From mboxrd@z Thu Jan 1 00:00:00 1970 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 9D01CC47082 for ; Mon, 31 May 2021 14:31:33 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0E88D601FC for ; Mon, 31 May 2021 14:31:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E88D601FC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4FtyQr0jhCz2ysq for ; Tue, 1 Jun 2021 00:31:32 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=ZDnKmzm+; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=xiang@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=ZDnKmzm+; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4FtyQm1v4Sz2xb8 for ; Tue, 1 Jun 2021 00:31:27 +1000 (AEST) Received: by mail.kernel.org (Postfix) with ESMTPSA id 3976461042; Mon, 31 May 2021 14:31:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622471485; bh=vOtIEAH/8MnqIBK3exH+T8JWCpnoQ7/hXA5Z+wsayH4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZDnKmzm+Ei9CQ5L5lQSqAHj5aRA19ctW6C0xSgoevmWmq0GJtYlR6ul2/4YIH0IRf vzS2uR2RpL9sBnRywg9A7K2gbPcbjrfW5dMTFI7vlx0xoAGL6QVPJLJvyxofFzrafl BAueUw48sznzLB3QJF1gBVzlJqzyQ8GAlbjLapLROIYTFO87S/zeVybM8/h737ErI3 u4ntJ/Z8yMaK/M4tYHzS6HhQRQksQ8QIMcwlYvvHYLvAUfDknFUkDZqHrFSJ52Ku5X qVdVKH1IuufBX2pZFldxAr4KLo1s9sDot7W235sTSiOOqjbo2CRR2ZeKZikfeNDQCp MwUOOqSx1pNZg== From: Gao Xiang To: linux-erofs@lists.ozlabs.org Subject: [PATCH v2 2/3] erofs-utils: README: big pcluster feature update Date: Mon, 31 May 2021 22:31:16 +0800 Message-Id: <20210531143117.6327-2-xiang@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210531143117.6327-1-xiang@kernel.org> References: <20210531143117.6327-1-xiang@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gao Xiang Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" Add some description for end users to know its usage. Link: https://lore.kernel.org/r/20210522055057.25004-2-xiang@kernel.org Signed-off-by: Gao Xiang --- README | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/README b/README index bcf30e11aa52..af9cdf11c78a 100644 --- a/README +++ b/README @@ -74,6 +74,24 @@ In addition, you could specify a higher compression level to get a (slightly) better compression ratio than the default level, e.g. $ mkfs.erofs -zlz4hc,12 foo.erofs.img foo/ +How to generate EROFS big pcluster images (Linux 5.13+) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In order to get much better compression ratios (thus better sequential +read performance for common storage devices), big pluster feature has +been introduced since linux-5.13, which is not forward-compatible with +old kernels. + +In details, -C is used to specify the maximum size of each big pcluster +in bytes, e.g. + $ mkfs.erofs -zlz4hc -C65536 foo.erofs.img foo/ + +So in that case, pcluster size can be 64KiB at most. + +Note that large pcluster size can cause bad random performance, so +please evaluate carefully in advance. Or make your own per-(sub)file +compression strategies according to file access patterns if needed. + How to generate legacy EROFS images (Linux 4.19+) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- 2.20.1