From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail-yb1-f195.google.com ([209.85.219.195]:35474 "EHLO
        mail-yb1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1726593AbeIZQTV (ORCPT
        <rfc822;linux-fsdevel@vger.kernel.org>);
        Wed, 26 Sep 2018 12:19:21 -0400
Received: by mail-yb1-f195.google.com with SMTP id o63-v6so11076255yba.2
        for <linux-fsdevel@vger.kernel.org>; Wed, 26 Sep 2018 03:07:09 -0700 (PDT)
MIME-Version: 1.0
References: <20180906123706.28691-1-const@MakeLinux.com> <CAE7jHC_+NkmqUQx937v4eWwOjDALzxStW3L1t3YUxhMKmtWjBg@mail.gmail.com>
 <CAJfpeguqOnuZOQMNb4U3tZt=+tFumsd3nLWrEOh9fCpDgRQ7tQ@mail.gmail.com> <ef5fb36737924682b34277f80203300f@jd.com>
In-Reply-To: <ef5fb36737924682b34277f80203300f@jd.com>
From: Constantine Shulyupin <const@makelinux.com>
Date: Wed, 26 Sep 2018 13:06:56 +0300
Message-ID: <CAE7jHC-gYyH--H_FMkZM8=UoEMS+RkzwUF15DvuAdrMnFBWM+Q@mail.gmail.com>
Subject: Re: [PATCH v4] fuse: add max_pages option
To: =?UTF-8?B?5YiY56GV54S2?= <liushuoran@jd.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
        "open list:FUSE: FILESYSTEM IN USERSPACE"
        <linux-fsdevel@vger.kernel.org>, Jonathan Corbet <corbet@lwn.net>,
        mitsuo.hayasaka.hu@hitachi.com, Amir Goldstein <amir73il@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8BIT
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

Hi Shuoran,

On Wed, Sep 26, 2018 at 12:40 PM 刘硕然 <liushuoran@jd.com> wrote:
> I haven't tested the patch yet. But after reviewing the patch, I don't see anything related to BDI_CAP_STRICTLIMIT. So would you please explain a little bit more? Thanks.

Bigger size of request reduces total number of requests and reduces
overhead of per request operations.

> PS: I did try increasing FUSE_MAX_PAGES_PER_REQ, but it seemed not helping in my scenario(writeback cache enabled, 4K writes, total write size is not very large).

To utilize FUSE_MAX_PAGES_PER_REQ in kernel it is must to increase
KERNEL_BUF_PAGES it libfuse too. I have libfuse patch with
configurable max_pages.

But 4K writes will not benefit from increase of request size, which
now is 128K and proposed size is 1M.

Thanks