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staging: zcache: 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 <dan.magenheimer@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Wanpeng Li 2013-04-02 10:46:14 +08:00 committed by Greg Kroah-Hartman
parent bdcde42d74
commit 8762c7dde7
1 changed files with 70 additions and 13 deletions
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77
drivers/staging/zcache/zcache-main.c
View File

@ -61,6 +61,12 @@ 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
@ -277,17 +283,23 @@ 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)
/*
* Compressing zero-filled pages will waste memory and introduce
* serious fragmentation, skip it to avoid overhead.
*/
static bool page_is_zero_filled(struct page *p)
{
unsigned int pos;
unsigned long *page;
page = (unsigned long *)ptr;
char *page;
page = kmap_atomic(p);
for (pos = 0; pos < PAGE_SIZE / sizeof(*page); pos++) {
if (page[pos])
if (page[pos]) {
kunmap_atomic(page);
return false;
}
}
kunmap_atomic(page);
return true;
}
@ -356,8 +368,15 @@ 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;
if (page_is_zero_filled(page)) {
clen = 0;
zero_filled = true;
goto got_pampd;
}
if (!raw) {
zcache_compress(page, &cdata, &clen);
if (clen > zbud_max_buddy_size()) {
@ -397,6 +416,8 @@ got_pampd:
inc_zcache_eph_zpages();
if (ramster_enabled && raw)
ramster_count_foreign_pages(true, 1);
if (zero_filled)
pampd = (void *)ZERO_FILLED;
out:
return pampd;
}
@ -406,6 +427,7 @@ 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;
@ -414,6 +436,13 @@ static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
BUG_ON(!ramster_enabled);
goto create_pampd;
}
if (page_is_zero_filled(page)) {
clen = 0;
zero_filled = true;
goto got_pampd;
}
curr_pers_zpages = zcache_pers_zpages;
/* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */
if (!raw)
@ -471,6 +500,8 @@ got_pampd:
inc_zcache_pers_zbytes(clen);
if (ramster_enabled && raw)
ramster_count_foreign_pages(false, 1);
if (zero_filled)
pampd = (void *)ZERO_FILLED;
out:
return pampd;
}
@ -532,6 +563,7 @@ out:
*/
void zcache_pampd_create_finish(void *pampd, bool eph)
{
if (pampd != (void *)ZERO_FILLED)
zbud_create_finish((struct zbudref *)pampd, eph);
}
@ -577,6 +609,14 @@ 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);
@ -597,13 +637,22 @@ static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
void *pampd, struct tmem_pool *pool,
struct tmem_oid *oid, uint32_t index)
{
int ret;
bool eph = !is_persistent(pool);
int ret = 0;
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);
@ -615,6 +664,7 @@ 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)
dec_zcache_eph_pageframes();
@ -628,7 +678,7 @@ 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;
}
@ -642,15 +692,21 @@ 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)) {
if (!zero_filled)
page = zbud_free_and_delist((struct zbudref *)pampd,
true, &zsize, &zpages);
if (page)
@ -659,6 +715,7 @@ static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
dec_zcache_eph_zbytes(zsize);
/* FIXME CONFIG_RAMSTER... check acct parameter? */
} else {
if (!zero_filled)
page = zbud_free_and_delist((struct zbudref *)pampd,
false, &zsize, &zpages);
if (page)
@ -668,7 +725,7 @@ 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);
}