Changelog:
v2 -> v3:
* increment/decrement zcache_[eph|pers]_zpages for zero-filled pages, spotted by Dan
* replace "zero" or "zero page" by "zero_filled_page", spotted by Dan
v1 -> v2:
* avoid changing tmem.[ch] entirely, spotted by Dan.
* don't accumulate [eph|pers]pageframe and [eph|pers]zpages for
zero-filled pages, spotted by Dan
* cleanup TODO list
* add Dan Acked-by.
Motivation:
- Seth Jennings points out compress zero-filled pages with LZO(a lossless
data compression algorithm) will waste memory and result in fragmentation.
https://lkml.org/lkml/2012/8/14/347
- Dan Magenheimer add "Support zero-filled pages more efficiently" feature
in zcache TODO list https://lkml.org/lkml/2013/2/13/503
Design:
- For store page, capture zero-filled pages(evicted clean page cache pages and
swap pages), but don't compress them, set pampd which store zpage address to
0x2(since 0x0 and 0x1 has already been ocuppied) to mark special zero-filled
case and take advantage of tmem infrastructure to transform handle-tuple(pool
id, object id, and an index) to a pampd. Twice compress zero-filled pages will
contribute to one zcache_[eph|pers]_pageframes count accumulated.
- For load page, traverse tmem hierachical to transform handle-tuple to pampd
and identify zero-filled case by pampd equal to 0x2 when filesystem reads
file pages or a page needs to be swapped in, then refill the page to zero
and return.
Test:
dd if=/dev/zero of=zerofile bs=1MB count=500
vmtouch -t zerofile
vmtouch -e zerofile
formula:
- fragmentation level = (zcache_[eph|pers]_pageframes * PAGE_SIZE - zcache_[eph|pers]_zbytes)
* 100 / (zcache_[eph|pers]_pageframes * PAGE_SIZE)
- memory zcache occupy = zcache_[eph|pers]_zbytes
Result:
without zero-filled awareness:
- fragmentation level: 98%
- memory zcache occupy: 238MB
with zero-filled awareness:
- fragmentation level: 0%
- memory zcache occupy: 0MB
Wanpeng Li (5):
introduce zero-filled pages handler
zero-filled pages awareness
handle zcache_[eph|pers]_zpages for zero-filled page
introduce zero-filled page stat count
clean TODO list
drivers/staging/zcache/TODO | 3 +-
drivers/staging/zcache/zcache-main.c | 119 ++++++++++++++++++++++++++++++++--
2 files changed, 114 insertions(+), 8 deletions(-)
--
1.7.7.6
Introduce zero-filled pages handler to capture and handle zero pages.
Acked-by: Dan Magenheimer <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
drivers/staging/zcache/zcache-main.c | 26 ++++++++++++++++++++++++++
1 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 328898e..d73dd4b 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -460,6 +460,32 @@ static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
kmem_cache_free(zcache_obj_cache, obj);
}
+static bool page_is_zero_filled(void *ptr)
+{
+ unsigned int pos;
+ unsigned long *page;
+
+ page = (unsigned long *)ptr;
+
+ for (pos = 0; pos < PAGE_SIZE / sizeof(*page); pos++) {
+ if (page[pos])
+ return false;
+ }
+
+ return true;
+}
+
+static void handle_zero_filled_page(void *page)
+{
+ void *user_mem;
+
+ user_mem = kmap_atomic(page);
+ memset(user_mem, 0, PAGE_SIZE);
+ kunmap_atomic(user_mem);
+
+ flush_dcache_page(page);
+}
+
static struct tmem_hostops zcache_hostops = {
.obj_alloc = zcache_obj_alloc,
.obj_free = zcache_obj_free,
--
1.7.7.6
Cleanup TODO list since support zero-filled pages more efficiently has
already done by this patchset.
