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

[Rex Nie]

> -----邮件原件-----
> 发件人: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> 发送时间: 2024年3月15日 8:52
> 收件人: Peter Newman <peternewman@xxxxxxxxxx>; 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
> 主题: Re: 32bit resctrl? (was Re: [PATCH v2] fs/resctrl: fix domid loss precision
> issue)
> 
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> 
> On 3/14/2024 5:04 PM, Peter Newman wrote:
> > 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?
> 
> I propose that Rex includes the information about Arm's cache IDs [1] in future
> changelogs.
> 
> Reinette
> 
OK, I will include the link.

Rex

> 
> [1]
> https://lore.kernel.org/lkml/KL1PR0601MB577303C9D0B1247436BB06F8E62
> 42@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/