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fix SLOB on x64

PATCH In review Ingo Molnar 3 participants 5 messages Dec 11, 2005 Memory management

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Ingo Molnar

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#0 lore raw

PATCH 1/1 fix SLOB on x64

this patch fixes 32-bitness bugs in mm/slob.c. Successfully booted x64 with SLOB enabled. (i have switched the PREEMPT_RT feature to use the SLOB allocator exclusively, so it must work on all platforms)

Signed-off-by Ingo Molnar <[email protected]>
mm/slob.c +3 -3
Index: linux/mm/slob.c
===================================================================
@@ -198,7 +198,7 @@ void kfree(const void *block)
 	if (!block)
 		return;
 
-	if (!((unsigned int)block & (PAGE_SIZE-1))) {
+	if (!((unsigned long)block & (PAGE_SIZE-1))) {
 		/* might be on the big block list */
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {

@@ -227,7 +227,7 @@ unsigned int ksize(const void *block)
 	if (!block)
 		return 0;
 
-	if (!((unsigned int)block & (PAGE_SIZE-1))) {
+	if (!((unsigned long)block & (PAGE_SIZE-1))) {
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; bb = bb->next)
 			if (bb->pages == block) {

@@ -326,7 +326,7 @@ void kmem_cache_init(void)
 	void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
 
 	if (p)
-		free_page((unsigned int)p);
+		free_page((unsigned long)p);
 
 	mod_timer(&slob_timer, jiffies + HZ);
 }
#1 lore raw
Quoted 3 lines · Ingo Molnar

this patch fixes 32-bitness bugs in mm/slob.c. Successfully booted x64 with SLOB enabled. (i have switched the PREEMPT_RT feature to use the SLOB allocator exclusively, so it must work on all platforms)

Its a good idea to get this working everywhere. Why have you switched to use SLOB exclusively?

Thanks
Ed Tomlinson

author
#2 lore raw
Quoted 7 lines · Ed Tomlinson
Quoted 3 lines · Ingo Molnar

this patch fixes 32-bitness bugs in mm/slob.c. Successfully booted x64 with SLOB enabled. (i have switched the PREEMPT_RT feature to use the SLOB allocator exclusively, so it must work on all platforms)

Its a good idea to get this working everywhere. Why have you switched to use SLOB exclusively?

because the SLAB hacks were getting ugly, and i gave up on it during the 2.6.15-rc5 merge. (The SLAB code has lots of irqs-off / per-cpu and non-preempt assumptions integrated, which were a pain to sort out.)

We'll eventually do a cleaner conversion of SLAB to PREEMPT_RT, but for now the SLOB is turned on exclusively if PREEMPT_RT. (in other preemption modes it's optionally selectable if EMBEDDED is enabled)

Ingo

Acked-by on v1 1/1
#3 lore raw
In reply to Ingo Molnar
Quoted 4 lines · Ingo Molnar

this patch fixes 32-bitness bugs in mm/slob.c. Successfully booted x64 with SLOB enabled. (i have switched the PREEMPT_RT feature to use the SLOB allocator exclusively, so it must work on all platforms)

The patch looks fine, but what's this about using SLOB exclusively? Fragmentation performance of SLOB is miserable on anything like a modern desktop, I think SLOB only makes sense for small machines. The locking also suggests dual core at most.

Anyway,

Quoted 1 line
Signed-off-by Ingo Molnar <[email protected]>
Acked-by Matt Mackall <[email protected]>
Quoted 32 lines

Index: linux/mm/slob.c
===================================================================

mm/slob.c +3 -3
@@ -198,7 +198,7 @@ void kfree(const void *block)
 	if (!block)
 		return;
 
-	if (!((unsigned int)block & (PAGE_SIZE-1))) {
+	if (!((unsigned long)block & (PAGE_SIZE-1))) {
 		/* might be on the big block list */
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {

@@ -227,7 +227,7 @@ unsigned int ksize(const void *block)
 	if (!block)
 		return 0;
 
-	if (!((unsigned int)block & (PAGE_SIZE-1))) {
+	if (!((unsigned long)block & (PAGE_SIZE-1))) {
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; bb = bb->next)
 			if (bb->pages == block) {

@@ -326,7 +326,7 @@ void kmem_cache_init(void)
 	void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
 
 	if (p)
-		free_page((unsigned int)p);
+		free_page((unsigned long)p);
 
 	mod_timer(&slob_timer, jiffies + HZ);
 }
Signature · 1 line
Mathematics is the supreme nostalgia of our time.
author
#4 lore raw
Quoted 10 lines · Matt Mackall
Quoted 4 lines · Ingo Molnar

this patch fixes 32-bitness bugs in mm/slob.c. Successfully booted x64 with SLOB enabled. (i have switched the PREEMPT_RT feature to use the SLOB allocator exclusively, so it must work on all platforms)

The patch looks fine, but what's this about using SLOB exclusively? Fragmentation performance of SLOB is miserable on anything like a modern desktop, I think SLOB only makes sense for small machines. The locking also suggests dual core at most.

well, this is only an -rt artifact: the SLOB needs zero modifications to work on PREEMPT_RT, while SLAB needed a risky 66K monster patch. Until someone simplifies the SLAB conversion to PREEMPT_RT, i'll use the SLOB.

i havent noticed any significant slowdown due to the SLOB. In any case, we'll give it some workout which should further speed up its upstream integration - it's looking good so far.

Ingo