Acked-by: Dan Magenheimer <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
drivers/staging/zcache/TODO | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/zcache/TODO b/drivers/staging/zcache/TODO
index c1e26d4..9e755d3 100644
--- a/drivers/staging/zcache/TODO
+++ b/drivers/staging/zcache/TODO
@@ -65,5 +65,4 @@ ZCACHE FUTURE NEW FUNCTIONALITY
A. Support zsmalloc as an alternative high-density allocator
(See https://lkml.org/lkml/2013/1/23/511)
-B. Support zero-filled pages more efficiently
-C. Possibly support three zbuds per pageframe when space allows
+B. Possibly support three zbuds per pageframe when space allows
--
1.7.7.6
Increment/decrement zcache_[eph|pers]_zpages for zero-filled pages,
the main point of the counters for zpages and pageframes is to be
able to calculate density == zpages/pageframes. A zero-filled page
becomes a zpage that "compresses" to zero bytes and, as a result,
requires zero pageframes for storage. So the zpages counter should
be increased but the pageframes counter should not.
[Dan Magenheimer <[email protected]>: patch description]
Acked-by: Dan Magenheimer <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
drivers/staging/zcache/zcache-main.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 6c35c7d..ef8c960 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -863,6 +863,8 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
if (pampd == (void *)ZERO_FILLED) {
handle_zero_filled_page(data);
zero_filled = true;
+ zsize = 0;
+ zpages = 1;
if (!raw)
*sizep = PAGE_SIZE;
goto zero_fill;
@@ -917,8 +919,11 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
BUG_ON(preemptible());
- if (pampd == (void *)ZERO_FILLED)
+ if (pampd == (void *)ZERO_FILLED) {
zero_filled = true;
+ zsize = 0;
+ zpages = 1;
+ }
if (pampd_is_remote(pampd) && !zero_filled) {
--
1.7.7.6
Introduce zero-filled page statistics to monitor the number of
zero-filled pages.
Acked-by: Dan Magenheimer <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
drivers/staging/zcache/zcache-main.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index ef8c960..bc7ccbb 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -197,6 +197,7 @@ static ssize_t zcache_eph_nonactive_puts_ignored;
static ssize_t zcache_pers_nonactive_puts_ignored;
static ssize_t zcache_writtenback_pages;
static ssize_t zcache_outstanding_writeback_pages;
+static ssize_t zcache_zero_filled_pages;
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
@@ -258,6 +259,7 @@ static int zcache_debugfs_init(void)
zdfs("outstanding_writeback_pages", S_IRUGO, root,
&zcache_outstanding_writeback_pages);
zdfs("writtenback_pages", S_IRUGO, root, &zcache_writtenback_pages);
+ zdfs("zero_filled_pages", S_IRUGO, root, &zcache_zero_filled_pages);
return 0;
}
#undef zdebugfs
@@ -327,6 +329,7 @@ void zcache_dump(void)
pr_info("zcache: outstanding_writeback_pages=%zd\n",
zcache_outstanding_writeback_pages);
pr_info("zcache: writtenback_pages=%zd\n", zcache_writtenback_pages);
+ pr_info("zcache: zero_filled_pages=%zd\n", zcache_zero_filled_pages);
}
#endif
@@ -563,6 +566,7 @@ static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
kunmap_atomic(user_mem);
clen = 0;
zero_filled = true;
+ zcache_zero_filled_pages++;
goto got_pampd;
}
kunmap_atomic(user_mem);
@@ -646,6 +650,7 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
kunmap_atomic(user_mem);
clen = 0;
zero_filled = true;
+ zcache_zero_filled_pages++;
goto got_pampd;
}
kunmap_atomic(user_mem);
@@ -867,6 +872,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
zpages = 1;
if (!raw)
*sizep = PAGE_SIZE;
+ zcache_zero_filled_pages--;
goto zero_fill;
}
@@ -923,6 +929,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
zero_filled = true;
zsize = 0;
zpages = 1;
+ zcache_zero_filled_pages--;
}
if (pampd_is_remote(pampd) && !zero_filled) {
--
1.7.7.6
Compression of zero-filled pages can unneccessarily cause internal
fragmentation, and thus waste memory. This special case can be
optimized.
