From: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/4] ARCv2: entry: Reduce perf intr return path
Date: Tue, 14 Nov 2017 11:28:02 +0100 [thread overview]
Message-ID: <20171114102802.GA3165@worktop.lehotels.local> (raw)
In-Reply-To: <1510092784-19942-5-git-send-email-vgupta@synopsys.com>
On Tue, Nov 07, 2017 at 02:13:04PM -0800, Vineet Gupta wrote:
> In the more likely case of returning to kernel from perf interrupt, do a
> fast path returning w/o bothering about CONFIG_PREEMPT etc
I think this needs more explaining and certainly also deserves a code
comment.
Is the argument something along these lines?
Assumes the interrupt will never set TIF_NEED_RESCHED;
therefore no preemption is ever required on return from
the interrupt.
What do you (on ARC) do about irq_work ?
> +ENTRY(handle_interrupt_pct)
> +
> + INTERRUPT_PROLOGUE irq
> +
> + IRQ_DISABLE
> +
> + lr r0, [ICAUSE]
> +
> + bl.d arch_do_IRQ
> + mov r1, sp
> +
> + ld r0, [sp, PT_status32] ; returning to User/Kernel Mode
> + btst r0, STATUS_U_BIT
> + bnz resume_user_mode_begin
> +
> + clri
> + b .Lisr_ret_fast_path_to_k
> +
> +END(handle_interrupt_pct)
next prev parent reply other threads:[~2017-11-14 10:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 22:13 [PATCH 0/4] ARC perf updates Vineet Gupta
2017-11-07 22:13 ` [PATCH 1/4] ARCv2: perf: tweak overflow interrupt Vineet Gupta
2017-11-07 22:13 ` [PATCH 2/4] ARCv2: perf: optimize given that num counters <= 32 Vineet Gupta
2017-11-07 22:13 ` [PATCH 3/4] ARC: perf: avoid vmalloc backed mmap Vineet Gupta
2017-11-07 22:13 ` [PATCH 4/4] ARCv2: entry: Reduce perf intr return path Vineet Gupta
2017-11-14 10:28 ` Peter Zijlstra [this message]
2017-11-14 23:01 ` Vineet Gupta
2017-11-15 10:18 ` Peter Zijlstra
2017-11-17 23:42 ` Vineet Gupta
2017-11-21 23:26 ` Vineet Gupta
2017-11-13 21:30 ` [PATCH 0/4] ARC perf updates Vineet Gupta
2017-11-21 22:09 ` Vineet Gupta
2017-11-21 23:13 ` Peter Zijlstra
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