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Date: Wed, 17 Apr 2019 04:51:18 +0800
From: Xiaochen Shen <xiaochen.shen@...el.com>
To: Borislav Petkov <bp@...en8.de>
Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
tony.luck@...el.com, fenghua.yu@...el.com,
reinette.chatre@...el.com, x86@...nel.org,
linux-kernel@...r.kernel.org, pei.p.jia@...el.com,
xiaochen.shen@...el.com
Subject: Re: [PATCH 2/2] x86/resctrl: Initialize new resource group with
default MBA values
Hi Boris,
Thank you very much for code review.
I will fix these issues in v2 patch.
Please find more comments inline.
Thank you.
On 4/15/2019 19:34, Borislav Petkov wrote:
> On Wed, Apr 10, 2019 at 03:55:28AM +0800, Xiaochen Shen wrote:
>> Currently when a new resource group is created, the allocation values
>> of MBA resource are not initialized and remain meaningless data.
>>
>> For example:
>> mkdir /sys/fs/resctrl/p1
>> cat /sys/fs/resctrl/p1/schemata
>> MB:0=100;1=100
>>
>> echo "MB:0=10;1=20" > /sys/fs/resctrl/p1/schemata
>> cat /sys/fs/resctrl/p1/schemata
>> MB:0= 10;1= 20
>>
>> rmdir /sys/fs/resctrl/p1
>> mkdir /sys/fs/resctrl/p2
>> cat /sys/fs/resctrl/p2/schemata
>> MB:0= 10;1= 20
>>
>> When the new group is created, it is reasonable to initialize MBA
>> resource with default values.
>>
>> Initialize MBA resource and cache resources in separate functions.
>
> Please format your commit message by indenting the examples:
OK. Thank you.
>
> x86/resctrl: Initialize a new resource group with default MBA values
>
> Currently, when a new resource group is created, the allocation values
> of the MBA resource are not initialized and remain meaningless data.
>
> For example:
>
> mkdir /sys/fs/resctrl/p1
> cat /sys/fs/resctrl/p1/schemata
> MB:0=100;1=100
>
> echo "MB:0=10;1=20" > /sys/fs/resctrl/p1/schemata
> cat /sys/fs/resctrl/p1/schemata
> MB:0= 10;1= 20
>
> rmdir /sys/fs/resctrl/p1
> mkdir /sys/fs/resctrl/p2
> cat /sys/fs/resctrl/p2/schemata
> MB:0= 10;1= 20
>
> Therefore, when the new group is created, it is reasonable to initialize
> MBA resource with default values.
>
> Initialize the MBA resource and cache resources in separate functions."
>
> Thx.
>
>>
>> Signed-off-by: Xiaochen Shen <xiaochen.shen@...el.com>
>> Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 +-
>> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 139 ++++++++++++++++--------------
>> 2 files changed, 75 insertions(+), 68 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> index 2dbd990..576bb6a 100644
>> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> @@ -342,10 +342,10 @@ int update_domains(struct rdt_resource *r, int closid)
>> if (cpumask_empty(cpu_mask) || mba_sc)
>> goto done;
>> cpu = get_cpu();
>> - /* Update CBM on this cpu if it's in cpu_mask. */
>> + /* Update resource control msr on this cpu if it's in cpu_mask. */
>
> s/cpu/CPU/g
>
OK.
>> if (cpumask_test_cpu(cpu, cpu_mask))
>> rdt_ctrl_update(&msr_param);
>> - /* Update CBM on other cpus. */
>> + /* Update resource control msr on other cpus. */
>
> Ditto.
OK.
>
>> smp_call_function_many(cpu_mask, rdt_ctrl_update, &msr_param, 1);
>> put_cpu();
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 08e0333..9f12a02 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -2516,8 +2516,8 @@ static void cbm_ensure_valid(u32 *_val, struct rdt_resource *r)
>> bitmap_clear(val, zero_bit, cbm_len - zero_bit);
>> }
>>
>> -/**
>> - * rdtgroup_init_alloc - Initialize the new RDT group's allocations
>> +/*
>> + * Initialize cache resources with default values.
