From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= Subject: [PATCH] read-cache: avoid memcpy in expand_name_field in index v4 Date: Mon, 18 Mar 2013 19:58:02 +0700 Message-ID: <1363611482-1015-1-git-send-email-pclouds@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Junio C Hamano , =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= To: git@vger.kernel.org X-From: git-owner@vger.kernel.org Mon Mar 18 13:58:39 2013 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UHZeA-0008Lt-CX for gcvg-git-2@plane.gmane.org; Mon, 18 Mar 2013 13:58:38 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751922Ab3CRM6L convert rfc822-to-quoted-printable (ORCPT ); Mon, 18 Mar 2013 08:58:11 -0400 Received: from mail-da0-f46.google.com ([209.85.210.46]:36967 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751651Ab3CRM6K (ORCPT ); Mon, 18 Mar 2013 08:58:10 -0400 Received: by mail-da0-f46.google.com with SMTP id y19so4048dan.33 for ; Mon, 18 Mar 2013 05:58:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:from:to:cc:subject:date:message-id:x-mailer:mime-version :content-type:content-transfer-encoding; bh=oWfCvP1kGnvpvp/RGhaFeb5HJD49r54ORiohSeuN7DU=; b=oV4rmq8iHvEGo6TBN/diN6JOCx5hsI2AlOtfkavjGTyKKGYrhOpJils5Rz9CbqwLkt /5dAmz4iT1a3jSHVJTUZqQUmzS2a32/AAjBfie4P7lEJJ3oKePJWf8D88PxK6peshkFS NQW1u3kDXivrD/FIeg8Qj/1qE5h0pdI0gtRih6ZrhRsYLvV4mYkZJ1szlNQHAIOTQC00 OyUz8gFOADOfHZA2sdWpvGSCnaemLsxuUA+cVIniART2m3maU1Jd+y0ggJj968X/ZJOt R6Ss6CxiJeZ2ZCIj8JBtamhM5PRuyE5t5MGaVfBX+LaIWiPCZKtfKbWPiFnFkbA0I4a3 uhag== X-Received: by 10.68.204.164 with SMTP id kz4mr32704441pbc.158.1363611489802; Mon, 18 Mar 2013 05:58:09 -0700 (PDT) Received: from lanh ([115.74.61.42]) by mx.google.com with ESMTPS id yr10sm8161837pab.6.2013.03.18.05.58.06 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 18 Mar 2013 05:58:08 -0700 (PDT) Received: by lanh (sSMTP sendmail emulation); Mon, 18 Mar 2013 19:58:03 +0700 X-Mailer: git-send-email 1.8.2.83.gc99314b Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: perf reports memcpy at the the 6th position [1] in "git status -uno" using index v4, and strbuf_remove() in expand_name_field() accounts for 25% of that. What we need here is a simple string cut and a cheaper strbuf_setlen() should be enough. After this change, memcpy drops down to the 13th position [2] and is dominated by read_index_from. [1] before + 15.74% git git [.] blk_SHA1_Block + 13.22% git [kernel.kallsyms] [k] link_path_walk + 10.91% git [kernel.kallsyms] [k] __d_lookup + 8.17% git [kernel.kallsyms] [k] strncpy_from_user + 4.75% git [kernel.kallsyms] [k] memcmp + 2.42% git libc-2.11.2.so [.] memcpy [2] after + 16.30% git git [.] blk_SHA1_Block + 13.43% git [kernel.kallsyms] [k] link_path_walk + 11.45% git [kernel.kallsyms] [k] __d_lookup + 8.73% git [kernel.kallsyms] [k] strncpy_from_user + 5.14% git [kernel.kallsyms] [k] memcmp + 2.29% git [kernel.kallsyms] [k] do_lookup + 2.21% git libc-2.11.2.so [.] 0x6daf6 + 1.98% git [kernel.kallsyms] [k] _atomic_dec_and_lock + 1.98% git [kernel.kallsyms] [k] _raw_spin_lock + 1.86% git [kernel.kallsyms] [k] acl_permission_check + 1.61% git [kernel.kallsyms] [k] kmem_cache_free + 1.59% git git [.] unpack_trees + 1.47% git libc-2.11.2.so [.] memcpy Signed-off-by: Nguy=E1=BB=85n Th=C3=A1i Ng=E1=BB=8Dc Duy --- I was after something else when I noticed this. Seems like a simple and safe change. read-cache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/read-cache.c b/read-cache.c index 827ae55..8c443aa 100644 --- a/read-cache.c +++ b/read-cache.c @@ -1354,7 +1354,7 @@ static unsigned long expand_name_field(struct str= buf *name, const char *cp_) =20 if (name->len < len) die("malformed name field in the index"); - strbuf_remove(name, name->len - len, len); + strbuf_setlen(name, name->len - len); for (ep =3D cp; *ep; ep++) ; /* find the end */ strbuf_add(name, cp, ep - cp); --=20 1.8.2.83.gc99314b