Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
William Lee Irwin III a ?crit : >> The proper way to do this is to convert the large system hashtable >> users to use some data structure / algorithm other than hashing by >> separate chaining. On Sat, May 19, 2007 at 08:41:01PM +0200, Eric Dumazet wrote: > No thanks. This was already discussed to death on netdev. To date, hash > tables are a good compromise. > I dont mind losing part of memory, I prefer to keep good performance when > handling 1.000.000 or more tcp sessions. The data structures perform well enough, but I suppose it's not worth pushing the issue this way. -- wli - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
William Lee Irwin III a ?crit : The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. On Sat, May 19, 2007 at 08:41:01PM +0200, Eric Dumazet wrote: No thanks. This was already discussed to death on netdev. To date, hash tables are a good compromise. I dont mind losing part of memory, I prefer to keep good performance when handling 1.000.000 or more tcp sessions. The data structures perform well enough, but I suppose it's not worth pushing the issue this way. -- wli - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
David Miller a écrit :
From: Eric Dumazet <[EMAIL PROTECTED]>
Date: Sat, 19 May 2007 20:07:11 +0200
Maybe David has an idea how this can be done properly ?
ref : http://marc.info/?l=linux-netdev=117706074825048=2
You need to use __GFP_COMP or similar to make this splitting+freeing
thing work.
Otherwise the individual pages don't have page references, only
the head page of the high-order page will.
Oh thanks David for the hint.
I added a split_page() call and it seems to work now.
[PATCH] MM : alloc_large_system_hash() can free some memory for non
power-of-two bucketsize
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order > 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..7c219eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,21 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL << order) << PAGE_SHIFT) < size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE << order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ split_page(virt_to_page(table), order);
+ while (used < alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table && size > PAGE_SIZE && --log2qty);
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
From: Eric Dumazet <[EMAIL PROTECTED]> Date: Sat, 19 May 2007 20:07:11 +0200 > Maybe David has an idea how this can be done properly ? > > ref : http://marc.info/?l=linux-netdev=117706074825048=2 You need to use __GFP_COMP or similar to make this splitting+freeing thing work. Otherwise the individual pages don't have page references, only the head page of the high-order page will. - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
William Lee Irwin III a écrit : On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote: alloc_large_system_hash() is called at boot time to allocate space for several large hash tables. Lately, TCP hash table was changed and its bucketsize is not a power-of-two anymore. On most setups, alloc_large_system_hash() allocates one big page (order > 0) with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a power-of-two size, bigger than the needed size. We can free all pages that wont be used by the hash table. On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory. TCP established hash table entries: 32768 (order: 6, 393216 bytes) The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. No thanks. This was already discussed to death on netdev. To date, hash tables are a good compromise. I dont mind losing part of memory, I prefer to keep good performance when handling 1.000.000 or more tcp sessions. - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote: > alloc_large_system_hash() is called at boot time to allocate space > for several large hash tables. > Lately, TCP hash table was changed and its bucketsize is not a > power-of-two anymore. > On most setups, alloc_large_system_hash() allocates one big page > (order > 0) with __get_free_pages(GFP_ATOMIC, order). This single > high_order page has a power-of-two size, bigger than the needed size. > We can free all pages that wont be used by the hash table. > On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory. > TCP established hash table entries: 32768 (order: 6, 393216 bytes) The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. -- wli - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
Andrew Morton a écrit :
On Fri, 18 May 2007 11:54:54 +0200 Eric Dumazet <[EMAIL PROTECTED]> wrote:
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order > 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
Watch the 200-column text, please.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..2e0ba08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL << order) << PAGE_SHIFT) < size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE << order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used < alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table && size > PAGE_SIZE && --log2qty);
It went BUG.
static inline int put_page_testzero(struct page *page)
{
VM_BUG_ON(atomic_read(>_count) == 0);
return atomic_dec_and_test(>_count);
}
http://userweb.kernel.org/~akpm/s5000523.jpg
http://userweb.kernel.org/~akpm/config-vmm.txt
I see :(
Maybe David has an idea how this can be done properly ?
ref : http://marc.info/?l=linux-netdev=117706074825048=2
-
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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, 18 May 2007 11:54:54 +0200 Eric Dumazet <[EMAIL PROTECTED]> wrote:
> alloc_large_system_hash() is called at boot time to allocate space for
> several large hash tables.