This patch captures zero-filled pages, and marks their corresponding
zcache backing page entry as zero-filled. Whenever such zero-filled
page is retrieved, we fill the page frame with zero.
Acked-by: Dan Magenheimer <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
drivers/staging/zcache/zcache-main.c | 81 +++++++++++++++++++++++++++++++---
1 files changed, 75 insertions(+), 6 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index d73dd4b..6c35c7d 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -59,6 +59,12 @@ static inline void frontswap_tmem_exclusive_gets(bool b)
}
#endif
+/*
+ * mark pampd to special value in order that later
+ * retrieve will identify zero-filled pages
+ */
+#define ZERO_FILLED 0x2
+
/* enable (or fix code) when Seth's patches are accepted upstream */
#define zcache_writeback_enabled 0
@@ -543,7 +549,23 @@ static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
{
void *pampd = NULL, *cdata = data;
unsigned clen = size;
+ bool zero_filled = false;
struct page *page = (struct page *)(data), *newpage;
+ char *user_mem;
+
+ user_mem = kmap_atomic(page);
+
+ /*
+ * Compressing zero-filled pages will waste memory and introduce
+ * serious fragmentation, skip it to avoid overhead
+ */
+ if (page_is_zero_filled(user_mem)) {
+ kunmap_atomic(user_mem);
+ clen = 0;
+ zero_filled = true;
+ goto got_pampd;
+ }
+ kunmap_atomic(user_mem);
if (!raw) {
zcache_compress(page, &cdata, &clen);
@@ -592,6 +614,8 @@ got_pampd:
zcache_eph_zpages_max = zcache_eph_zpages;
if (ramster_enabled && raw)
ramster_count_foreign_pages(true, 1);
+ if (zero_filled)
+ pampd = (void *)ZERO_FILLED;
out:
return pampd;
}
@@ -601,14 +625,31 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
{
void *pampd = NULL, *cdata = data;
unsigned clen = size;
+ bool zero_filled = false;
struct page *page = (struct page *)(data), *newpage;
unsigned long zbud_mean_zsize;
unsigned long curr_pers_zpages, total_zsize;
+ char *user_mem;
if (data == NULL) {
BUG_ON(!ramster_enabled);
goto create_pampd;
}
+
+ user_mem = kmap_atomic(page);
+
+ /*
+ * Compressing zero-filled pages will waste memory and introduce
+ * serious fragmentation, skip it to avoid overhead
+ */
+ if (page_is_zero_filled(page)) {
+ kunmap_atomic(user_mem);
+ clen = 0;
+ zero_filled = true;
+ goto got_pampd;
+ }
+ kunmap_atomic(user_mem);
+
curr_pers_zpages = zcache_pers_zpages;
/* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */
if (!raw)
@@ -674,6 +715,8 @@ got_pampd:
zcache_pers_zbytes_max = zcache_pers_zbytes;
if (ramster_enabled && raw)
ramster_count_foreign_pages(false, 1);
+ if (zero_filled)
+ pampd = (void *)ZERO_FILLED;
out:
return pampd;
}
@@ -735,7 +778,8 @@ out:
*/
void zcache_pampd_create_finish(void *pampd, bool eph)
{
- zbud_create_finish((struct zbudref *)pampd, eph);
+ if (pampd != (void *)ZERO_FILLED)
+ zbud_create_finish((struct zbudref *)pampd, eph);
}
/*
@@ -780,6 +824,14 @@ static int zcache_pampd_get_data(char *data, size_t *sizep, bool raw,
BUG_ON(preemptible());
BUG_ON(eph); /* fix later if shared pools get implemented */
BUG_ON(pampd_is_remote(pampd));
+
+ if (pampd == (void *)ZERO_FILLED) {
+ handle_zero_filled_page(data);
+ if (!raw)
+ *sizep = PAGE_SIZE;
+ return 0;
+ }
+
if (raw)
ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
sizep, eph);
@@ -801,12 +853,21 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
