linux-kernel - Re: [PATCH v8 20/24] erofs: introduce generic decompression backend

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Message-ID: <20190830165217.GB107220@architecture4>
Date:   Sat, 31 Aug 2019 00:52:17 +0800
From:   Gao Xiang <gaoxiang25@...wei.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     <linux-fsdevel@...r.kernel.org>, <devel@...verdev.osuosl.org>,
        "Alexander Viro" <viro@...iv.linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Theodore Ts'o <tytso@....edu>, Pavel Machek <pavel@...x.de>,
        David Sterba <dsterba@...e.cz>,
        Amir Goldstein <amir73il@...il.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Dave Chinner <david@...morbit.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Jan Kara <jack@...e.cz>,
        Richard Weinberger <richard@....at>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        <linux-erofs@...ts.ozlabs.org>, Chao Yu <yuchao0@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Li Guifu <bluce.liguifu@...wei.com>,
        Fang Wei <fangwei1@...wei.com>
Subject: Re: [PATCH v8 20/24] erofs: introduce generic decompression backend

Hi Christoph,

On Fri, Aug 30, 2019 at 09:35:34AM -0700, Christoph Hellwig wrote:
> On Thu, Aug 15, 2019 at 12:41:51PM +0800, Gao Xiang wrote:
> > +static bool use_vmap;
> > +module_param(use_vmap, bool, 0444);
> > +MODULE_PARM_DESC(use_vmap, "Use vmap() instead of vm_map_ram() (default 0)");
> 
> And how would anyone know which to pick?

It has significant FIO benchmark difference on sequential read least on arm64...
I have no idea whether all platform vm_map_ram() behaves better than vmap(),
so I leave an option for users here...

Thanks,
Gao Xiang