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Date:   Fri, 16 Mar 2018 14:59:42 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Wei Wang <wei.vince.wang@gmail.com>
Cc:     Wei Wang <wvw@google.com>, gregkh@linuxfoundation.org,
        Todd Poynor <toddpoynor@google.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Michal Hocko <mhocko@suse.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Jan Kara <jack@suse.cz>,
        =?ISO-8859-1?Q?J=E9r=F4me?= Glisse <jglisse@redhat.com>,
        Hugh Dickins <hughd@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Sherry Cheung <SCheung@nvidia.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Huang Ying <ying.huang@intel.com>,
        Dennis Zhou <dennisz@fb.com>,
        Pavel Tatashin <pasha.tatashin@oracle.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: add config for readahead window
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On Fri, 16 Mar 2018 21:51:48 +0000 Wei Wang <wei.vince.wang@gmail.com> wrote:

> On Fri, Mar 16, 2018, 14:33 Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Fri, 16 Mar 2018 11:25:08 -0700 Wei Wang <wvw@google.com> wrote:
> >
> > > Change VM_MAX_READAHEAD value from the default 128KB to a configurable
> > > value. This will allow the readahead window to grow to a maximum size
> > > bigger than 128KB during boot, which could benefit to sequential read
> > > throughput and thus boot performance.
> >
> > You can presently run ioctl(BLKRASET) against the block device?
> >
> 
> Yeah we are doing tuning in userland after init. But this is something we
> thought could help in very early stage.
> 

"thought" and "could" are rather weak!  Some impressive performance
numbers for real-world setups would help such a patch along.