From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4642C6A2.1090809@yahoo.com.au> Date: Thu, 10 May 2007 17:15:46 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: [patch] slob: implement RCU freeing References: <20070509012725.GZ11115@waste.org> <20070508.185141.85412154.davem@davemloft.net> <46412BB5.1060605@yahoo.com.au> <20070509174238.b4152887.akpm@linux-foundation.org> <46426EA1.4030408@yahoo.com.au> <20070510022707.GO11115@waste.org> In-Reply-To: <20070510022707.GO11115@waste.org> Content-Type: multipart/mixed; boundary="------------040502000505000809040805" Sender: owner-linux-mm@kvack.org Return-Path: To: Matt Mackall , Andrew Morton Cc: Linux Memory Management List-ID: This is a multi-part message in MIME format. --------------040502000505000809040805 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Matt Mackall wrote: > Looks good to me, but haven't had time to actually test it. > > Acked-by: Matt Mackall Updated to current, added a comment, and test booted it again. Works OK. -- SUSE Labs, Novell Inc. --------------040502000505000809040805 Content-Type: text/plain; name="slob-add-rcu.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="slob-add-rcu.patch" The SLOB allocator should implement SLAB_DESTROY_BY_RCU correctly, because even on UP, RCU freeing semantics are not equivalent to simply freeing immediately. This also allows SLOB to be used on SMP. Signed-off-by: Nick Piggin Acked-by: Matt Mackall Index: linux-2.6/init/Kconfig =================================================================== --- linux-2.6.orig/init/Kconfig 2007-05-10 14:17:38.000000000 +1000 +++ linux-2.6/init/Kconfig 2007-05-10 14:18:11.000000000 +1000 @@ -519,7 +519,8 @@ slab allocator. config SLUB - depends on EXPERIMENTAL && !ARCH_USES_SLAB_PAGE_STRUCT +# depends on EXPERIMENTAL && !ARCH_USES_SLAB_PAGE_STRUCT + depends on EXPERIMENTAL bool "SLUB (Unqueued Allocator)" help SLUB is a slab allocator that minimizes cache line usage @@ -529,15 +530,11 @@ way and has enhanced diagnostics. config SLOB -# -# SLOB cannot support SMP because SLAB_DESTROY_BY_RCU does not work -# properly. -# - depends on EMBEDDED && !SMP && !SPARSEMEM + depends on EMBEDDED && !SPARSEMEM bool "SLOB (Simple Allocator)" help SLOB replaces the SLAB allocator with a drastically simpler - allocator. SLOB is more space efficient that SLAB but does not + allocator. SLOB is more space efficient than SLAB but does not scale well (single lock for all operations) and is more susceptible to fragmentation. SLOB it is a great choice to reduce memory usage and code size for embedded systems. Index: linux-2.6/mm/slob.c =================================================================== --- linux-2.6.orig/mm/slob.c 2007-05-10 14:17:38.000000000 +1000 +++ linux-2.6/mm/slob.c 2007-05-10 14:59:35.000000000 +1000 @@ -35,6 +35,7 @@ #include #include #include +#include struct slob_block { int units; @@ -53,6 +54,16 @@ }; typedef struct bigblock bigblock_t; +/* + * struct slob_rcu is inserted at the tail of allocated slob blocks, which + * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free + * the block using call_rcu. + */ +struct slob_rcu { + struct rcu_head head; + int size; +}; + static slob_t arena = { .next = &arena, .units = 1 }; static slob_t *slobfree = &arena; static bigblock_t *bigblocks; @@ -266,6 +277,7 @@ struct kmem_cache { unsigned int size, align; + unsigned long flags; const char *name; void (*ctor)(void *, struct kmem_cache *, unsigned long); void (*dtor)(void *, struct kmem_cache *, unsigned long); @@ -283,6 +295,12 @@ if (c) { c->name = name; c->size = size; + if (flags & SLAB_DESTROY_BY_RCU) { + BUG_ON(c->dtor); + /* leave room for rcu footer at the end of object */ + c->size += sizeof(struct slob_rcu); + } + c->flags = flags; c->ctor = ctor; c->dtor = dtor; /* ignore alignment unless it's forced */ @@ -328,15 +346,35 @@ } EXPORT_SYMBOL(kmem_cache_zalloc); -void kmem_cache_free(struct kmem_cache *c, void *b) +static void __kmem_cache_free(void *b, int size) { - if (c->dtor) - c->dtor(b, c, 0); - - if (c->size < PAGE_SIZE) - slob_free(b, c->size); + if (size < PAGE_SIZE) + slob_free(b, size); else - free_pages((unsigned long)b, get_order(c->size)); + free_pages((unsigned long)b, get_order(size)); +} + +static void kmem_rcu_free(struct rcu_head *head) +{ + struct slob_rcu *slob_rcu = (struct slob_rcu *)head; + void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu)); + + __kmem_cache_free(b, slob_rcu->size); +} + +void kmem_cache_free(struct kmem_cache *c, void *b) +{ + if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) { + struct slob_rcu *slob_rcu; + slob_rcu = b + (c->size - sizeof(struct slob_rcu)); + INIT_RCU_HEAD(&slob_rcu->head); + slob_rcu->size = c->size; + call_rcu(&slob_rcu->head, kmem_rcu_free); + } else { + if (c->dtor) + c->dtor(b, c, 0); + __kmem_cache_free(b, c->size); + } } EXPORT_SYMBOL(kmem_cache_free); --------------040502000505000809040805-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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