linux-kernel - Re: [PATCH v13 11/14] x86/sgx: Abstract check for global reclaimable pages

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Date: Mon, 06 May 2024 13:00:46 -0500
From: "Haitao Huang" <haitao.huang@...ux.intel.com>
To: jarkko@...nel.org, dave.hansen@...ux.intel.com, tj@...nel.org,
 mkoutny@...e.com, linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
 x86@...nel.org, cgroups@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, hpa@...or.com, sohil.mehta@...el.com,
 tim.c.chen@...ux.intel.com, "Huang, Kai" <kai.huang@...el.com>
Cc: zhiquan1.li@...el.com, kristen@...ux.intel.com, seanjc@...gle.com,
 zhanb@...rosoft.com, anakrish@...rosoft.com, mikko.ylinen@...ux.intel.com,
 yangjie@...rosoft.com, chrisyan@...rosoft.com
Subject: Re: [PATCH v13 11/14] x86/sgx: Abstract check for global reclaimable
 pages

Hi Kai
Sorry there seems to be some delay in receiving my emails.

On Thu, 02 May 2024 18:23:06 -0500, Huang, Kai <kai.huang@...el.com> wrote:

>
>
> On 1/05/2024 7:51 am, Haitao Huang wrote:
>> From: Kristen Carlson Accardi <kristen@...ux.intel.com>
>>  For the global reclaimer to determine if any page available for
>> reclamation at the global level, it currently only checks for emptiness
>> of the global LRU. That will be inadequate when pages are tracked in
>> multiple LRUs, one per cgroup. For this purpose, create a new helper,
>> sgx_can_reclaim_global(), to abstract this check. Currently it only
>> checks the global LRU, later will check emptiness of LRUs of all cgroups
>> when per-cgroup tracking is turned on.
>>  Replace all the checks for emptiness of the global LRU,
>> list_empty(&sgx_global_lru.reclaimable), with calls to
>> sgx_can_reclaim_global().
>>  Rename sgx_should_reclaim() to sgx_should_reclaim_global() as it is  
>> used
>> to check if a global reclamation should be performed.
>>  Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com>
>> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
>> Co-developed-by: Haitao Huang <haitao.huang@...ux.intel.com>
>> Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
>> Tested-by: Jarkko Sakkinen <jarkko@...nel.org>
>> ---
>
> Free free to add:
>
> Reviewed-by: Kai Huang <kai.huang@...el.com>
>

Thanks

> One thing below:
>
> [...]
>
>> -static bool sgx_should_reclaim(unsigned long watermark)
>> +static bool sgx_should_reclaim_global(unsigned long watermark)
>>   {
>>   	return atomic_long_read(&sgx_nr_free_pages) < watermark &&
>> -	       !list_empty(&sgx_global_lru.reclaimable);
>> +		sgx_can_reclaim_global();
>>   }
>>     static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
>> @@ -405,7 +413,7 @@ static void sgx_reclaim_pages_global(struct  
>> mm_struct *charge_mm)
>>    */
>>   void sgx_reclaim_direct(void)
>>   {
>> -	if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
>> +	if (sgx_should_reclaim_global(SGX_NR_LOW_PAGES))
>>   		sgx_reclaim_pages_global(current->mm);
>>   }
>>
>
> Hmm.. Sorry for not pointing out in the previous version.
>
> Perhaps it makes more sense to do the rename in the patch ...
>
>    x86/sgx: Add basic EPC reclamation flow for cgroup
>
> ... where we have actually introduced the concept of per-cgroup reclaim,  
> and we literally have below change in that patch:
>
>   void sgx_reclaim_direct(void)
>   {
>   	if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
> -		sgx_reclaim_pages();
> +		sgx_reclaim_pages_global();
>   }
>
> So in that patch, the sgx_should_reclaim() literally just means we  
> should do gloabl reclaim, but not the per-cgruop reclaim.  Thus, perhaps  
> we just do the renaming here together with the new  
> sgx_reclaim_pages_global().
>
> If there's a new version needed, please move the renaming to that patch?
>
Will do

BR
Haitao