>> *
>> * A new RDT group is being created on an allocation capable (CAT)
>> * supporting system. Set this group up to start off with all usable
>> @@ -2526,85 +2526,92 @@ static void cbm_ensure_valid(u32 *_val, struct rdt_resource *r)
>> * All-zero CBM is invalid. If there are no more shareable bits available
>> * on any domain then the entire allocation will fail.
>> */
>> -static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
>> +static int rdtgroup_init_cat(struct rdt_resource *r, u32 closid)
>> {
>> struct rdt_resource *r_cdp = NULL;
>> struct rdt_domain *d_cdp = NULL;
>> u32 used_b = 0, unused_b = 0;
>> - u32 closid = rdtgrp->closid;
>> - struct rdt_resource *r;
>> unsigned long tmp_cbm;
>> enum rdtgrp_mode mode;
>> struct rdt_domain *d;
>> u32 peer_ctl, *ctrl;
>> - int i, ret;
>> + int i;
>>
>> - for_each_alloc_enabled_rdt_resource(r) {
>> + list_for_each_entry(d, &r->domains, list) {
>> + rdt_cdp_peer_get(r, d, &r_cdp, &d_cdp);
>> + d->have_new_ctrl = false;
>> + d->new_ctrl = r->cache.shareable_bits;
>> + used_b = r->cache.shareable_bits;
>> + ctrl = d->ctrl_val;
>> + for (i = 0; i < closids_supported(); i++, ctrl++) {
>> + if (closid_allocated(i) && i != closid) {
>> + mode = rdtgroup_mode_by_closid(i);
>> + if (mode == RDT_MODE_PSEUDO_LOCKSETUP)
>> + break;
>> + /*
>> + * If CDP is active include peer
>> + * domain's usage to ensure there
>> + * is no overlap with an exclusive
>> + * group.
>> + */
>> + if (d_cdp)
>> + peer_ctl = d_cdp->ctrl_val[i];
>> + else
>> + peer_ctl = 0;
>> + used_b |= *ctrl | peer_ctl;
>> + if (mode == RDT_MODE_SHAREABLE)
>> + d->new_ctrl |= *ctrl | peer_ctl;
>> + }
>> + }
>> + if (d->plr && d->plr->cbm > 0)
>> + used_b |= d->plr->cbm;
>> + unused_b = used_b ^ (BIT_MASK(r->cache.cbm_len) - 1);
>> + unused_b &= BIT_MASK(r->cache.cbm_len) - 1;
>> + d->new_ctrl |= unused_b;
>> + cbm_ensure_valid(&d->new_ctrl, r);
>> /*
>> - * Only initialize default allocations for CBM cache
>> - * resources
>> + * Assign the u32 CBM to an unsigned long to ensure
>> + * that bitmap_weight() does not access out-of-bound
>> + * memory.
>> */
>
> So all this code working on a rdt_domain *d pointer could be carved out
> into a separate function called something like:
>
> __init_one_rdt_domain(d, ...)
>
> and this will make the code more readable and save us at least 2
> indentation levels.
>
> Please do that in a preparatory patch.
Good suggestion. I will do it in v2 patch.
>
>> - if (r->rid == RDT_RESOURCE_MBA)
>> - continue;
>
> Then, after having done that, it would be very obvious when you do this
> above because you won't be calling that __init_one_rdt_domain() function
> for an MBA anyway. >
> Thx.
>
In this patch we initialize MBA resource and cache resources in separate
functions rdtgroup_init_cat() and rdtgroup_init_mba(). If
__init_one_rdt_domain() is only called by rdtgroup_init_cat(), how about
using function name "__init_one_rdt_domain_cat()"?
Thank you.
Best regards,
Xiaochen
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