jlq2qpi9s1u8giq521vv40uqrkiod@4ax.com> <lcq749F7sotU1@mid.individual.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Date: Tue, 11 Jun 2024 21:30:11 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="f752231138247ec5b6f53ce61cda1d0c";
	logging-data="1275443"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+hH7XB79IVMm4DRMhgLC0NASZ6fOK4ofo="
Cancel-Lock: sha1:V+dZZj1FbA/mcjxPgtd0XvvxsIc=
X-Newsreader: Forte Free Agent 3.3/32.846
Bytes: 1867

On Tue, 11 Jun 2024 08:54:16 +0300, Niklas Holsti
<niklas.holsti@tidorum.invalid> wrote:

>Not always. If the mistakenly speculated cache-fetch /evicted/ some 
>other data from the (finite-sized) cache, and the evicted data are 
>needed later on the /true/ execution path, the mistakenly speculated 
>fetch has a /negative/ effect on performance. (This kind of "timing 
>anomaly" is very bothersome in static WCET analysis.)

Ouch. Another argument for having a victim cache. And a benefit of
doing it in what is apparently Mitch Alsup's way - holding off cache
updates until instruction retirement.

John Savard