Re: [PATCH] mm: add config for readahead window

[Wei Wang]

On Fri, Mar 16, 2018 at 2:59 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
wrote:

> On Fri, 16 Mar 2018 21:51:48 +0000 Wei Wang <wei.vince.wang@xxxxxxxxx>
wrote:

> > On Fri, Mar 16, 2018, 14:33 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
wrote:
> >
> > > On Fri, 16 Mar 2018 11:25:08 -0700 Wei Wang <wvw@xxxxxxxxxx> 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.

~90ms savings from an Android device compared to setting the window later
in userland.
I was using 'week' words as I agree with Linus's point - it is all about
the storage, so the savings are not universal indeed.