Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 25 May 2022 10:05:26 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Jakub =?UTF-8?B?TWF0xJtuYQ==?= <matenajakub@gmail.com>
Cc:     linux-mm@kvack.org, patches@lists.linux.dev,
        linux-kernel@vger.kernel.org, vbabka@suse.cz, mhocko@kernel.org,
        mgorman@techsingularity.net, willy@infradead.org,
        liam.howlett@oracle.com, hughd@google.com, kirill@shutemov.name,
        riel@surriel.com, peterz@infradead.org, david@redhat.com
Subject: Re: [RFC PATCH v3 6/6] [PATCH 6/6] mm: add tracing for VMA merges
Message-ID: <20220525100526.2a7a0eb7@gandalf.local.home>
In-Reply-To: <20220516125405.1675-7-matenajakub@gmail.com>
References: <20220516125405.1675-1-matenajakub@gmail.com>
        <20220516125405.1675-7-matenajakub@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Precedence: bulk

On Mon, 16 May 2022 14:54:05 +0200
Jakub Matěna <matenajakub@gmail.com> wrote:

> +	TP_fast_assign(
> +		__entry->merged = merged == 0;
> +		__entry->predecessor_different_av = merge_prev;
> +		__entry->successor_different_av = merge_next;
> +		__entry->predecessor_with_successor_different_av = merge_both;


> +		__entry->same_count = (merge_prev == AV_MERGE_SAME) +
> +			(merge_next == AV_MERGE_SAME) +
> +			(merge_both == AV_MERGE_SAME);
> +		__entry->diff_count = (merge_prev == AV_MERGE_DIFFERENT) +
> +			(merge_next == AV_MERGE_DIFFERENT) +
> +			(merge_both == AV_MERGE_DIFFERENT);
> +		__entry->failed_count = (merge_prev == AV_MERGE_FAILED) +
> +			(merge_next == AV_MERGE_FAILED) +
> +			(merge_both == AV_MERGE_FAILED);

The above looks like it can be moved into the TP_printk(), as you have the
merge_prev, next and both saved already. Why waste more ring buffer space
and execution time for information that can be derived at the time of
reading the trace event?

-- Steve


> +	),
> +
> +	TP_printk("merged=%d predecessor=%s successor=%s predecessor_with_successor=%s same_count=%d diff_count=%d failed_count=%d",
> +		__entry->merged,
> +		__print_symbolic(__entry->predecessor_different_av, AV_MERGE_TYPES),
> +		__print_symbolic(__entry->successor_different_av, AV_MERGE_TYPES),
> +		__print_symbolic(__entry->predecessor_with_successor_different_av, AV_MERGE_TYPES),
> +		__entry->same_count, __entry->diff_count, __entry->failed_count)
> +
> +);
> +