struct tmem_oid *oid, uint32_t index)
{
int ret;
- bool eph = !is_persistent(pool);
+ bool eph = !is_persistent(pool), zero_filled = false;
struct page *page = NULL;
unsigned int zsize, zpages;
BUG_ON(preemptible());
BUG_ON(pampd_is_remote(pampd));
+
+ if (pampd == (void *)ZERO_FILLED) {
+ handle_zero_filled_page(data);
+ zero_filled = true;
+ if (!raw)
+ *sizep = PAGE_SIZE;
+ goto zero_fill;
+ }
+
if (raw)
ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
sizep, eph);
@@ -818,6 +879,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
}
page = zbud_free_and_delist((struct zbudref *)pampd, eph,
&zsize, &zpages);
+zero_fill:
if (eph) {
if (page)
zcache_eph_pageframes =
@@ -837,7 +899,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
}
if (!is_local_client(pool->client))
ramster_count_foreign_pages(eph, -1);
- if (page)
+ if (page && !zero_filled)
zcache_free_page(page);
return ret;
}
@@ -851,16 +913,23 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
{
struct page *page = NULL;
unsigned int zsize, zpages;
+ bool zero_filled = false;
BUG_ON(preemptible());
- if (pampd_is_remote(pampd)) {
+
+ if (pampd == (void *)ZERO_FILLED)
+ zero_filled = true;
+
+ if (pampd_is_remote(pampd) && !zero_filled) {
+
BUG_ON(!ramster_enabled);
pampd = ramster_pampd_free(pampd, pool, oid, index, acct);
if (pampd == NULL)
return;
}
if (is_ephemeral(pool)) {
- page = zbud_free_and_delist((struct zbudref *)pampd,
+ if (!zero_filled)
+ page = zbud_free_and_delist((struct zbudref *)pampd,
true, &zsize, &zpages);
if (page)
zcache_eph_pageframes =
@@ -883,7 +952,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
}
if (!is_local_client(pool->client))
ramster_count_foreign_pages(is_ephemeral(pool), -1);
- if (page)
+ if (page && !zero_filled)
zcache_free_page(page);
}
--
1.7.7.6
On Fri, Mar 15, 2013 at 10:34:18AM +0800, Wanpeng Li wrote:
> Increment/decrement zcache_[eph|pers]_zpages for zero-filled pages,
> the main point of the counters for zpages and pageframes is to be
> able to calculate density == zpages/pageframes. A zero-filled page
> becomes a zpage that "compresses" to zero bytes and, as a result,
> requires zero pageframes for storage. So the zpages counter should
> be increased but the pageframes counter should not.
>
> [Dan Magenheimer <[email protected]>: patch description]
> Acked-by: Dan Magenheimer <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> drivers/staging/zcache/zcache-main.c | 7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index 6c35c7d..ef8c960 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -863,6 +863,8 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
> if (pampd == (void *)ZERO_FILLED) {
> handle_zero_filled_page(data);
> zero_filled = true;
> + zsize = 0;
> + zpages = 1;
> if (!raw)
> *sizep = PAGE_SIZE;
> goto zero_fill;
> @@ -917,8 +919,11 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
>
> BUG_ON(preemptible());
>
> - if (pampd == (void *)ZERO_FILLED)
> + if (pampd == (void *)ZERO_FILLED) {
> zero_filled = true;
> + zsize = 0;
> + zpages = 1;
> + }
>
> if (pampd_is_remote(pampd) && !zero_filled) {
>
> --
> 1.7.7.6
>
On 03/15/2013 10:34 AM, Wanpeng Li wrote:
> Compression of zero-filled pages can unneccessarily cause internal
> fragmentation, and thus waste memory. This special case can be
> optimized.
