From patchwork Mon Mar 22 14:05:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 12154863 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF98AC433E2 for ; Mon, 22 Mar 2021 14:05:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6FD3F6198D for ; Mon, 22 Mar 2021 14:05:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230343AbhCVOFY (ORCPT ); Mon, 22 Mar 2021 10:05:24 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44830 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230235AbhCVOFQ (ORCPT ); Mon, 22 Mar 2021 10:05:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616421916; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=QPkSFGAEFwyxkIsg8U3iEYvQY5nY02tfAo9JoeH500U=; b=P19gsudeiEXvyiPqevCOsLwfcrYRspZaYwRtNMFmnYY6Qrd21n9vOFEHAqG/EsFQkqHBtp obNkXGoqTJFF7gnp11fYqhdwat7DhCV/VUNC6XGb0gebGUuXrzMn+LgULiGGNqIBG28w0l oCA6Ydz/wd2/X57jpwqZ3qs6Ma58ZwQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-107-q7E0KdvfM_C12LWdMVHd9w-1; Mon, 22 Mar 2021 10:05:08 -0400 X-MC-Unique: q7E0KdvfM_C12LWdMVHd9w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F147887A826; Mon, 22 Mar 2021 14:05:06 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (file01.intranet.prod.int.rdu2.redhat.com [10.11.5.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A88CB5B6A8; Mon, 22 Mar 2021 14:05:06 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (localhost [127.0.0.1]) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4) with ESMTP id 12ME56RX020189; Mon, 22 Mar 2021 10:05:06 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 12ME556x020185; Mon, 22 Mar 2021 10:05:05 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Mon, 22 Mar 2021 10:05:05 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Alexander Viro , Jens Axboe cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH] buffer: a small optimization in grow_buffers Message-ID: User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This patch replaces a loop with a "tzcnt" instruction. Signed-off-by: Mikulas Patocka Index: linux-2.6/fs/buffer.c =================================================================== --- linux-2.6.orig/fs/buffer.c +++ linux-2.6/fs/buffer.c @@ -1020,11 +1020,7 @@ grow_buffers(struct block_device *bdev, pgoff_t index; int sizebits; - sizebits = -1; - do { - sizebits++; - } while ((size << sizebits) < PAGE_SIZE); - + sizebits = PAGE_SHIFT - __ffs(size); index = block >> sizebits; /*