答复: 32bit resctrl? (was Re: [PATCH v2] fs/resctrl: fix domid loss precision issue)

[Rex Nie]

HI Peter,
	In next link, Maciej Wieczor-Retman and I talked about arm cache id. FYI
	https://lore.kernel.org/all/KL1PR0601MB57730994C0501212DF6DDC6EE6242@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
BRs
Rex

> -----邮件原件-----
> 发件人: Peter Newman <peternewman@xxxxxxxxxx>
> 发送时间: 2024年3月15日 8:05
> 收件人: Rex Nie <rex.nie@xxxxxxxxxxxxxxx>
> 抄送: james.morse@xxxxxxx; x86@xxxxxxxxxx; Luck, Tony
> <tony.luck@xxxxxxxxx>; Babu Moger <babu.moger@xxxxxxx>; Borislav
> Petkov <bp@xxxxxxxxx>; fenghua.yu@xxxxxxxxx; ilpo.jarvinen@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Reinette Chatre <reinette.chatre@xxxxxxxxx>
> 主题: Re: 32bit resctrl? (was Re: [PATCH v2] fs/resctrl: fix domid loss precision
> issue)
> 
> External Mail: This email originated from OUTSIDE of the organization!
> Do not click links, open attachments or provide ANY information unless you
> recognize the sender and know the content is safe.
> 
> 
> Hi Rex,
> 
> On Thu, Mar 14, 2024 at 8:25 AM Reinette Chatre <reinette.chatre@xxxxxxxxx>
> wrote:
> >
> > +x86 maintainers, Tony, Babu, Peter
> >
> > Hi Everybody,
> >
> > On 3/12/2024 12:53 AM, Rex Nie wrote:
> > > Below statement from mkdir_mondata_subdir function will loss
> > > precision, because it assigns int to 14 bits bitfield.
> > >       priv.u.domid = d->id;
> > >
> > > On some platforms(e.g.,x86), the max cache_id is the amount of L3
> > > caches, so it is not in the range of 0x3fff. But some platforms use
> > > higher cache_id, e.g., arm uses cache_id as locator for cache MSC.
> > > This will cause below issue if cache_id > 0x3fff likes:
> > > /sys/fs/resctrl/mon_groups/p1/mon_data/mon_L3_1048564 # cat
> > > llc_occupancy
> 
> This domain ID seems unreadable in decimal and I'm wondering whether it's
> the best value to use to identify the domain. Does this system have over 1
> million L3 domains?
> 
> Thanks!
> -Peter