>
> This patch captures zero-filled pages, and marks their corresponding
> zcache backing page entry as zero-filled. Whenever such zero-filled
> page is retrieved, we fill the page frame with zero.
>
> Acked-by: Dan Magenheimer <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> drivers/staging/zcache/zcache-main.c | 81 +++++++++++++++++++++++++++++++---
> 1 files changed, 75 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index d73dd4b..6c35c7d 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -59,6 +59,12 @@ static inline void frontswap_tmem_exclusive_gets(bool b)
> }
> #endif
>
> +/*
> + * mark pampd to special value in order that later
> + * retrieve will identify zero-filled pages
> + */
> +#define ZERO_FILLED 0x2
> +
> /* enable (or fix code) when Seth's patches are accepted upstream */
> #define zcache_writeback_enabled 0
>
> @@ -543,7 +549,23 @@ static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
> {
> void *pampd = NULL, *cdata = data;
> unsigned clen = size;
> + bool zero_filled = false;
> struct page *page = (struct page *)(data), *newpage;
> + char *user_mem;
> +
> + user_mem = kmap_atomic(page);
> +
> + /*
> + * Compressing zero-filled pages will waste memory and introduce
> + * serious fragmentation, skip it to avoid overhead
> + */
> + if (page_is_zero_filled(user_mem)) {
> + kunmap_atomic(user_mem);
> + clen = 0;
> + zero_filled = true;
> + goto got_pampd;
> + }
> + kunmap_atomic(user_mem);
>
> if (!raw) {
> zcache_compress(page, &cdata, &clen);
> @@ -592,6 +614,8 @@ got_pampd:
> zcache_eph_zpages_max = zcache_eph_zpages;
> if (ramster_enabled && raw)
> ramster_count_foreign_pages(true, 1);
> + if (zero_filled)
> + pampd = (void *)ZERO_FILLED;
> out:
> return pampd;
> }
> @@ -601,14 +625,31 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
> {
> void *pampd = NULL, *cdata = data;
> unsigned clen = size;
> + bool zero_filled = false;
> struct page *page = (struct page *)(data), *newpage;
> unsigned long zbud_mean_zsize;
> unsigned long curr_pers_zpages, total_zsize;
> + char *user_mem;
>
> if (data == NULL) {
> BUG_ON(!ramster_enabled);
> goto create_pampd;
> }
> +
> + user_mem = kmap_atomic(page);
> +
> + /*
> + * Compressing zero-filled pages will waste memory and introduce
> + * serious fragmentation, skip it to avoid overhead
> + */
> + if (page_is_zero_filled(page)) {
> + kunmap_atomic(user_mem);
> + clen = 0;
> + zero_filled = true;
> + goto got_pampd;
> + }
> + kunmap_atomic(user_mem);
> +
Maybe we can add a function for this code? It seems a bit duplicated.
