From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 78CE528E2E for ; Mon, 11 Dec 2023 12:31:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BCtBzmDC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64061C433C7; Mon, 11 Dec 2023 12:31:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702297898; bh=2YrHH+HuC91ba8HcfvIfejtI7HytiTGHhIwK+ff//AE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=BCtBzmDCymkLD2leoITdd8OLzwp7C+lqgyb+dP2XCyEF7n+M0IhYKTAIbTLYeSC1X 4m6EW/Il7Pd0/N5kPwnP3vLAmueP90GzVxL1Y2QF+m/O7v2M2aRpVWWq5WD+wOENzb 8nYHB2SyWaonh1wsCYeepu1ECCcP7nXzme8fLFPU84oeoQ4Tiwbl3hVjCCJ8jOUiVy dC1PqKNHVQclRJyaIputlbl+Ou2QRlhnrQOhidGVdaY/pHNAqE6Kz0h+zUmMi90Xr7 sSiN73BRSvdBYw1PEdcxm0O9U3UbD7PY9aC9jEqISaAx8WljylQjCS13o7IywV36ac C+q8gOhuaLaEQ== Date: Mon, 11 Dec 2023 21:31:34 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: LKML , Linux trace kernel , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers Subject: Re: [PATCH] tracing: Update snapshot buffer on resize if it is allocated Message-Id: <20231211213134.bd21cf745b8c5a0892891946@kernel.org> In-Reply-To: <20231210225447.48476a6a@rorschach.local.home> References: <20231210225447.48476a6a@rorschach.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 10 Dec 2023 22:54:47 -0500 Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > The snapshot buffer is to mimic the main buffer so that when a snapshot is > needed, the snapshot and main buffer are swapped. When the snapshot buffer > is allocated, it is set to the minimal size that the ring buffer may be at > and still functional. When it is allocated it becomes the same size as the > main ring buffer, and when the main ring buffer changes in size, it should > do. nit: There seems two "when the snapshot buffer is allocated" case, maybe latter "it" means main buffer? > > Currently, the resize only updates the snapshot buffer if it's used by the > current tracer (ie. the preemptirqsoff tracer). But it needs to be updated > anytime it is allocated. > > When changing the size of the main buffer, instead of looking to see if > the current tracer is utilizing the snapshot buffer, just check if it is > allocated to know if it should be updated or not. > > Also fix typo in comment just above the code change. > Looks good to me. Reviewed-by: Masami Hiramatsu (Google) BTW, the historical naming leads this kind of issues. Maybe we'd better to rename 'max_buffer' to 'snapshot_buffer'? Thanks, > Cc: stable@vger.kernel.org > Fixes: ad909e21bbe69 ("tracing: Add internal tracing_snapshot() functions") > Signed-off-by: Steven Rostedt (Google) > --- > kernel/trace/trace.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index aa8f99f3e5de..6c79548f9574 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -6348,7 +6348,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr, > if (!tr->array_buffer.buffer) > return 0; > > - /* Do not allow tracing while resizng ring buffer */ > + /* Do not allow tracing while resizing ring buffer */ > tracing_stop_tr(tr); > > ret = ring_buffer_resize(tr->array_buffer.buffer, size, cpu); > @@ -6356,7 +6356,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr, > goto out_start; > > #ifdef CONFIG_TRACER_MAX_TRACE > - if (!tr->current_trace->use_max_tr) > + if (!tr->allocated_snapshot) > goto out; > > ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu); > -- > 2.42.0 > -- Masami Hiramatsu (Google)