From: Catalin Marinas <email@example.com> To: firstname.lastname@example.org Cc: email@example.com, Dave.Martin@arm.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Mark Brown <email@example.com> Subject: Re: sve_user_discard Date: Fri, 21 May 2021 10:12:54 +0100 [thread overview] Message-ID: <20210521091254.GA6675@arm.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Thu, May 20, 2021 at 04:02:03PM -0700, email@example.com wrote: > This is regarding sve_user_disable(CPACR_EL1_ZEN_EL0EN) on every system > call. If a userspace task is using SVE instructions and making sys calls in > between, it would impact the performance of the thread. On every SVE > instructions after SVC/system call, it would trap to EL1. > > I think by setting CPACR_EL1_ZEN_EL0EN flag, the processor faults when it > runs an SVE instruction. This approach may be taken as part of FPSIMD > registers switching optimizations. Can below portion of the code use > thread.fpsimd_cpu and fpsimd_last_state variables to avoid clearing > CPACR_EL1_ZEN_EL0EN for this kind of use cases? There were attempts over the past couple of years to optimise the syscall return use-case. I think the latest is this one: https://firstname.lastname@example.org I'll let Mark comment on his plans for reviving the series. Do you happen to have some realistic workload that would be improved by this? We can always write a micro-benchmark but I wonder how much this matters in the real world. -- Catalin _______________________________________________ linux-arm-kernel mailing list email@example.com http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next parent reply other threads:[~2021-05-21 9:14 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <firstname.lastname@example.org> 2021-05-21 9:12 ` Catalin Marinas [this message] 2021-05-21 11:54 ` sve_user_discard Mark Brown
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20210521091254.GA6675@arm.com \ --email@example.com \ --cc=Dave.Martin@arm.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --subject='Re: sve_user_discard' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).