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 94CD1155A24; Sun, 1 Sep 2024 16:20:16 +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=1725207616; cv=none; b=N+//xv9OPQk7EbQzYOF5pIqhCVmF/UUADmOt9fkPkOg89HWRccEgEjdprgG9sASTABWp3byJ+FRFoDV7sKXiA29BR6taYwKqj6jSHXDgACPrzfTf9Et898qbCIP5kn7hjGsXsP2ZtTII+BvMgfRU9uF4DhXl7xoOWoxiUPtcYTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725207616; c=relaxed/simple; bh=V9P29nbsPbhMGW+dMZjJTBOCsBtsBvNGf4tH1RW8Lxg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tKyI8Ub6m+YQwk7uC2MLzO9Ee34vaDK5zO6iiNSKxjZh3IWYE5FJa1xF7apqj71RiA9/xbl/S+JGTUAINShW/i52o4KK9zpJ+dzQlNbMqJmEpC91sPCCYjxgTNNRAWWUBJpXNP+6rFdQex3q3valF/jv10GurYDlLcGKHd7NYwo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZdIA/Yfi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ZdIA/Yfi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0472C4CEC3; Sun, 1 Sep 2024 16:20:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1725207616; bh=V9P29nbsPbhMGW+dMZjJTBOCsBtsBvNGf4tH1RW8Lxg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZdIA/Yfi98xJagLmrN7FLIDk5BE9A1/vhCK0VOiyf3R1E6iv+H9qdLJ5qOPD/ndiT DAdEzCkJ4nVrpNbZa9x4Ra4Y/VF4pBjbjMCQL5Cw9br2OgP+CvYJYKyskgtm+IUrXl e1c8OG4cHM/Ebu3kaz4Ec9LymhTb4Pu3L9PJTlV8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Przemek Kitszel , Yury Norov , Alexander Lobakin , "David S. Miller" Subject: [PATCH 4.19 07/98] bitmap: introduce generic optimized bitmap_size() Date: Sun, 1 Sep 2024 18:15:37 +0200 Message-ID: <20240901160803.960762811@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240901160803.673617007@linuxfoundation.org> References: <20240901160803.673617007@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Lobakin commit a37fbe666c016fd89e4460d0ebfcea05baba46dc upstream. The number of times yet another open coded `BITS_TO_LONGS(nbits) * sizeof(long)` can be spotted is huge. Some generic helper is long overdue. Add one, bitmap_size(), but with one detail. BITS_TO_LONGS() uses DIV_ROUND_UP(). The latter works well when both divident and divisor are compile-time constants or when the divisor is not a pow-of-2. When it is however, the compilers sometimes tend to generate suboptimal code (GCC 13): 48 83 c0 3f add $0x3f,%rax 48 c1 e8 06 shr $0x6,%rax 48 8d 14 c5 00 00 00 00 lea 0x0(,%rax,8),%rdx %BITS_PER_LONG is always a pow-2 (either 32 or 64), but GCC still does full division of `nbits + 63` by it and then multiplication by 8. Instead of BITS_TO_LONGS(), use ALIGN() and then divide by 8. GCC: 8d 50 3f lea 0x3f(%rax),%edx c1 ea 03 shr $0x3,%edx 81 e2 f8 ff ff 1f and $0x1ffffff8,%edx Now it shifts `nbits + 63` by 3 positions (IOW performs fast division by 8) and then masks bits[2:0]. bloat-o-meter: add/remove: 0/0 grow/shrink: 20/133 up/down: 156/-773 (-617) Clang does it better and generates the same code before/after starting from -O1, except that with the ALIGN() approach it uses %edx and thus still saves some bytes: add/remove: 0/0 grow/shrink: 9/133 up/down: 18/-538 (-520) Note that we can't expand DIV_ROUND_UP() by adding a check and using this approach there, as it's used in array declarations where expressions are not allowed. Add this helper to tools/ as well. Reviewed-by: Przemek Kitszel Acked-by: Yury Norov Signed-off-by: Alexander Lobakin Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/s390/cio/idset.c | 2 +- include/linux/bitmap.h | 8 +++++--- include/linux/cpumask.h | 2 +- tools/include/linux/bitmap.h | 7 ++++--- 4 files changed, 11 insertions(+), 8 deletions(-) --- a/drivers/s390/cio/idset.c +++ b/drivers/s390/cio/idset.c @@ -18,7 +18,7 @@ struct idset { static inline unsigned long bitmap_size(int num_ssid, int num_id) { - return BITS_TO_LONGS(num_ssid * num_id) * sizeof(unsigned long); + return bitmap_size(size_mul(num_ssid, num_id)); } static struct idset *idset_new(int num_ssid, int num_id) --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -212,12 +212,14 @@ extern int bitmap_print_to_pagebuf(bool #define small_const_nbits(nbits) \ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0) +#define bitmap_size(nbits) (ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE) + static inline void bitmap_zero(unsigned long *dst, unsigned int nbits) { if (small_const_nbits(nbits)) *dst = 0UL; else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); memset(dst, 0, len); } } @@ -227,7 +229,7 @@ static inline void bitmap_fill(unsigned if (small_const_nbits(nbits)) *dst = ~0UL; else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); memset(dst, 0xff, len); } } @@ -238,7 +240,7 @@ static inline void bitmap_copy(unsigned if (small_const_nbits(nbits)) *dst = *src; else { - unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); + unsigned int len = bitmap_size(nbits); memcpy(dst, src, len); } } --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -656,7 +656,7 @@ static inline int cpulist_parse(const ch */ static inline unsigned int cpumask_size(void) { - return BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long); + return bitmap_size(nr_cpumask_bits); } /* --- a/tools/include/linux/bitmap.h +++ b/tools/include/linux/bitmap.h @@ -27,13 +27,14 @@ int __bitmap_and(unsigned long *dst, con #define small_const_nbits(nbits) \ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG) +#define bitmap_size(nbits) (ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE) + static inline void bitmap_zero(unsigned long *dst, int nbits) { if (small_const_nbits(nbits)) *dst = 0UL; else { - int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long); - memset(dst, 0, len); + memset(dst, 0, bitmap_size(nbits)); } } @@ -119,7 +120,7 @@ static inline int test_and_clear_bit(int */ static inline unsigned long *bitmap_alloc(int nbits) { - return calloc(1, BITS_TO_LONGS(nbits) * sizeof(unsigned long)); + return calloc(1, bitmap_size(nbits)); } /*