Re: [patch] SLQB slab allocator (try 2)

["Zhang, Yanmin" <yanmin_zhang@linux.intel.com>]

On Tue, 2009-02-17 at 12:05 -0500, Christoph Lameter wrote:
> Well yes you missed two locations (kmalloc_caches array has to be
> redimensioned) and I also was writing the same patch...
> 
> Here is mine:
> 
> Subject: SLUB: Do not pass 8k objects through to the page allocator
> 
> Increase the maximum object size in SLUB so that 8k objects are not
> passed through to the page allocator anymore. The network stack uses 8k
> objects for performance critical operations.
Kernel 2.6.29-rc2 panic with the patch.

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8028fae3>] kmem_cache_alloc+0x43/0x97
PGD 0 
Oops: 0000 [#1] SMP 
last sysfs file: 
CPU 0 
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.29-rc2slubstat8k #1
RIP: 0010:[<ffffffff8028fae3>]  [<ffffffff8028fae3>] kmem_cache_alloc+0x43/0x97
RSP: 0018:ffff88022f865e20  EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 000000000000063f RDI: ffffffff808096c7
RBP: 00000000000000d0 R08: 0000000000000004 R09: 000000000012e941
R10: 0000000000000002 R11: 0000000000000020 R12: ffffffff80991c48
R13: ffffffff809a9b43 R14: ffffffff809f8000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffffffff80a13080(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 0000000000201000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process swapper (pid: 1, threadinfo ffff88022f864000, task ffff88022f868000)
Stack:
 ffffffff809f43e0 0000000000000020 ffffffff809aa469 0000000000000086
 ffffffff809f8000 ffffffff809a9b43 ffffffff80aaae80 ffffffff809f43e0
 0000000000000020 ffffffff809aa469 0000000000000000 ffffffff809d86a0
Call Trace:
 [<ffffffff809aa469>] ? populate_rootfs+0x0/0xdf
 [<ffffffff809a9b43>] ? unpack_to_rootfs+0x59/0x97f
 [<ffffffff809aa469>] ? populate_rootfs+0x0/0xdf
 [<ffffffff809aa481>] ? populate_rootfs+0x18/0xdf
 [<ffffffff80209051>] ? _stext+0x51/0x120
 [<ffffffff802d69b2>] ? create_proc_entry+0x73/0x8a
 [<ffffffff802619c0>] ? register_irq_proc+0x92/0xaa
 [<ffffffff809a4896>] ? kernel_init+0x12e/0x188
 [<ffffffff8020ce3a>] ? child_rip+0xa/0x20
 [<ffffffff809a4768>] ? kernel_init+0x0/0x188
 [<ffffffff8020ce30>] ? child_rip+0x0/0x20
Code: be 3f 06 00 00 48 c7 c7 c7 96 80 80 e8 b8 e2 f9 ff e8 c5 c2 45 00 9c 5b fa 65 8b 04 25 24 00 00 00 48 98 49 8b 94 c4 e8  
RIP  [<ffffffff8028fae3>] kmem_cache_alloc+0x43/0x97
 RSP <ffff88022f865e20>
CR2: 0000000000000000
---[ end trace a7919e7f17c0a725 ]---
swapper used greatest stack depth: 5376 bytes left
Kernel panic - not syncing: Attempted to kill init!

> 
> Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
> 
> Index: linux-2.6/include/linux/slub_def.h
> ===================================================================
> --- linux-2.6.orig/include/linux/slub_def.h	2009-02-17 10:45:51.000000000 -0600
> +++ linux-2.6/include/linux/slub_def.h	2009-02-17 11:06:53.000000000 -0600
> @@ -121,10 +121,21 @@
>  #define KMALLOC_SHIFT_LOW ilog2(KMALLOC_MIN_SIZE)
> 
>  /*
> + * Maximum kmalloc object size handled by SLUB. Larger object allocations
> + * are passed through to the page allocator. The page allocator "fastpath"
> + * is relatively slow so we need this value sufficiently high so that
> + * performance critical objects are allocated through the SLUB fastpath.
> + *
> + * This should be dropped to PAGE_SIZE / 2 once the page allocator
> + * "fastpath" becomes competitive with the slab allocator fastpaths.
> + */
> +#define SLUB_MAX_SIZE (2 * PAGE_SIZE)
> +
> +/*
>   * We keep the general caches in an array of slab caches that are used for
>   * 2^x bytes of allocations.
>   */
> -extern struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1];
> +extern struct kmem_cache kmalloc_caches[PAGE_SHIFT + 2];
> 
>  /*
>   * Sorry that the following has to be that ugly but some versions of GCC
> @@ -212,7 +223,7 @@
>  static __always_inline void *kmalloc(size_t size, gfp_t flags)
>  {
>  	if (__builtin_constant_p(size)) {
> -		if (size > PAGE_SIZE)
> +		if (size > SLUB_MAX_SIZE)
>  			return kmalloc_large(size, flags);
> 
>  		if (!(flags & SLUB_DMA)) {
> @@ -234,7 +245,7 @@
>  static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
>  {
>  	if (__builtin_constant_p(size) &&
> -		size <= PAGE_SIZE && !(flags & SLUB_DMA)) {
> +		size <= SLUB_MAX_SIZE && !(flags & SLUB_DMA)) {
>  			struct kmem_cache *s = kmalloc_slab(size);
> 
>  		if (!s)
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2009-02-17 10:49:47.000000000 -0600
> +++ linux-2.6/mm/slub.c	2009-02-17 10:58:14.000000000 -0600
> @@ -2475,7 +2475,7 @@
>   *		Kmalloc subsystem
>   *******************************************************************/
> 
> -struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1] __cacheline_aligned;
> +struct kmem_cache kmalloc_caches[PAGE_SHIFT + 2] __cacheline_aligned;
>  EXPORT_SYMBOL(kmalloc_caches);
> 
>  static int __init setup_slub_min_order(char *str)
> @@ -2658,7 +2658,7 @@
>  {
>  	struct kmem_cache *s;
> 
> -	if (unlikely(size > PAGE_SIZE))
> +	if (unlikely(size > SLUB_MAX_SIZE))
>  		return kmalloc_large(size, flags);
> 
>  	s = get_slab(size, flags);
> @@ -2686,7 +2686,7 @@
>  {
>  	struct kmem_cache *s;
> 
> -	if (unlikely(size > PAGE_SIZE))
> +	if (unlikely(size > SLUB_MAX_SIZE))
>  		return kmalloc_large_node(size, flags, node);
> 
>  	s = get_slab(size, flags);
> @@ -3223,7 +3223,7 @@
>  {
>  	struct kmem_cache *s;
> 
> -	if (unlikely(size > PAGE_SIZE))
> +	if (unlikely(size > SLUB_MAX_SIZE))
>  		return kmalloc_large(size, gfpflags);
> 
>  	s = get_slab(size, gfpflags);
> @@ -3239,7 +3239,7 @@
>  {
>  	struct kmem_cache *s;
> 
> -	if (unlikely(size > PAGE_SIZE))
> +	if (unlikely(size > SLUB_MAX_SIZE))
>  		return kmalloc_large_node(size, gfpflags, node);
> 
>  	s = get_slab(size, gfpflags);