Re: [PATCH v3 2/5] zero-filled pages awareness
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 > Signed-off-by: Wanpeng Li 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 2/5] zero-filled pages awareness
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
> Signed-off-by: Wanpeng Li
> ---
> 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_r
[PATCH v3 2/5] zero-filled pages awareness
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
Signed-off-by: Wanpeng Li
---
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;
+
