From: James Morse <james.morse@arm.com>
To: Reinette Chatre <reinette.chatre@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, Babu Moger <Babu.Moger@amd.com>,
shameerali.kolothum.thodi@huawei.com,
Jamie Iles <jamie@nuviainc.com>,
D Scott Phillips OS <scott@os.amperecomputing.com>,
lcherian@marvell.com, bobo.shaobowang@huawei.com,
tan.shaopeng@fujitsu.com
Subject: Re: [PATCH v3 12/21] x86/resctrl: Calculate bandwidth from the previous __mon_event_count() chunks
Date: Wed, 30 Mar 2022 17:44:10 +0100 [thread overview]
Message-ID: <146a1a64-7925-008f-a817-fe0860b30105@arm.com> (raw)
In-Reply-To: <c4088205-a344-5ef8-15e2-9ccc5d1691ea@intel.com>
Hi Reinette,
On 05/03/2022 00:27, Reinette Chatre wrote:
> On 2/17/2022 10:21 AM, James Morse wrote:
>> mbm_bw_count() is only called by the mbm_handle_overflow() worker once a
>> second. It reads the hardware register, calculates the bandwidth and
>> updates m->prev_bw_msr which is used to hold the previous hardware register
>> value.
>>
>> Operating directly on hardware register values makes it difficult to make
>> this code architecture independent, so that it can be moved to /fs/,
>> making the mba_sc feature something resctrl supports with no additional
>> support from the architecture.
>> Prior to calling mbm_bw_count(), mbm_update() reads from the same hardware
>> register using __mon_event_count().
>>
>> Change mbm_bw_count() to use the current chunks value most recently saved by
>> __mon_event_count(). This removes an extra call to __rmid_read().
>
>> Instead of using m->prev_msr to calculate the number of chunks seen,
>> use the rr->val that was updated by __mon_event_count(). This removes a extra
>> calls to mbm_overflow_count() and get_corrected_mbm_count().
>
> "removes a extra calls" -> "removes an extra call" ?
>
> __mon_event_count() ends with "rr->val += get_corrected_mbm_count()" and
> it is called twice by mbm_update(). The intention in this change is for
> mbm_bw_count() to benefit from the rmid read done just before ...
> but would using rr->val within mbm_bw_count() not result in it getting
> data from both rmid reads due to the increment?
Yes, bother. I thought those were mutually exclusive, but its __mon_event_count() that
uses a different struct mbm_state for each set of raw values, not mbm_update().
[...]
> Should rr.val perhaps be reset before each __mon_event_count() call instead of
> just at the beginning of mbm_update()?
Yes. This is because the struct rmid_read is just to allow __mon_event_count() to do its
thing, nothing used to read those values.
>> Calculating bandwidth like this means mbm_bw_count() no longer operates
>> on hardware register values directly.
Thanks!
James
next prev parent reply other threads:[~2022-03-30 16:44 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-17 18:20 [PATCH v3 00/21] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse
2022-02-17 18:20 ` [PATCH v3 01/21] x86/resctrl: Kill off alloc_enabled James Morse
2022-03-16 21:48 ` Reinette Chatre
2022-02-17 18:20 ` [PATCH v3 02/21] x86/resctrl: Merge mon_capable and mon_enabled James Morse
2022-02-17 18:20 ` [PATCH v3 03/21] x86/resctrl: Add domain online callback for resctrl work James Morse
2022-02-17 18:20 ` [PATCH v3 04/21] x86/resctrl: Group struct rdt_hw_domain cleanup James Morse
2022-02-17 18:20 ` [PATCH v3 05/21] x86/resctrl: Add domain offline callback for resctrl work James Morse
2022-02-17 18:20 ` [PATCH v3 06/21] x86/resctrl: Remove set_mba_sc()s control array re-initialisation James Morse
2022-02-17 18:20 ` [PATCH v3 07/21] x86/resctrl: Create mba_sc configuration in the rdt_domain James Morse
2022-03-05 0:26 ` Reinette Chatre
2022-03-30 16:43 ` James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-03-30 16:43 ` James Morse
2022-04-01 22:54 ` Reinette Chatre
2022-04-04 16:35 ` James Morse
2022-04-04 20:43 ` Reinette Chatre
2022-02-17 18:20 ` [PATCH v3 08/21] x86/resctrl: Switch over to the resctrl mbps_val list James Morse
2022-02-17 18:20 ` [PATCH v3 09/21] x86/resctrl: Remove architecture copy of mbps_val James Morse
2022-02-17 18:20 ` [PATCH v3 10/21] x86/resctrl: Abstract and use supports_mba_mbps() James Morse
2022-02-17 18:21 ` [PATCH v3 11/21] x86/resctrl: Allow update_mba_bw() to update controls directly James Morse
2022-02-17 18:21 ` [PATCH v3 12/21] x86/resctrl: Calculate bandwidth from the previous __mon_event_count() chunks James Morse
2022-03-05 0:27 ` Reinette Chatre
2022-03-30 16:44 ` James Morse [this message]
2022-02-17 18:21 ` [PATCH v3 13/21] x86/recstrl: Add per-rmid arch private storage for overflow and chunks James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 14/21] x86/recstrl: Allow per-rmid arch private storage to be reset James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 15/21] x86/resctrl: Abstract __rmid_read() James Morse
2022-03-16 21:52 ` Reinette Chatre
2022-03-30 16:44 ` James Morse
2022-02-17 18:21 ` [PATCH v3 16/21] x86/resctrl: Pass the required parameters into resctrl_arch_rmid_read() James Morse
2022-03-23 20:58 ` Rob Herring
2022-03-30 16:45 ` James Morse
2022-02-17 18:21 ` [PATCH v3 17/21] x86/resctrl: Move mbm_overflow_count() " James Morse
2022-02-17 18:21 ` [PATCH v3 18/21] x86/resctrl: Move get_corrected_mbm_count() " James Morse
2022-02-17 18:21 ` [PATCH v3 19/21] x86/resctrl: Rename and change the units of resctrl_cqm_threshold James Morse
2022-03-17 17:00 ` Reinette Chatre
2022-03-30 16:45 ` James Morse
2022-04-01 22:55 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 20/21] x86/resctrl: Add resctrl_rmid_realloc_limit to abstract x86's boot_cpu_data James Morse
2022-02-17 18:21 ` [PATCH v3 21/21] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse
2022-03-23 21:17 ` Rob Herring
2022-04-04 16:36 ` James Morse
2022-03-07 12:56 ` [PATCH v3 00/21] " Jamie Iles
2022-04-04 16:36 ` James Morse
2022-03-15 6:41 ` Xin Hao
2022-04-04 16:36 ` James Morse
2022-03-15 8:16 ` tan.shaopeng
2022-04-04 16:35 ` James Morse
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