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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 0D936C43441 for ; Wed, 21 Nov 2018 04:55:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C921F21104 for ; Wed, 21 Nov 2018 04:55:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="H5BInUlC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C921F21104 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727128AbeKUP2p (ORCPT ); Wed, 21 Nov 2018 10:28:45 -0500 Received: from mail-pl1-f195.google.com ([209.85.214.195]:33049 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbeKUP2p (ORCPT ); Wed, 21 Nov 2018 10:28:45 -0500 Received: by mail-pl1-f195.google.com with SMTP id z23so3648754plo.0 for ; Tue, 20 Nov 2018 20:55:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=aqhDjAmEJk+ZSXKkfcKTbF/IA2KObuibwBf5UluFCPg=; b=H5BInUlCJZT0qs/tQs9UG/gwDIzTfYODpS6hBFDnFOWQQMcJLAXIblEETFsDH3V5oV xwBGW6z2iGGbNsm9yAAH73R12XQQ05+KDHDhekZ/8OdZLtBBq4zWkttDqgXcsUyTVQg2 tu9sOK1b60SmgP0cjutLNBt3iqNl6mn7u6BENMsO1+7vtN/iZGhgSOgweooeXFSWjONw 8SvsxKUrM/OPPlQKmPWnJ7Cll6CKNjiv61cZnn0hGfkEIw6iqtsRBk2e1fsg+6MZSmWB ZzLrBspBaahON0+RN5wBuFTZEv742p1SZxqocHeT0nevX2brRVPQsZYzA9MPX3wN8th9 BTOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=aqhDjAmEJk+ZSXKkfcKTbF/IA2KObuibwBf5UluFCPg=; b=cyebwj5MBE4CS+qUDEEV11iUdmND5Z1FHtSza4dcYm6S1HpnSWSChAV029pbU33gHW Abi2QxdCd7BxMKg8n6KbZhrARFtAUYlY9VLBB7/VcRjrIGSTVM2P30PY3de1c1aYmeG9 fq6lvMVBll9SrX4zGFPgbYWkP4AJl7D71Qr9ey6Eovxtvyr1rhvqlkHTvGPrv1ICvV6+ OiYNb9Po6DAsYqDe2PBSr4m/6CylUnA7UGsWYPQDjL95cyUGUSBAOxDxaJmc1lUkm76Y n8lJvzdKxNO1B3OdZvVkGs4rQj/mwM6UlzC+uWmmyzdMZHmqlgEaqG7wIVmU8QKyrLQm ykjw== X-Gm-Message-State: AA+aEWbvgIv/4xEVhesbVStfhMgXjdqXpVL5zKUrktKBDLWAw7Ftrd4+ Q+EM7MapqTprbtkhR0k8xBvrF49E X-Google-Smtp-Source: AFSGD/V6Qj5nryR3bm0/8jdHFEseADi/lnTm+55N/JXl5mGjp0DFF8BQ68rxF06m8EMxlDs8L7zl9A== X-Received: by 2002:a17:902:ab84:: with SMTP id f4mr5115774plr.207.1542776155212; Tue, 20 Nov 2018 20:55:55 -0800 (PST) Received: from localhost ([211.246.69.120]) by smtp.gmail.com with ESMTPSA id u137sm56846643pfc.140.2018.11.20.20.55.53 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 20 Nov 2018 20:55:54 -0800 (PST) Date: Wed, 21 Nov 2018 13:55:51 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Andrew Morton , LKML , Sergey Senozhatsky Subject: Re: [PATCH 4/6] zram: support idle page writeback Message-ID: <20181121045551.GC599@jagdpanzerIV> References: <20181116072035.155108-1-minchan@kernel.org> <20181116072035.155108-5-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181116072035.155108-5-minchan@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (11/16/18 16:20), Minchan Kim wrote: > + zram_set_flag(zram, index, ZRAM_UNDER_WB); > + zram_slot_unlock(zram, index); > + if (zram_bvec_read(zram, &bvec, index, 0, NULL)) { > + zram_slot_lock(zram, index); > + zram_clear_flag(zram, index, ZRAM_UNDER_WB); > + zram_slot_unlock(zram, index); > + continue; > + } > + > + bio_init(&bio, &bio_vec, 1); > + bio_set_dev(&bio, zram->bdev); > + bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9); > + bio.bi_opf = REQ_OP_WRITE | REQ_SYNC; > + > + bio_add_page(&bio, bvec.bv_page, bvec.bv_len, > + bvec.bv_offset); > + /* > + * XXX: A single page IO would be inefficient for write > + * but it would be not bad as starter. > + */ > + ret = submit_bio_wait(&bio); > + if (ret) { > + zram_slot_lock(zram, index); > + zram_clear_flag(zram, index, ZRAM_UNDER_WB); > + zram_slot_unlock(zram, index); > + continue; > + } Just a thought, I wonder if it will make sense (and if it will be possible) to writeback idle _compressed_ objects. Right now we decompress, say, a perfectly fine 400-byte compressed object to a PAGE_SIZE-d object and then push it to the WB device. In this particular case it has a x10 bigger IO pressure on flash. If we can write/read compressed object then we will write and read 400-bytes, instead of PAGE_SIZE. -ss