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From: Christopher Lameter <cl@linux.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Matthew Wilcox <willy@infradead.org>,
	Pekka Enberg <penberg@kernel.org>,
	linux-mm@kvack.org, dm-devel@redhat.com,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND] slab: introduce the flag SLAB_MINIMIZE_WASTE
Date: Wed, 18 Apr 2018 09:55:31 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1804180952580.1334@nuc-kabylake> (raw)
In-Reply-To: <alpine.LRH.2.02.1804171454020.26973@file01.intranet.prod.int.rdu2.redhat.com>

On Tue, 17 Apr 2018, Mikulas Patocka wrote:

> I can make a slub-only patch with no extra flag (on a freshly booted
> system it increases only the order of caches "TCPv6" and "sighand_cache"
> by one - so it should not have unexpected effects):
>
> Doing a generic solution for slab would be more comlpicated because slab
> assumes that all slabs have the same order, so it can't fall-back to
> lower-order allocations.

Well again SLAB uses compound pages and thus would be able to detect the
size of the page. It may be some work but it could be done.

>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2018-04-17 19:59:49.000000000 +0200
> +++ linux-2.6/mm/slub.c	2018-04-17 20:58:23.000000000 +0200
> @@ -3252,6 +3252,7 @@ static inline unsigned int slab_order(un
>  static inline int calculate_order(unsigned int size, unsigned int reserved)
>  {
>  	unsigned int order;
> +	unsigned int test_order;
>  	unsigned int min_objects;
>  	unsigned int max_objects;
>
> @@ -3277,7 +3278,7 @@ static inline int calculate_order(unsign
>  			order = slab_order(size, min_objects,
>  					slub_max_order, fraction, reserved);
>  			if (order <= slub_max_order)
> -				return order;
> +				goto ret_order;
>  			fraction /= 2;
>  		}
>  		min_objects--;
> @@ -3289,15 +3290,25 @@ static inline int calculate_order(unsign
>  	 */
>  	order = slab_order(size, 1, slub_max_order, 1, reserved);

The slab order is determined in slab_order()

>  	if (order <= slub_max_order)
> -		return order;
> +		goto ret_order;
>
>  	/*
>  	 * Doh this slab cannot be placed using slub_max_order.
>  	 */
>  	order = slab_order(size, 1, MAX_ORDER, 1, reserved);
> -	if (order < MAX_ORDER)
> -		return order;
> -	return -ENOSYS;
> +	if (order >= MAX_ORDER)
> +		return -ENOSYS;
> +
> +ret_order:
> +	for (test_order = order + 1; test_order < MAX_ORDER; test_order++) {
> +		unsigned long order_objects = ((PAGE_SIZE << order) - reserved) / size;
> +		unsigned long test_order_objects = ((PAGE_SIZE << test_order) - reserved) / size;
> +		if (test_order_objects > min(32, MAX_OBJS_PER_PAGE))
> +			break;
> +		if (test_order_objects > order_objects << (test_order - order))
> +			order = test_order;
> +	}
> +	return order;

Could yo move that logic into slab_order()? It does something awfully
similar.

  reply	other threads:[~2018-04-18 14:55 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <alpine.LRH.2.02.1803201740280.21066@file01.intranet.prod.int.rdu2.redhat.com>
     [not found] ` <alpine.DEB.2.20.1803211024220.2175@nuc-kabylake>
     [not found]   ` <alpine.LRH.2.02.1803211153320.16017@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]     ` <alpine.DEB.2.20.1803211226350.3174@nuc-kabylake>
     [not found]       ` <alpine.LRH.2.02.1803211425330.26409@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]         ` <20c58a03-90a8-7e75-5fc7-856facfb6c8a@suse.cz>
     [not found]           ` <20180413151019.GA5660@redhat.com>
     [not found]             ` <ee8807ff-d650-0064-70bf-e1d77fa61f5c@suse.cz>
     [not found]               ` <20180416142703.GA22422@redhat.com>
     [not found]                 ` <alpine.LRH.2.02.1804161031300.24222@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                   ` <20180416144638.GA22484@redhat.com>
2018-04-16 19:32                     ` Mikulas Patocka
2018-04-17 14:45                       ` Christopher Lameter
2018-04-17 16:16                         ` Vlastimil Babka
2018-04-17 16:38                           ` Christopher Lameter
2018-04-17 19:09                             ` Mikulas Patocka
2018-04-17 17:26                           ` Mikulas Patocka
2018-04-17 19:13                             ` Vlastimil Babka
2018-04-17 19:06                         ` Mikulas Patocka
2018-04-18 14:55                           ` Christopher Lameter [this message]
2018-04-25 21:04                             ` Mikulas Patocka
2018-04-25 23:24                               ` Mikulas Patocka
2018-04-26 19:01                                 ` Christopher Lameter
2018-04-26 21:09                                   ` Mikulas Patocka
2018-04-27 16:41                                     ` Christopher Lameter
2018-04-27 19:19                                       ` Mikulas Patocka
2018-06-13 17:01                                         ` Mikulas Patocka
2018-06-13 18:16                                           ` Christoph Hellwig
2018-06-13 18:53                                             ` Mikulas Patocka
2018-04-26 18:51                               ` Christopher Lameter
     [not found]                     ` <alpine.LRH.2.02.1804161054410.17807@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                       ` <alpine.DEB.2.20.1804161018030.9397@nuc-kabylake>
     [not found]                         ` <alpine.LRH.2.02.1804161123400.17807@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                           ` <alpine.DEB.2.20.1804161043430.9622@nuc-kabylake>
     [not found]                             ` <alpine.LRH.2.02.1804161532480.19492@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                               ` <b0e6ccf6-06ce-e50b-840e-c8d3072382fd@suse.cz>
2018-04-16 21:01                                 ` Mikulas Patocka
2018-04-17 14:40                                   ` Christopher Lameter
2018-04-17 18:53                                     ` Mikulas Patocka
2018-04-17 21:42                                       ` Christopher Lameter

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