Martin Wilck <[email protected]> wrote:
>
> Hello,
>
> I have recently seen massive problems with the bounce buffer allocation
> implementation in 2.6. My system got OOM with an ata_piix controller
> (4GB bounce limit), 2 P4 CPUs and 8GB of RAM with a very simple
> copy-compare test: About 800MB worth of data are copied with cp(1) in 7
> synchronous jobs. Each job does a sync(1) after the copy.
Fair enough.
> ...
>
> The attached quick-and-dirty patch gives you an idea of what I figured
> could be a useful workaround for that problem. It follows 2 main ideas:
>
> 1 When bounce buffer allocations fail, it is wrong to trigger the page
> reclaim mechanism which is likely to genetate even more bounce buffer
> requests. Thus there should be no wakeup_bdflush() call for the
> page_pool.
>
> 2 bounce buffer allocations should not simply use alloc_page() because
> there is no limit for allocations that way. Rather, bounce buffer
> allocations should stop if ZONE_NORMAL is full to a certain degree
> (my patch stops at 51% - chosen arbitrarily).
It might be neater to do this at the mempool level: that way we're adding
general-purpose infrastructure and then just using it, rather than
special-casing the bounce code.
See below a (n untested) patch against the latest devel tree. It won't be
stunningly scalable on big SMP, but the overhead of bouncing will probably
hide that.
> I couldn't get 2.6.12-rc5 to run on my system.
Ow. Could you please investigate further? Any boot messages for us to
see? it's quite possibly some missing config option..
include/linux/mempool.h | 17 +++++++++++++++--
mm/highmem.c | 4 +++-
mm/mempool.c | 17 +++++++++++++----
3 files changed, 31 insertions(+), 7 deletions(-)
diff -puN include/linux/mempool.h~mempool-bounce-buffer-restriction include/linux/mempool.h
--- 25/include/linux/mempool.h~mempool-bounce-buffer-restriction Fri Jun 3 16:01:58 2005
+++ 25-akpm/include/linux/mempool.h Fri Jun 3 16:01:58 2005
@@ -5,6 +5,7 @@
#define _LINUX_MEMPOOL_H
#include <linux/wait.h>
+#include <asm/semaphore.h>
typedef void * (mempool_alloc_t)(unsigned int __nocast gfp_mask, void *pool_data);
typedef void (mempool_free_t)(void *element, void *pool_data);
@@ -14,14 +15,26 @@ typedef struct mempool_s {
int min_nr; /* nr of elements at *elements */
int curr_nr; /* Current nr of elements at *elements */
void **elements;
+ int limit;
void *pool_data;
mempool_alloc_t *alloc;
mempool_free_t *free;
wait_queue_head_t wait;
+ struct semaphore limit_sem;
} mempool_t;
-extern mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
- mempool_free_t *free_fn, void *pool_data);
+
+extern mempool_t *mempool_create_restricted(int min_nr,
+ mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
+ void *pool_data, int limit);
+
+static inline mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
+ mempool_free_t *free_fn, void *pool_data)
+{
+ return mempool_create_restricted(min_nr, alloc_fn, free_fn,
+ pool_data, 0);
+}
+
extern int mempool_resize(mempool_t *pool, int new_min_nr, unsigned int __nocast gfp_mask);
extern void mempool_destroy(mempool_t *pool);
extern void * mempool_alloc(mempool_t *pool, unsigned int __nocast gfp_mask);
diff -puN mm/highmem.c~mempool-bounce-buffer-restriction mm/highmem.c
--- 25/mm/highmem.c~mempool-bounce-buffer-restriction Fri Jun 3 16:01:58 2005
+++ 25-akpm/mm/highmem.c Fri Jun 3 16:01:58 2005
@@ -224,7 +224,9 @@ static __init int init_emergency_pool(vo
if (!i.totalhigh)
return 0;
- page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
+ page_pool = mempool_create_restricted(POOL_SIZE, page_pool_alloc,
+ page_pool_free, NULL,
+ 200 * 1024 * 1024 / PAGE_SIZE);
if (!page_pool)
BUG();
printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
diff -puN mm/mempool.c~mempool-bounce-buffer-restriction mm/mempool.c
--- 25/mm/mempool.c~mempool-bounce-buffer-restriction Fri Jun 3 16:01:58 2005
+++ 25-akpm/mm/mempool.c Fri Jun 3 16:01:58 2005
@@ -38,12 +38,13 @@ static void free_pool(mempool_t *pool)
}
/**
- * mempool_create - create a memory pool
+ * mempool_create_restricted - create a memory pool
* @min_nr: the minimum number of elements guaranteed to be
* allocated for this pool.
* @alloc_fn: user-defined element-allocation function.
* @free_fn: user-defined element-freeing function.
* @pool_data: optional private data available to the user-defined functions.
+ * @limit: maximum number of in-flight objects
*
* this function creates and allocates a guaranteed size, preallocated
* memory pool. The pool can be used from the mempool_alloc and mempool_free
@@ -51,8 +52,8 @@ static void free_pool(mempool_t *pool)
* functions might sleep - as long as the mempool_alloc function is not called
* from IRQ contexts.
*/
-mempool_t * mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
- mempool_free_t *free_fn, void *pool_data)
+mempool_t *mempool_create_restricted(int min_nr, mempool_alloc_t *alloc_fn,
+ mempool_free_t *free_fn, void *pool_data, int limit)
{
mempool_t *pool;
@@ -71,6 +72,8 @@ mempool_t * mempool_create(int min_nr, m
init_waitqueue_head(&pool->wait);
pool->alloc = alloc_fn;
pool->free = free_fn;
+ pool->limit = limit;
+ sema_init(&pool->limit_sem, limit);
/*
* First pre-allocate the guaranteed number of buffers.
@@ -87,7 +90,7 @@ mempool_t * mempool_create(int min_nr, m
}
return pool;
}
-EXPORT_SYMBOL(mempool_create);
+EXPORT_SYMBOL(mempool_create_restricted);
/**
* mempool_resize - resize an existing memory pool
@@ -208,6 +211,9 @@ void * mempool_alloc(mempool_t *pool, un
gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
+ if (unlikely(pool->limit))
+ down(&pool->limit_sem);
+
repeat_alloc:
element = pool->alloc(gfp_temp, pool->pool_data);
@@ -250,6 +256,9 @@ void mempool_free(void *element, mempool
{
unsigned long flags;
+ if (unlikely(pool->limit))
+ up(&pool->limit_sem);
+
smp_mb();
if (pool->curr_nr < pool->min_nr) {
spin_lock_irqsave(&pool->lock, flags);
_
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
