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 C59AC1917F2 for ; Mon, 30 Sep 2024 14:55:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727708104; cv=none; b=VqKBcjgMBVP4JG2ExuKHLlWvzqJCK3HRscwQZSCpBUlMOhJnOZUl+IU7mLloT4NDEmDEaU3UT1K6bSippowU1SqDHnf6zhdS/5iK1zrqPzgp3/4fMKRK4VkYKcKqPvgz/UbfqZfNFog9MT9dwWUw+tFwJe1ez7+OBqj2z/12WqU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727708104; c=relaxed/simple; bh=a5vPzdsten2P2ffAMQmHIusfCCNiu1TFnIjnvY/TPH0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=H0E8OzbyVn/OjTQ4Kie7IJUKyfsW10IMj18QzfHfakyv7LTDhpz/8prkGHb7NkpXkETGw4zuYM6uhvQ8m82pjWGCYUs2IeyZbkP8TSK3f+spLyMB3yHqwhzihL79Tn05TKdjyxw7XtaskOspyWZZKbLjCehxmzS04VvCtdmTYsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A175C4CEC7; Mon, 30 Sep 2024 14:55:03 +0000 (UTC) Date: Mon, 30 Sep 2024 10:55:50 -0400 From: Steven Rostedt To: Liao Chang Cc: , , , Subject: Re: [PATCH v2] function_graph: Improve fgraph LRU data initialization Message-ID: <20240930105550.564d5a67@gandalf.local.home> In-Reply-To: <20240930071031.3694979-1-liaochang1@huawei.com> References: <20240930071031.3694979-1-liaochang1@huawei.com> X-Mailer: Claws Mail 3.20.0git84 (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 Mon, 30 Sep 2024 07:10:31 +0000 Liao Chang wrote: > This patch uses [first ... last] = value to initialize fgraph_array[]. > And use fgraph_lru_next and fgraph_lru_last as the indicator of > initialization. The only thing this patch does is to allow the use of [first...last] annotation for initialization. What actual benefit does that give us? In other words, why would I want to apply this? Just so that we can use [first...last] annotation with the added cost of having to manage setting fgraph_lru_next and fgraph_lru_last to -1 and then comparing them? Personally, I find the original code easier to maintain, as it's simple and doesn't add extra management. -- Steve > > v2->v1: > Fixup the build error reported by kernel test robot . > Since some architectures use ftrace_graph_entry_stub() for the static > ftrace scenario, then restore the definition without static keyword in > the original patch [1]. And rebasing patch to next-20240927. > > [1] https://lore.kernel.org/all/20240912111550.1752115-1-liaochang1@huawei.com > > Signed-off-by: Liao Chang > --- > kernel/trace/fgraph.c | 54 +++++++++++++++++++++---------------------- > 1 file changed, 27 insertions(+), 27 deletions(-) > > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index d7d4fb403f6f..eb2fbc0338c7 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -172,20 +172,41 @@ enum { > DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); > int ftrace_graph_active; > > -static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; > +int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, > + struct fgraph_ops *gops) > +{ > + return 0; > +} > + > +static void ftrace_graph_ret_stub(struct ftrace_graph_ret *trace, > + struct fgraph_ops *gops) > +{ > +} > + > +static struct fgraph_ops fgraph_stub = { > + .entryfunc = ftrace_graph_entry_stub, > + .retfunc = ftrace_graph_ret_stub, > +}; > + > +static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE] = { > + [0 ... FGRAPH_ARRAY_SIZE - 1] = &fgraph_stub, > +}; > static unsigned long fgraph_array_bitmask; > > /* LRU index table for fgraph_array */ > static int fgraph_lru_table[FGRAPH_ARRAY_SIZE]; > -static int fgraph_lru_next; > -static int fgraph_lru_last; > +static int fgraph_lru_next = -1; > +static int fgraph_lru_last = -1; > > /* Initialize fgraph_lru_table with unused index */ > static void fgraph_lru_init(void) > { > - int i; > + if ((fgraph_lru_next >= 0) && (fgraph_lru_last >= 0)) > + return; > > - for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) > + fgraph_lru_next = fgraph_lru_last = 0; > + > + for (int i = 0; i < FGRAPH_ARRAY_SIZE; i++) > fgraph_lru_table[i] = i; > } > > @@ -483,22 +504,6 @@ int __weak ftrace_disable_ftrace_graph_caller(void) > } > #endif > > -int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, > - struct fgraph_ops *gops) > -{ > - return 0; > -} > - > -static void ftrace_graph_ret_stub(struct ftrace_graph_ret *trace, > - struct fgraph_ops *gops) > -{ > -} > - > -static struct fgraph_ops fgraph_stub = { > - .entryfunc = ftrace_graph_entry_stub, > - .retfunc = ftrace_graph_ret_stub, > -}; > - > static struct fgraph_ops *fgraph_direct_gops = &fgraph_stub; > DEFINE_STATIC_CALL(fgraph_func, ftrace_graph_entry_stub); > DEFINE_STATIC_CALL(fgraph_retfunc, ftrace_graph_ret_stub); > @@ -1250,12 +1255,7 @@ int register_ftrace_graph(struct fgraph_ops *gops) > > mutex_lock(&ftrace_lock); > > - if (!fgraph_array[0]) { > - /* The array must always have real data on it */ > - for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) > - fgraph_array[i] = &fgraph_stub; > - fgraph_lru_init(); > - } > + fgraph_lru_init(); > > i = fgraph_lru_alloc_index(); > if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) {