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Message-Id: <1234943296.24030.2.camel@penberg-laptop>
Date: Wed, 18 Feb 2009 09:48:16 +0200
From: Pekka Enberg <penberg@...helsinki.fi>
To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc: Christoph Lameter <cl@...ux-foundation.org>,
Mel Gorman <mel@....ul.ie>,
Nick Piggin <nickpiggin@...oo.com.au>,
Nick Piggin <npiggin@...e.de>,
Linux Memory Management List <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Lin Ming <ming.m.lin@...el.com>
Subject: Re: [patch] SLQB slab allocator (try 2)
Hi Yanmin,
On Wed, 2009-02-18 at 09:05 +0800, Zhang, Yanmin wrote:
> 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!
Aah, we need to fix up some more PAGE_SHIFTs in the code.
Pekka
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 2f5c16b..e217a7a 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -121,10 +121,23 @@ struct kmem_cache {
#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)
+
+#define SLUB_PAGE_SHIFT (PAGE_SHIFT + 2)
+
+/*
* 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[SLUB_PAGE_SHIFT];
/*
* Sorry that the following has to be that ugly but some versions of GCC
@@ -212,7 +225,7 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
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 +247,7 @@ void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
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)
diff --git a/mm/slub.c b/mm/slub.c
index 0280eee..43a0c53 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2475,7 +2475,7 @@ EXPORT_SYMBOL(kmem_cache_destroy);
* Kmalloc subsystem
*******************************************************************/
-struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1] __cacheline_aligned;
+struct kmem_cache kmalloc_caches[SLUB_PAGE_SHIFT] __cacheline_aligned;
EXPORT_SYMBOL(kmalloc_caches);
static int __init setup_slub_min_order(char *str)
@@ -2537,7 +2537,7 @@ panic:
}
#ifdef CONFIG_ZONE_DMA
-static struct kmem_cache *kmalloc_caches_dma[PAGE_SHIFT + 1];
+static struct kmem_cache *kmalloc_caches_dma[SLUB_PAGE_SHIFT];
static void sysfs_add_func(struct work_struct *w)
{
@@ -2658,7 +2658,7 @@ void *__kmalloc(size_t size, gfp_t flags)
{
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 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
{
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);
@@ -2986,7 +2986,7 @@ void __init kmem_cache_init(void)
caches++;
}
- for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++) {
+ for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
create_kmalloc_cache(&kmalloc_caches[i],
"kmalloc", 1 << i, GFP_KERNEL);
caches++;
@@ -3023,7 +3023,7 @@ void __init kmem_cache_init(void)
slab_state = UP;
/* Provide the correct kmalloc names now that the caches are up */
- for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++)
+ for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++)
kmalloc_caches[i]. name =
kasprintf(GFP_KERNEL, "kmalloc-%d", 1 << i);
@@ -3223,7 +3223,7 @@ void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
{
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 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
{
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);
--
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