From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu, 7 Jan 2021 10:28:44 +0800
From: Fino Meng <fino.meng@linux.intel.com>
Subject: Re: Is it possible to implement a real-time API to read the files on
 the disk?
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To: =?utf-8?B?5a2Z5LiW6b6Z?= sunshilong <sunshilong369@gmail.com>
Cc: xenomai@xenomai.org

On Thu, Jan 07, 2021 at 10:03:06AM +0800, 孙世龙 sunshilong wrote:
> >depends on your use case, maybe possible to add a raw disk, only used by
> >the time critical code?
> It seems a good solution.
> It's possible to add a raw disk.
> One more question, does it could guarantee the read operation achieve a
> real-time performance by this method(i.e occupying another disk)?
> Is there still some problem that I should be aware of?
> 

raw disk is not shared, then should not mount it.
the drivers of file system and harddisk belongs to non-realtime vanilla
Linux. Choose a fastest disk (PCIE NVMe disk?), then need to implement a
RTDM driver for it, that's quite a lot of work,
those raised in my mind by far,

BR/fino

> On Wed, Jan 6, 2021 at 8:05 AM Fino Meng <fino.meng@linux.intel.com> wrote:
> >
> > On Mon, Jan 04, 2021 at 07:58:53PM +0800, 孙世龙 sunshilong via Xenomai wrote:
> > > Is it possible to implement a real-time API to read the files on the disk?
> > >
> > > As far as I know, there is no such an interface now, but is it
> > > possible to achieve this goal?
> > >
> > > I would be grateful to have some help with this question.
> > >
> > > Best Regards
> > > Sunshilong
> > >
> >
> > my first thinking, disks are heavily shared resources in a general OS, if
> > realtime API occupy it for a long time, non-realtime thread all have to
> > wait.
> >
> > read a file is too much slow compare a realtime thread's latency/jitter
> > scope (< 20us)
> >
> > depends on your use case, maybe possible to add a raw disk, only used by
> > the time critical code?
> >
> > BR/fino