>
> Lately, TCP hash table was changed and its bucketsize is not a power-of-two
> anymore.
>
> On most setups, alloc_large_system_hash() allocates one big page (order > 0)
> with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
> power-of-two size, bigger than the needed size.
Watch the 200-column text, please.
> We can free all pages that wont be used by the hash table.
>
> On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
>
> TCP established hash table entries: 32768 (order: 6, 393216 bytes)
>
> Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
> ---
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ae96dd8..2e0ba08 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
> *tablename,
> for (order = 0; ((1UL << order) << PAGE_SHIFT) < size;
> order++)
> ;
> table = (void*) __get_free_pages(GFP_ATOMIC, order);
> + /*
> + * If bucketsize is not a power-of-two, we may free
> + * some pages at the end of hash table.
> + */
> + if (table) {
> + unsigned long alloc_end = (unsigned long)table +
> + (PAGE_SIZE << order);
> + unsigned long used = (unsigned long)table +
> + PAGE_ALIGN(size);
> + while (used < alloc_end) {
> + free_page(used);
> + used += PAGE_SIZE;
> + }
> + }
> }
> } while (!table && size > PAGE_SIZE && --log2qty);
>
It went BUG.
static inline int put_page_testzero(struct page *page)
{
VM_BUG_ON(atomic_read(>_count) == 0);
return atomic_dec_and_test(>_count);
}
http://userweb.kernel.org/~akpm/s5000523.jpg
http://userweb.kernel.org/~akpm/config-vmm.txt
-
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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, 18 May 2007 11:54:54 +0200 Eric Dumazet [EMAIL PROTECTED] wrote:
alloc_large_system_hash() is called at boot time to allocate space for
several large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
Watch the 200-column text, please.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet [EMAIL PROTECTED]
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..2e0ba08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL order) PAGE_SHIFT) size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+ * If bucketsize is not a power-of-two, we may free
+ * some pages at the end of hash table.
+ */
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table size PAGE_SIZE --log2qty);
It went BUG.
static inline int put_page_testzero(struct page *page)
{
VM_BUG_ON(atomic_read(page-_count) == 0);
return atomic_dec_and_test(page-_count);
}
http://userweb.kernel.org/~akpm/s5000523.jpg
http://userweb.kernel.org/~akpm/config-vmm.txt
-
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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
Andrew Morton a écrit :
On Fri, 18 May 2007 11:54:54 +0200 Eric Dumazet [EMAIL PROTECTED] wrote:
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
Watch the 200-column text, please.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet [EMAIL PROTECTED]
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..2e0ba08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL order) PAGE_SHIFT) size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table size PAGE_SIZE --log2qty);
It went BUG.
static inline int put_page_testzero(struct page *page)
{
VM_BUG_ON(atomic_read(page-_count) == 0);
return atomic_dec_and_test(page-_count);
}
http://userweb.kernel.org/~akpm/s5000523.jpg
http://userweb.kernel.org/~akpm/config-vmm.txt
I see :(
Maybe David has an idea how this can be done properly ?
ref : http://marc.info/?l=linux-netdevm=117706074825048w=2
-
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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote: alloc_large_system_hash() is called at boot time to allocate space for several large hash tables. Lately, TCP hash table was changed and its bucketsize is not a power-of-two anymore. On most setups, alloc_large_system_hash() allocates one big page (order 0) with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a power-of-two size, bigger than the needed size. We can free all pages that wont be used by the hash table. On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory. TCP established hash table entries: 32768 (order: 6, 393216 bytes) The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. -- wli - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
William Lee Irwin III a écrit : On Fri, May 18, 2007 at 11:54:54AM +0200, Eric Dumazet wrote: alloc_large_system_hash() is called at boot time to allocate space for several large hash tables. Lately, TCP hash table was changed and its bucketsize is not a power-of-two anymore. On most setups, alloc_large_system_hash() allocates one big page (order 0) with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a power-of-two size, bigger than the needed size. We can free all pages that wont be used by the hash table. On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory. TCP established hash table entries: 32768 (order: 6, 393216 bytes) The proper way to do this is to convert the large system hashtable users to use some data structure / algorithm other than hashing by separate chaining. No thanks. This was already discussed to death on netdev. To date, hash tables are a good compromise. I dont mind losing part of memory, I prefer to keep good performance when handling 1.000.000 or more tcp sessions. - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
From: Eric Dumazet [EMAIL PROTECTED] Date: Sat, 19 May 2007 20:07:11 +0200 Maybe David has an idea how this can be done properly ? ref : http://marc.info/?l=linux-netdevm=117706074825048w=2 You need to use __GFP_COMP or similar to make this splitting+freeing thing work. Otherwise the individual pages don't have page references, only the head page of the high-order page will. - 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/
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
David Miller a écrit :
From: Eric Dumazet [EMAIL PROTECTED]
Date: Sat, 19 May 2007 20:07:11 +0200
Maybe David has an idea how this can be done properly ?
