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From: Lai Jiangshan on 9 Jun 2010 22:30
Hi, Izik

Could you give some comments about this patch.
Thanks,

Lai

Lai Jiangshan wrote:
> Use compile-allocated memory instead of dynamic allocated
> memory for mm_slots_hash.
>
> Use hash_ptr() instead divisions for bucket calculation.
>
> Signed-off-by: Lai Jiangshan <laijs(a)cn.fujitsu.com>
> ---
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 8cdfc2a..81b379e 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -33,6 +33,7 @@
> #include <linux/mmu_notifier.h>
> #include <linux/swap.h>
> #include <linux/ksm.h>
> +#include <linux/hash.h>
>
> #include <asm/tlbflush.h>
> #include "internal.h"
> @@ -153,8 +154,9 @@ struct rmap_item {
> static struct rb_root root_stable_tree = RB_ROOT;
> static struct rb_root root_unstable_tree = RB_ROOT;
>
> -#define MM_SLOTS_HASH_HEADS 1024
> -static struct hlist_head *mm_slots_hash;
> +#define MM_SLOTS_HASH_SHIFT 10
> +#define MM_SLOTS_HASH_HEADS (1 << MM_SLOTS_HASH_SHIFT)
> +static struct hlist_head mm_slots_hash[MM_SLOTS_HASH_HEADS];
>
> static struct mm_slot ksm_mm_head = {
> .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list),
> @@ -269,28 +271,13 @@ static inline void free_mm_slot(struct mm_slot *mm_slot)
> kmem_cache_free(mm_slot_cache, mm_slot);
> }
>
> -static int __init mm_slots_hash_init(void)
> -{
> - mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
> - GFP_KERNEL);
> - if (!mm_slots_hash)
> - return -ENOMEM;
> - return 0;
> -}
> -
> -static void __init mm_slots_hash_free(void)
> -{
> - kfree(mm_slots_hash);
> -}
> -
> static struct mm_slot *get_mm_slot(struct mm_struct *mm)
> {
> struct mm_slot *mm_slot;
> struct hlist_head *bucket;
> struct hlist_node *node;
>
> - bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
> - % MM_SLOTS_HASH_HEADS];
> + bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)];
> hlist_for_each_entry(mm_slot, node, bucket, link) {
> if (mm == mm_slot->mm)
> return mm_slot;
> @@ -303,8 +290,7 @@ static void insert_to_mm_slots_hash(struct mm_struct *mm,
> {
> struct hlist_head *bucket;
>
> - bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
> - % MM_SLOTS_HASH_HEADS];
> + bucket = &mm_slots_hash[hash_ptr(mm, MM_SLOTS_HASH_SHIFT)];
> mm_slot->mm = mm;
> hlist_add_head(&mm_slot->link, bucket);
> }
> @@ -1943,15 +1929,11 @@ static int __init ksm_init(void)
> if (err)
> goto out;
>
> - err = mm_slots_hash_init();
> - if (err)
> - goto out_free1;
> -
> ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd");
> if (IS_ERR(ksm_thread)) {
> printk(KERN_ERR "ksm: creating kthread failed\n");
> err = PTR_ERR(ksm_thread);
> - goto out_free2;
> + goto out_free;
> }
>
> #ifdef CONFIG_SYSFS
> @@ -1959,7 +1941,7 @@ static int __init ksm_init(void)
> if (err) {
> printk(KERN_ERR "ksm: register sysfs failed\n");
> kthread_stop(ksm_thread);
> - goto out_free2;
> + goto out_free;
> }
> #else
> ksm_run = KSM_RUN_MERGE; /* no way for user to start it */
> @@ -1975,9 +1957,7 @@ static int __init ksm_init(void)
> #endif
> return 0;
>
> -out_free2:
> - mm_slots_hash_free();
> -out_free1:
> +out_free:
> ksm_slab_free();
> out:
> return err;
>
> --
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>
>

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From: Andrea Arcangeli on 10 Jun 2010 18:10
Hi Lai,

On Thu, Jun 10, 2010 at 10:23:58AM +0800, Lai Jiangshan wrote:
> Hi, Izik
>
> Could you give some comments about this patch.

I just talked with Izik and he agrees with patch! ;)

Thanks,
Andrea
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From: Avi Kivity on 11 Jun 2010 01:10
On 06/11/2010 01:03 AM, Andrea Arcangeli wrote:
> Hi Lai,
>
> On Thu, Jun 10, 2010 at 10:23:58AM +0800, Lai Jiangshan wrote:
>
>> Hi, Izik
>>
>> Could you give some comments about this patch.
>>
> I just talked with Izik and he agrees with patch! ;)
>
>

Note, to get the patch merged your best bet is to copy linux-mm and
Andrew Morton.

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I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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