> curr_pers_zpages = zcache_pers_zpages;
> /* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */
> if (!raw)
> @@ -674,6 +715,8 @@ got_pampd:
> zcache_pers_zbytes_max = zcache_pers_zbytes;
> if (ramster_enabled && raw)
> ramster_count_foreign_pages(false, 1);
> + if (zero_filled)
> + pampd = (void *)ZERO_FILLED;
> out:
> return pampd;
> }
> @@ -735,7 +778,8 @@ out:
> */
> void zcache_pampd_create_finish(void *pampd, bool eph)
> {
> - zbud_create_finish((struct zbudref *)pampd, eph);
> + if (pampd != (void *)ZERO_FILLED)
> + zbud_create_finish((struct zbudref *)pampd, eph);
> }
>
> /*
> @@ -780,6 +824,14 @@ static int zcache_pampd_get_data(char *data, size_t *sizep, bool raw,
> BUG_ON(preemptible());
> BUG_ON(eph); /* fix later if shared pools get implemented */
> BUG_ON(pampd_is_remote(pampd));
> +
> + if (pampd == (void *)ZERO_FILLED) {
> + handle_zero_filled_page(data);
> + if (!raw)
> + *sizep = PAGE_SIZE;
> + return 0;
> + }
> +
> if (raw)
> ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
> sizep, eph);
> @@ -801,12 +853,21 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
> struct tmem_oid *oid, uint32_t index)
> {
> int ret;
> - bool eph = !is_persistent(pool);
> + bool eph = !is_persistent(pool), zero_filled = false;
> struct page *page = NULL;
> unsigned int zsize, zpages;
>
> BUG_ON(preemptible());
> BUG_ON(pampd_is_remote(pampd));
> +
> + if (pampd == (void *)ZERO_FILLED) {
> + handle_zero_filled_page(data);
> + zero_filled = true;
> + if (!raw)
> + *sizep = PAGE_SIZE;
> + goto zero_fill;
> + }
> +
> if (raw)
> ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
> sizep, eph);
> @@ -818,6 +879,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
> }
> page = zbud_free_and_delist((struct zbudref *)pampd, eph,
> &zsize, &zpages);
> +zero_fill:
> if (eph) {
> if (page)
> zcache_eph_pageframes =
> @@ -837,7 +899,7 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
> }
> if (!is_local_client(pool->client))
> ramster_count_foreign_pages(eph, -1);
> - if (page)
> + if (page && !zero_filled)
> zcache_free_page(page);
> return ret;
> }
> @@ -851,16 +913,23 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
> {
> struct page *page = NULL;
> unsigned int zsize, zpages;
> + bool zero_filled = false;
>
> BUG_ON(preemptible());
> - if (pampd_is_remote(pampd)) {
> +
> + if (pampd == (void *)ZERO_FILLED)
> + zero_filled = true;
> +
> + if (pampd_is_remote(pampd) && !zero_filled) {
> +
> BUG_ON(!ramster_enabled);
> pampd = ramster_pampd_free(pampd, pool, oid, index, acct);
> if (pampd == NULL)
> return;
> }
> if (is_ephemeral(pool)) {
> - page = zbud_free_and_delist((struct zbudref *)pampd,
> + if (!zero_filled)
> + page = zbud_free_and_delist((struct zbudref *)pampd,
> true, &zsize, &zpages);
> if (page)
> zcache_eph_pageframes =
> @@ -883,7 +952,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
> }
> if (!is_local_client(pool->client))
> ramster_count_foreign_pages(is_ephemeral(pool), -1);
> - if (page)
> + if (page && !zero_filled)
> zcache_free_page(page);
> }
>
>
--
Regards,
-Bob
On Fri, Mar 15, 2013 at 10:34:15AM +0800, Wanpeng Li wrote:
> Changelog:
> v2 -> v3:
> * increment/decrement zcache_[eph|pers]_zpages for zero-filled pages, spotted by Dan
> * replace "zero" or "zero page" by "zero_filled_page", spotted by Dan
> v1 -> v2:
> * avoid changing tmem.[ch] entirely, spotted by Dan.
> * don't accumulate [eph|pers]pageframe and [eph|pers]zpages for
> zero-filled pages, spotted by Dan
> * cleanup TODO list
> * add Dan Acked-by.
In the future, please make the subject: lines have "staging: zcache:" in
them, so I don't have to edit them by hand.
thanks,
greg k-h
On Fri, Mar 15, 2013 at 10:34:17AM +0800, Wanpeng Li wrote:
> Compression of zero-filled pages can unneccessarily cause internal
> fragmentation, and thus waste memory. This special case can be
> optimized.
>
> This patch captures zero-filled pages, and marks their corresponding
> zcache backing page entry as zero-filled. Whenever such zero-filled
> page is retrieved, we fill the page frame with zero.
>
> Acked-by: Dan Magenheimer <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
This patch applies with a bunch of fuzz, meaning it wasn't made against
the latest tree, which worries me. Care to redo it, and the rest of the
series, and resend it?
thanks,
greg k-h