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From: Peter Zijlstra <peterz@infradead.org>
To: Changbin Du <changbin.du@gmail.com>
Cc: linux-arch@vger.kernel.org, linux-s390@vger.kernel.org,
	linux-parisc@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	linux-sh@vger.kernel.org, x86@kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-mips@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	Jessica Yu <jeyu@kernel.org>,
	sparclinux@vger.kernel.org, linux-kbuild@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 05/11] ftrace: create memcache for hash entries
Date: Mon, 26 Aug 2019 09:44:37 +0200
Message-ID: <20190826074437.GM2369@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190825132330.5015-6-changbin.du@gmail.com>

On Sun, Aug 25, 2019 at 09:23:24PM +0800, Changbin Du wrote:
> When CONFIG_FTRACE_FUNC_PROTOTYPE is enabled, thousands of
> ftrace_func_entry instances are created. So create a dedicated
> memcache to enhance performance.
> 
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
>  kernel/trace/ftrace.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index a314f0768b2c..cfcb8dad93ea 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -94,6 +94,8 @@ struct ftrace_ops *function_trace_op __read_mostly = &ftrace_list_end;
>  /* What to set function_trace_op to */
>  static struct ftrace_ops *set_function_trace_op;
>  
> +struct kmem_cache *hash_entry_cache;
> +
>  static bool ftrace_pids_enabled(struct ftrace_ops *ops)
>  {
>  	struct trace_array *tr;
> @@ -1169,7 +1171,7 @@ static int add_hash_entry(struct ftrace_hash *hash, unsigned long ip,
>  {
>  	struct ftrace_func_entry *entry;
>  
> -	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> +	entry = kmem_cache_alloc(hash_entry_cache, GFP_KERNEL);
>  	if (!entry)
>  		return -ENOMEM;
>  
> @@ -6153,6 +6155,15 @@ void __init ftrace_init(void)
>  	if (ret)
>  		goto failed;
>  
> +	hash_entry_cache = kmem_cache_create("ftrace-hash",
> +					     sizeof(struct ftrace_func_entry),
> +					     sizeof(struct ftrace_func_entry),
> +					     0, NULL);
> +	if (!hash_entry_cache) {
> +		pr_err("failed to create ftrace hash entry cache\n");
> +		goto failed;
> +	}

Wait what; you already have then in the binary image, now you're
allocating extra memory for each of them?

Did you look at what ORC does? Is the binary search really not fast
enough?

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Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-25 13:23 [PATCH 00/11] ftrace: add support for recording function parameters and return value Changbin Du
2019-08-25 13:23 ` [PATCH 01/11] ftrace: move recordmcount tools to scripts/ftrace Changbin Du
2019-08-26 22:44   ` Steven Rostedt
2019-08-28 23:41     ` Changbin Du
2019-08-25 13:23 ` [PATCH 02/11] ftrace: introduce new building tool funcprototype Changbin Du
2019-08-25 13:23 ` [PATCH 03/11] asm-generic: add generic dwarf definition Changbin Du
2019-08-26  7:42   ` Peter Zijlstra
2019-08-26 22:25     ` Changbin Du
2019-08-25 13:23 ` [PATCH 04/11] ftrace/hash: add private data field Changbin Du
2019-08-25 13:23 ` [PATCH 05/11] ftrace: create memcache for hash entries Changbin Du
2019-08-26  7:44   ` Peter Zijlstra [this message]
2019-08-26 22:35     ` Changbin Du
2019-08-25 13:23 ` [PATCH 06/11] ftrace: process function prototype data in vmlinux and modules Changbin Du
2019-08-25 13:23 ` [PATCH 07/11] ftrace: prepare arch specific interfaces for function prototype feature Changbin Du
2019-08-25 13:23 ` [PATCH 08/11] ftrace: introduce core part of function prototype recording Changbin Du
2019-08-25 13:23 ` [PATCH 09/11] x86_64: add function prototype recording support Changbin Du
2019-08-25 13:23 ` [PATCH 10/11] ftrace: add doc for new option record-funcproto Changbin Du
2019-08-25 13:23 ` [PATCH 11/11] MAINTAINERS: make scripts/ftrace/ maintained Changbin Du

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