From: Peter Zijlstra <peterz@infradead.org>
To: Chuyi Zhou <zhouchuyi@bytedance.com>
Cc: tglx@linutronix.de, mingo@redhat.com, luto@kernel.org,
paulmck@kernel.org, muchun.song@linux.dev, bp@alien8.de,
dave.hansen@linux.intel.com, pbonzini@redhat.com,
bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 10/12] x86/mm: Move flush_tlb_info back to the stack
Date: Mon, 2 Mar 2026 15:58:48 +0100 [thread overview]
Message-ID: <20260302145848.GI1395266@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260302075216.2170675-11-zhouchuyi@bytedance.com>
On Mon, Mar 02, 2026 at 03:52:14PM +0800, Chuyi Zhou wrote:
> Commit 3db6d5a5ecaf ("x86/mm/tlb: Remove 'struct flush_tlb_info' from the
> stack") converted flush_tlb_info from stack variable to per-CPU variable.
> This brought about a performance improvement of around 3% in extreme test.
> However, it also required that all flush_tlb* operations keep preemption
> disabled entirely to prevent concurrent modifications of flush_tlb_info.
> flush_tlb* needs to send IPIs to remote CPUs and synchronously wait for
> all remote CPUs to complete their local TLB flushes. The process could
> take tens of milliseconds when interrupts are disabled or with a large
> number of remote CPUs.
>
> From the perspective of improving kernel real-time performance, this patch
> reverts flush_tlb_info back to stack variables. This is a preparation for
> enabling preemption during TLB flush in next patch.
This isn't properly justified. You've got to show that 'most' workloads
are not adversely affected by this.
Most people still swing towards performance most of the time.
next prev parent reply other threads:[~2026-03-02 14:59 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-02 7:52 [PATCH v2 00/12] Allow preemption during IPI completion waiting to improve real-time performance Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 01/12] smp: Disable preemption explicitly in __csd_lock_wait Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 02/12] smp: Enable preemption early in smp_call_function_single Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 03/12] smp: Remove get_cpu from smp_call_function_any Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 04/12] smp: Use on-stack cpumask in smp_call_function_many_cond Chuyi Zhou
2026-03-10 7:12 ` Muchun Song
2026-03-02 7:52 ` [PATCH v2 05/12] smp: Free call_function_data via RCU in smpcfd_dead_cpu Chuyi Zhou
2026-03-10 7:05 ` Muchun Song
2026-03-10 7:26 ` Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 06/12] smp: Enable preemption early in smp_call_function_many_cond Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 07/12] smp: Remove preempt_disable from smp_call_function Chuyi Zhou
2026-03-10 7:06 ` Muchun Song
2026-03-02 7:52 ` [PATCH v2 08/12] smp: Remove preempt_disable from on_each_cpu_cond_mask Chuyi Zhou
2026-03-10 7:06 ` Muchun Song
2026-03-02 7:52 ` [PATCH v2 09/12] scftorture: Remove preempt_disable in scftorture_invoke_one Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 10/12] x86/mm: Move flush_tlb_info back to the stack Chuyi Zhou
2026-03-02 14:58 ` Peter Zijlstra [this message]
2026-03-03 3:20 ` Chuyi Zhou
2026-03-05 7:01 ` Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 11/12] x86/mm: Enable preemption during native_flush_tlb_multi Chuyi Zhou
2026-03-02 7:52 ` [PATCH v2 12/12] x86/mm: Enable preemption during flush_tlb_kernel_range Chuyi Zhou
2026-03-10 6:35 ` kernel test robot
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