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

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Date: Fri, 15 Mar 2024 01:21:40 +0000
From: Rex Nie <rex.nie@...uarmicro.com>
To: Reinette Chatre <reinette.chatre@...el.com>, Peter Newman
	<peternewman@...gle.com>
CC: "james.morse@....com" <james.morse@....com>, "x86@...nel.org"
	<x86@...nel.org>, "Luck, Tony" <tony.luck@...el.com>, Babu Moger
	<babu.moger@....com>, Borislav Petkov <bp@...en8.de>, "fenghua.yu@...el.com"
	<fenghua.yu@...el.com>, "ilpo.jarvinen@...ux.intel.com"
	<ilpo.jarvinen@...ux.intel.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject:
 答复: 32bit resctrl? (was Re: [PATCH v2] fs/resctrl: fix domid loss precision issue)



> -----邮件原件-----
> 发件人: Reinette Chatre <reinette.chatre@...el.com>
> 发送时间: 2024年3月15日 8:52
> 收件人: Peter Newman <peternewman@...gle.com>; Rex Nie
> <rex.nie@...uarmicro.com>
> 抄送: james.morse@....com; x86@...nel.org; Luck, Tony
> <tony.luck@...el.com>; Babu Moger <babu.moger@....com>; Borislav
> Petkov <bp@...en8.de>; fenghua.yu@...el.com; ilpo.jarvinen@...ux.intel.com;
> linux-kernel@...r.kernel.org
> 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.
> 
> 
> On 3/14/2024 5:04 PM, Peter Newman wrote:
> > On Thu, Mar 14, 2024 at 8:25 AM Reinette Chatre
> > <reinette.chatre@...el.com> 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@...PR0601MB5773.apcprd06.prod.outlook.com/