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Date: Fri, 16 Mar 2018 14:33:06 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Wei Wang <wvw@google.com>
Cc: gregkh@linuxfoundation.org, toddpoynor@google.com,
 wei.vince.wang@gmail.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 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?