linux-kernel - Re: [PATCH 2/3] x86/alternatives: Move tp

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Message-ID: <20190826143647.GV2369@hirez.programming.kicks-ass.net>
Date:   Mon, 26 Aug 2019 16:36:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Nadav Amit <nadav.amit@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 2/3] x86/alternatives: Move tp_vec

On Mon, Aug 26, 2019 at 02:51:40PM +0200, Peter Zijlstra wrote:

> +#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
> +extern struct text_poke_loc tp_vec[TP_VEC_MAX];
> +extern int tp_vec_nr;

FWIW, that currently results in a batch size of 128, but I've not
noticed any delay in flipping ftrace on and off on the commandline.

Growing that buffer really shouldn't be a problem, but I'm thinking we'd
want solid performance numbers to justify it.