lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <4e5da8a3-ce86-405c-b480-66cc1a6bbcd5@vivo.com>
Date:   Thu, 9 Nov 2023 16:30:42 +0800
From:   zhiguojiang <justinjiang@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        opensource.kernel@...o.com
Subject: Re: [PATCH] mm:ALLOC_HIGHATOMIC flag allocation issuse



在 2023/11/9 5:57, Andrew Morton 写道:
> On Wed,  8 Nov 2023 14:54:07 +0800 Zhiguo Jiang <justinjiang@...o.com> wrote:
Hi Andrew Morton :

In response to your three good suggestions, I have made relevant 
modifications in [PATCH v2 1/1], thanks for your review.
https://lore.kernel.org/all/20231109073133.792-2-justinjiang@vivo.com/

>> In case that alloc_flags contains ALLOC_HIGHATOMIC and alloc order
>> is order1/2/3/10 in rmqueue(), if pages are alloced successfully
>> from pcplist, a free pageblock will be also moved from the alloced
>> migratetype freelist to MIGRATE_HIGHATOMIC freelist, rather than
>> alloc from MIGRATE_HIGHATOMIC freelist firstly, so this will result
>> in an increasing number of pages on the MIGRATE_HIGHATOMIC freelist,
>> pages in other migratetype freelist are reduced and more likely to
>> allocation failure.
>>
>> Currently the sequence of ALLOC_HIGHATOMIC allocation is:
>> pcplist --> rmqueue_bulk() --> rmqueue_buddy() MIGRATE_HIGHATOMIC
>> --> rmqueue_buddy() allocation migratetype.
>>
>> Due to the fact that requesting pages from the pcplist is faster than
>> buddy, the sequence of modifying the ALLOC_HIGHATOMIC allocation is:
>> pcplist --> rmqueue_buddy() MIGRATE_HIGHATOMIC --> rmqueue_buddy()
>> allocation migratetype.
>>
>> This patch can solve the failure problem of allocating other types of
>> pages due to excessive MIGRATE_HIGHATOMIC freelist reservations.
>>
>> In comparative testing, cat /proc/pagetypeinfo and the HighAtomic
>> freelist size is:
>> Test without this patch:
>> Node 0, zone Normal, type HighAtomic 2369 771 138 15 0 0 0 0 0 0 0
>> Test with this patch:
>> Node 0, zone Normal, type HighAtomic 206 82 4 2 1 0 0 0 0 0 0
> Hopefully hannes can check this for us, but I have a stylistic concern...
>
>> +#define ALLOC_PCPLIST		0x1000 /* Allocations from pcplist */
>>   
>>   /* Flags that allow allocations below the min watermark. */
>>   #define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index b8544f08cc36..67cec88164b1
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2854,11 +2854,15 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
>>   			int batch = nr_pcp_alloc(pcp, zone, order);
>>   			int alloced;
>>   
>> +			if (alloc_flags & ALLOC_HIGHATOMIC)
>> +				goto out;
>> +
> A comment here explaining why we're doing this would help readers.
add in [PATCH v2 1/1].
>
>>   			alloced = rmqueue_bulk(zone, order,
>>   					batch, list,
>>   					migratetype, alloc_flags);
>>   
>>   			pcp->count += alloced << order;
>> +out:
>>   			if (unlikely(list_empty(list)))
>>   				return NULL;
>>   		}
>> @@ -2921,7 +2925,7 @@ __no_sanitize_memory
>>   static inline
>>   struct page *rmqueue(struct zone *preferred_zone,
>>   			struct zone *zone, unsigned int order,
>> -			gfp_t gfp_flags, unsigned int alloc_flags,
>> +			gfp_t gfp_flags, unsigned int *alloc_flags,
>>   			int migratetype)
>>   {
>>   	struct page *page;
>> @@ -2934,17 +2938,19 @@ struct page *rmqueue(struct zone *preferred_zone,
>>   
>>   	if (likely(pcp_allowed_order(order))) {
>>   		page = rmqueue_pcplist(preferred_zone, zone, order,
>> -				       migratetype, alloc_flags);
>> -		if (likely(page))
>> +				       migratetype, *alloc_flags);
>> +		if (likely(page)) {
>> +			*alloc_flags |= ALLOC_PCPLIST;
>>   			goto out;
>> +		}
>>   	}
> So we're effectively returning a boolean to the caller via *alloc_flags.
>
> This isn't a great way of doing it.  Wouldn't it be cleaner to pass a
> new bool* argument to rmqueue() for this?  Make it explicit?
>
> rmqueue() will be inlined into its sole caller, so this approach
> shouldn't add overhead.
Yes,I agree with your suggestion that pass a new bool* argument to 
rmqueue() for this, it is more clearer.
I have modified in [PATCH v2 1/1].
>
>> -	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
>> +	page = rmqueue_buddy(preferred_zone, zone, order, *alloc_flags,
>>   							migratetype);
>>
>>   out:
>>   	/* Separate test+clear to avoid unnecessary atomics */
>> -	if ((alloc_flags & ALLOC_KSWAPD) &&
>> +	if ((*alloc_flags & ALLOC_KSWAPD) &&
>>   	    unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
>>   		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
>>   		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
>> @@ -3343,7 +3349,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>>   
>>   try_this_zone:
>>   		page = rmqueue(ac->preferred_zoneref->zone, zone, order,
>> -				gfp_mask, alloc_flags, ac->migratetype);
>> +				gfp_mask, &alloc_flags, ac->migratetype);
>>   		if (page) {
>>   			prep_new_page(page, order, gfp_mask, alloc_flags);
>>   
>> @@ -3351,7 +3357,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>>   			 * If this is a high-order atomic allocation then check
>>   			 * if the pageblock should be reserved for the future
>>   			 */
>> -			if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
>> +			if (unlikely(alloc_flags & ALLOC_HIGHATOMIC) &&
>> +				unlikely(!(alloc_flags & ALLOC_PCPLIST)))
> Again, a comment explaining the reason for the test would be good.
add in [PATCH v2 1/1].
>
>>   				reserve_highatomic_pageblock(page, zone);
>>   
>>   			return page;
>> -- 
>> 2.39.0
>>

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