linux-kernel - Re: 答复: [PATCH v4] mm/compaction: let proactive compaction order configurable

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Date:   Tue, 15 Jun 2021 10:04:36 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Chu,Kaiping" <chukaiping@...du.com>,
        "mcgrof@...nel.org" <mcgrof@...nel.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "yzaikin@...gle.com" <yzaikin@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "nigupta@...dia.com" <nigupta@...dia.com>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "khalid.aziz@...cle.com" <khalid.aziz@...cle.com>,
        "iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
        "mateusznosek0@...il.com" <mateusznosek0@...il.com>,
        "sh_def@....com" <sh_def@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: 答复: [PATCH v4] mm/compaction: let proactive compaction order configurable

On 15.06.21 03:11, Chu,Kaiping wrote:
> 
> 
>> -----邮件原件-----
>> 发件人: David Hildenbrand <david@...hat.com>
>> 发送时间: 2021年6月9日 18:45
>> 收件人: Chu,Kaiping <chukaiping@...du.com>; mcgrof@...nel.org;
>> keescook@...omium.org; yzaikin@...gle.com; akpm@...ux-foundation.org;
>> vbabka@...e.cz; nigupta@...dia.com; bhe@...hat.com;
>> khalid.aziz@...cle.com; iamjoonsoo.kim@....com;
>> mateusznosek0@...il.com; sh_def@....com
>> 抄送: linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org;
>> linux-mm@...ck.org
>> 主题: Re: [PATCH v4] mm/compaction: let proactive compaction order
>> configurable
>>
>> On 28.04.21 04:28, chukaiping wrote:
>>> Currently the proactive compaction order is fixed to
>>> COMPACTION_HPAGE_ORDER(9), it's OK in most machines with lots of
>>> normal 4KB memory, but it's too high for the machines with small
>>> normal memory, for example the machines with most memory configured as
>>> 1GB hugetlbfs huge pages. In these machines the max order of free
>>> pages is often below 9, and it's always below 9 even with hard
>>> compaction. This will lead to proactive compaction be triggered very
>>> frequently. In these machines we only care about order of 3 or 4.
>>> This patch export the oder to proc and let it configurable by user,
>>> and the default value is still COMPACTION_HPAGE_ORDER.
>>>
>>> Signed-off-by: chukaiping <chukaiping@...du.com>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> ---
>>>
>>> Changes in v4:
>>>       - change the sysctl file name to proactive_compation_order
>>>
>>> Changes in v3:
>>>       - change the min value of compaction_order to 1 because the
>> fragmentation
>>>         index of order 0 is always 0
>>>       - move the definition of max_buddy_zone into #ifdef
>>> CONFIG_COMPACTION
>>>
>>> Changes in v2:
>>>       - fix the compile error in ia64 and powerpc, move the initialization
>>>         of sysctl_compaction_order to kcompactd_init because
>>>         COMPACTION_HPAGE_ORDER is a variable in these architectures
>>>       - change the hard coded max order number from 10 to MAX_ORDER -
>> 1
>>>
>>>    include/linux/compaction.h |    1 +
>>>    kernel/sysctl.c            |   10 ++++++++++
>>>    mm/compaction.c            |   12 ++++++++----
>>>    3 files changed, 19 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
>>> index ed4070e..a0226b1 100644
>>> --- a/include/linux/compaction.h
>>> +++ b/include/linux/compaction.h
>>> @@ -83,6 +83,7 @@ static inline unsigned long compact_gap(unsigned int
>> order)
>>>    #ifdef CONFIG_COMPACTION
>>>    extern int sysctl_compact_memory;
>>>    extern unsigned int sysctl_compaction_proactiveness;
>>> +extern unsigned int sysctl_proactive_compaction_order;
>>>    extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>>>    			void *buffer, size_t *length, loff_t *ppos);
>>>    extern int sysctl_extfrag_threshold; diff --git a/kernel/sysctl.c
>>> b/kernel/sysctl.c index 62fbd09..ed9012e 100644
>>> --- a/kernel/sysctl.c
>>> +++ b/kernel/sysctl.c
>>> @@ -196,6 +196,7 @@ enum sysctl_writes_mode {
>>>    #endif /* CONFIG_SCHED_DEBUG */
>>>
>>>    #ifdef CONFIG_COMPACTION
>>> +static int max_buddy_zone = MAX_ORDER - 1;
>>>    static int min_extfrag_threshold;
>>>    static int max_extfrag_threshold = 1000;
>>>    #endif
>>> @@ -2871,6 +2872,15 @@ int proc_do_static_key(struct ctl_table *table,
>> int write,
>>>    		.extra2		= &one_hundred,
>>>    	},
>>>    	{
>>> +		.procname       = "proactive_compation_order",
>>> +		.data           = &sysctl_proactive_compaction_order,
>>> +		.maxlen         = sizeof(sysctl_proactive_compaction_order),
>>> +		.mode           = 0644,
>>> +		.proc_handler   = proc_dointvec_minmax,
>>> +		.extra1         = SYSCTL_ONE,
>>> +		.extra2         = &max_buddy_zone,
>>> +	},
>>> +	{
>>>    		.procname	= "extfrag_threshold",
>>>    		.data		= &sysctl_extfrag_threshold,
>>>    		.maxlen		= sizeof(int),
>>> diff --git a/mm/compaction.c b/mm/compaction.c index e04f447..171436e
>>> 100644
>>> --- a/mm/compaction.c
>>> +++ b/mm/compaction.c
>>> @@ -1925,17 +1925,18 @@ static bool kswapd_is_running(pg_data_t
>>> *pgdat)
>>>
>>>    /*
>>>     * A zone's fragmentation score is the external fragmentation wrt to
>>> the
>>> - * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100].
>>> + * sysctl_proactive_compaction_order. It returns a value in the range
>>> + * [0, 100].
>>>     */
>>>    static unsigned int fragmentation_score_zone(struct zone *zone)
>>>    {
>>> -	return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER);
>>> +	return extfrag_for_order(zone, sysctl_proactive_compaction_order);
>>>    }
>>>
>>>    /*
>>>     * A weighted zone's fragmentation score is the external
>>> fragmentation
>>> - * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It
>>> - * returns a value in the range [0, 100].
>>> + * wrt to the sysctl_proactive_compaction_order scaled by the zone's size.
>>> + * It returns a value in the range [0, 100].
>>>     *
>>>     * The scaling factor ensures that proactive compaction focuses on larger
>>>     * zones like ZONE_NORMAL, rather than smaller, specialized zones
>>> like @@ -2666,6 +2667,7 @@ static void compact_nodes(void)
>>>     * background. It takes values in the range [0, 100].
>>>     */
>>>    unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
>>> +unsigned int __read_mostly sysctl_proactive_compaction_order;
>>>
>>>    /*
>>>     * This is the entry point for compacting all nodes via @@ -2958,6
>>> +2960,8 @@ static int __init kcompactd_init(void)
>>>    	int nid;
>>>    	int ret;
>>>
>>> +	sysctl_proactive_compaction_order = COMPACTION_HPAGE_ORDER;
>>> +
>>>    	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
>>>    					"mm/compaction:online",
>>>    					kcompactd_cpu_online, NULL);
>>>
>>
>> Hm, do we actually want to put an upper limit to the order a user can supply?
> No，we should allow user to configure the order from 1 to MAX_ORDER - 1.

Ah, I missed that we enforce an upper limit of "MAX_ORDER - 1" -- thanks.


-- 
Thanks,

David / dhildenb