From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from msa.smtpout.orange.fr (smtp-68.smtpout.orange.fr [80.12.242.68]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BAF84155734; Mon, 15 Apr 2024 20:48:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.12.242.68 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713214091; cv=none; b=mFUfkhi8SmEK3CobjmoDHPLWHducd80coVq+iotRWTBteGwf0jJ3VK10GjXw+bXfcMH2vaJ4NV1NmVEyOxk/py2Z+bg56S6lVHFtQoOc0ZRQ+Qgc3DX7tT5wzZmVTjyH3askQQzSoGXB+x5OlLxWz/TjNJdIDr+8R6Wo3yID7qI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713214091; c=relaxed/simple; bh=OXUn3oOBfuYnTTy1mRu7lO/Z7jMxLafr2xQIIy2r0mI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FROabLKez9A3/ZiRZMsqYlQ9eN1tqQuKfvhW6S0qaFGABTcm+tLGREAAwytiEhvwJprX761VNvnfYH33Wqwphj8El+R7kryPQd+ydY1XcRLN/r5tnFnmy38ClldPvg9vnalvpMrifCKeJWwvi0tuFpgGC/9vB7dkg3CnuCFrqJY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=wanadoo.fr; spf=pass smtp.mailfrom=wanadoo.fr; dkim=pass (2048-bit key) header.d=wanadoo.fr header.i=@wanadoo.fr header.b=K6eZcu0g; arc=none smtp.client-ip=80.12.242.68 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=wanadoo.fr Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=wanadoo.fr Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=wanadoo.fr header.i=@wanadoo.fr header.b="K6eZcu0g" Received: from [192.168.1.18] ([86.243.17.157]) by smtp.orange.fr with ESMTPA id wTF9rwTfAUEo7wTF9rKczA; Mon, 15 Apr 2024 22:48:01 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wanadoo.fr; s=t20230301; t=1713214081; bh=S7uRgOT3iqhsU0DFa0D2HmmuEAbosFRiIzoeYLAMrm8=; h=Message-ID:Date:MIME-Version:Subject:To:From; b=K6eZcu0gztGMQv7qYT7noG/tiTulzOJYXNLMMvyf4z1n5jh04K24Gxm12D/Hr0qh2 oHRKVbot6M3PXazewZLyPvNuBcM7L6pLo0wv/HefPHx9OgqjY6TQzZN2qSW1+j5iJb C0TQDfggobQt3/DjsvQovsKQ4kG7a2N6/2yyMPBbddMJFOW9Bzno03XjjK+9W5436m C0bMXP6XrQ0PP7BYFN5Sd8JzMp3QeHiGq7ZPdhTuAusvVI1aOQL4By3DNuH0WsMU1h G4B/jAMVUs4WT+h+jai5YCsyDTxKD4XSxhQkbUJl2Rm9QPDFEKoDVC5N0sqaZwfHH/ 1BFeRPZEdgywQ== X-ME-Helo: [192.168.1.18] X-ME-Auth: Y2hyaXN0b3BoZS5qYWlsbGV0QHdhbmFkb28uZnI= X-ME-Date: Mon, 15 Apr 2024 22:48:01 +0200 X-ME-IP: 86.243.17.157 Message-ID: <4b1a4cc5-e057-4944-be69-d25f28645256@wanadoo.fr> Date: Mon, 15 Apr 2024 22:47:59 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] seq_file: Optimize seq_puts() To: Alexander Viro , Christian Brauner , Jan Kara Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <5c4f7ad7b88f5026940efa9c8be36a58755ec1b3.1704374916.git.christophe.jaillet@wanadoo.fr> Content-Language: en-MW From: Christophe JAILLET In-Reply-To: <5c4f7ad7b88f5026940efa9c8be36a58755ec1b3.1704374916.git.christophe.jaillet@wanadoo.fr> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 04/01/2024 à 14:29, Christophe JAILLET a écrit : > Most of seq_puts() usages are done with a string literal. In such cases, > the length of the string car be computed at compile time in order to save > a strlen() call at run-time. seq_write() can then be used instead. > > This saves a few cycles. > > To have an estimation of how often this optimization triggers: > $ git grep seq_puts.*\" | wc -l > 3391 > > Signed-off-by: Christophe JAILLET Hi, any feed-back on this small optimisation of seq_puts()? Most of its usage would be optimized and a strlen() would be saved in all the corresponding cases. $ git grep seq_puts.