ref : http://marc.info/?l=linux-netdevm=117706074825048w=2
You need to use __GFP_COMP or similar to make this splitting+freeing
thing work.
Otherwise the individual pages don't have page references, only
the head page of the high-order page will.
Oh thanks David for the hint.
I added a split_page() call and it seems to work now.
[PATCH] MM : alloc_large_system_hash() can free some memory for non
power-of-two bucketsize
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet [EMAIL PROTECTED]
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..7c219eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,21 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL order) PAGE_SHIFT) size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ split_page(virt_to_page(table), order);
+ while (used alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table size PAGE_SIZE --log2qty);
Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, 18 May 2007, Eric Dumazet wrote:
> table = (void*) __get_free_pages(GFP_ATOMIC, order);
ATOMIC? Is there some reason why we need atomic here?
> + /*
> + * If bucketsize is not a power-of-two, we may free
> + * some pages at the end of hash table.
> + */
> + if (table) {
> + unsigned long alloc_end = (unsigned long)table +
> + (PAGE_SIZE << order);
> + unsigned long used = (unsigned long)table +
> + PAGE_ALIGN(size);
> + while (used < alloc_end) {
> + free_page(used);
Isnt this going to interfere with the kernel_map_pages debug stuff?
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order > 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..2e0ba08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL << order) << PAGE_SHIFT) < size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE << order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used < alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table && size > PAGE_SIZE && --log2qty);
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
alloc_large_system_hash() is called at boot time to allocate space for several
large hash tables.
Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.
On most setups, alloc_large_system_hash() allocates one big page (order 0)
with __get_free_pages(GFP_ATOMIC, order). This single high_order page has a
power-of-two size, bigger than the needed size.
We can free all pages that wont be used by the hash table.
On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
TCP established hash table entries: 32768 (order: 6, 393216 bytes)
Signed-off-by: Eric Dumazet [EMAIL PROTECTED]
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ae96dd8..2e0ba08 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3350,6 +3350,20 @@ void *__init alloc_large_system_hash(const char
*tablename,
for (order = 0; ((1UL order) PAGE_SHIFT) size;
order++)
;
table = (void*) __get_free_pages(GFP_ATOMIC, order);
+ /*
+* If bucketsize is not a power-of-two, we may free
+* some pages at the end of hash table.
+*/
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used alloc_end) {
+ free_page(used);
+ used += PAGE_SIZE;
+ }
+ }
}
} while (!table size PAGE_SIZE --log2qty);
-
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Re: [PATCH] MM : alloc_large_system_hash() can free some memory for non power-of-two bucketsize
On Fri, 18 May 2007, Eric Dumazet wrote:
table = (void*) __get_free_pages(GFP_ATOMIC, order);
ATOMIC? Is there some reason why we need atomic here?
+ /*
+ * If bucketsize is not a power-of-two, we may free
+ * some pages at the end of hash table.
+ */
+ if (table) {
+ unsigned long alloc_end = (unsigned long)table +
+ (PAGE_SIZE order);
+ unsigned long used = (unsigned long)table +
+ PAGE_ALIGN(size);
+ while (used alloc_end) {
+ free_page(used);
Isnt this going to interfere with the kernel_map_pages debug stuff?
-
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