*\" | wc -l 3436 $ git grep seq_puts | wc -l 3644 CJ > --- > Checked by comparing the output of a few .s files. > Here is one of these outputs: > > $ diff -u drivers/clk/clk.s.old drivers/clk/clk.s | grep -C6 seq_w > > call clk_prepare_unlock # > # drivers/clk/clk.c:3320: seq_puts(s, "}\n"); > movq %r12, %rdi # s, > + movl $2, %edx #, > movq $.LC66, %rsi #, > - call seq_puts # > + call seq_write # > call __tsan_func_exit # > # drivers/clk/clk.c:3322: } > xorl %eax, %eax # > @@ -34520,6 +34521,7 @@ > popq %rbp # > popq %r12 # > -- > # drivers/clk/clk.c:3205: seq_puts(s, "-----"); > call __sanitizer_cov_trace_pc # > + movl $5, %edx #, > movq $.LC72, %rsi #, > movq %r13, %rdi # s, > - call seq_puts # > + call seq_write # > jmp .L2134 # > .L2144: > # drivers/clk/clk.c:1793: return clk_core_get_accuracy_no_lock(core); > @@ -35225,20 +35228,23 @@ > leaq 240(%r12), %rdi #, tmp95 > call __tsan_read8 # > -- > movq %r12, %rdi # s, > + movq $.LC77, %rsi #, > # drivers/clk/clk.c:3244: struct hlist_head **lists = s->private; > movq 240(%r12), %rbp # s_9(D)->private, lists > # drivers/clk/clk.c:3246: seq_puts(s, " enable prepare protect duty hardware connection\n"); > - call seq_puts # > + call seq_write # > # drivers/clk/clk.c:3247: seq_puts(s, " clock count count count rate accuracy phase cycle enable consumer id\n"); > + movl $142, %edx #, > movq $.LC78, %rsi #, > movq %r12, %rdi # s, > - call seq_puts # > + call seq_write # > # drivers/clk/clk.c:3248: seq_puts(s, "---------------------------------------------------------------------------------------------------------------------------------------------\n"); > + movl $142, %edx #, > movq $.LC79, %rsi #, > movq %r12, %rdi # s, > - call seq_puts # > + call seq_write # > # drivers/clk/clk.c:3251: clk_prepare_lock(); > call clk_prepare_lock # > .L2207: > @@ -37511,7 +37517,7 @@ > subq $16, %rsp #, > # drivers/clk/clk.c:3082: { > --- > fs/seq_file.c | 4 ++-- > include/linux/seq_file.h | 10 +++++++++- > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/fs/seq_file.c b/fs/seq_file.c > index f5fdaf3b1572..8ef0a07033ca 100644 > --- a/fs/seq_file.c > +++ b/fs/seq_file.c > @@ -669,7 +669,7 @@ void seq_putc(struct seq_file *m, char c) > } > EXPORT_SYMBOL(seq_putc); > > -void seq_puts(struct seq_file *m, const char *s) > +void __seq_puts(struct seq_file *m, const char *s) > { > int len = strlen(s); > > @@ -680,7 +680,7 @@ void seq_puts(struct seq_file *m, const char *s) > memcpy(m->buf + m->count, s, len); > m->count += len; > } > -EXPORT_SYMBOL(seq_puts); > +EXPORT_SYMBOL(__seq_puts); > > /** > * seq_put_decimal_ull_width - A helper routine for putting decimal numbers > diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h > index 234bcdb1fba4..15abf45d62c5 100644 > --- a/include/linux/seq_file.h > +++ b/include/linux/seq_file.h > @@ -118,7 +118,15 @@ void seq_vprintf(struct seq_file *m, const char *fmt, va_list args); > __printf(2, 3) > void seq_printf(struct seq_file *m, const char *fmt, ...); > void seq_putc(struct seq_file *m, char c); > -void seq_puts(struct seq_file *m, const char *s); > +void __seq_puts(struct seq_file *m, const char *s); > +#define seq_puts(m, s) \ > +do { \ > + if (__builtin_constant_p(s)) \ > + seq_write(m, s, __builtin_strlen(s)); \ > + else \ > + __seq_puts(m, s); \ > +} while (0) > + > void seq_put_decimal_ull_width(struct seq_file *m, const char *delimiter, > unsigned long long num, unsigned int width); > void seq_put_decimal_ull(struct seq_file *m, const char *delimiter,