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frontswap: s/put_page/store/g s/get_page/load

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Sounds so much more natural.

Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2012-05-15 11:32:15 -04:00
parent 839a1f79ed
commit 165c8aed5b
7 changed files with 76 additions and 76 deletions
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50
Documentation/vm/frontswap.txt
View File

@ -21,21 +21,21 @@ frontswap_ops funcs appropriately and the functions it provides must
conform to certain policies as follows:
An "init" prepares the device to receive frontswap pages associated
with the specified swap device number (aka "type"). A "put_page" will
with the specified swap device number (aka "type"). A "store" will
copy the page to transcendent memory and associate it with the type and
offset associated with the page. A "get_page" will copy the page, if found,
offset associated with the page. A "load" will copy the page, if found,
from transcendent memory into kernel memory, but will NOT remove the page
from from transcendent memory. An "invalidate_page" will remove the page
from transcendent memory and an "invalidate_area" will remove ALL pages
associated with the swap type (e.g., like swapoff) and notify the "device"
to refuse further puts with that swap type.
to refuse further stores with that swap type.
Once a page is successfully put, a matching get on the page will normally
Once a page is successfully stored, a matching load on the page will normally
succeed. So when the kernel finds itself in a situation where it needs
to swap out a page, it first attempts to use frontswap. If the put returns
to swap out a page, it first attempts to use frontswap. If the store returns
success, the data has been successfully saved to transcendent memory and
a disk write and, if the data is later read back, a disk read are avoided.
If a put returns failure, transcendent memory has rejected the data, and the
If a store returns failure, transcendent memory has rejected the data, and the
page can be written to swap as usual.
If a backend chooses, frontswap can be configured as a "writethrough
@ -44,18 +44,18 @@ in swap device writes is lost (and also a non-trivial performance advantage)
in order to allow the backend to arbitrarily "reclaim" space used to
store frontswap pages to more completely manage its memory usage.
Note that if a page is put and the page already exists in transcendent memory
(a "duplicate" put), either the put succeeds and the data is overwritten,
or the put fails AND the page is invalidated. This ensures stale data may
Note that if a page is stored and the page already exists in transcendent memory
(a "duplicate" store), either the store succeeds and the data is overwritten,
or the store fails AND the page is invalidated. This ensures stale data may
never be obtained from frontswap.
If properly configured, monitoring of frontswap is done via debugfs in
the /sys/kernel/debug/frontswap directory. The effectiveness of
frontswap can be measured (across all swap devices) with:
failed_puts - how many put attempts have failed
gets - how many gets were attempted (all should succeed)
succ_puts - how many put attempts have succeeded
failed_stores - how many store attempts have failed
loads - how many loads were attempted (all should succeed)
succ_stores - how many store attempts have succeeded
invalidates - how many invalidates were attempted
A backend implementation may provide additional metrics.
@ -125,7 +125,7 @@ nothingness and the only overhead is a few extra bytes per swapon'ed
swap device. If CONFIG_FRONTSWAP is enabled but no frontswap "backend"
registers, there is one extra global variable compared to zero for
every swap page read or written. If CONFIG_FRONTSWAP is enabled
AND a frontswap backend registers AND the backend fails every "put"
AND a frontswap backend registers AND the backend fails every "store"
request (i.e. provides no memory despite claiming it might),
CPU overhead is still negligible -- and since every frontswap fail
precedes a swap page write-to-disk, the system is highly likely
@ -159,13 +159,13 @@ entirely dynamic and random.
Whenever a swap-device is swapon'd frontswap_init() is called,
passing the swap device number (aka "type") as a parameter.
This notifies frontswap to expect attempts to "put" swap pages
This notifies frontswap to expect attempts to "store" swap pages
associated with that number.
Whenever the swap subsystem is readying a page to write to a swap
device (c.f swap_writepage()), frontswap_put_page is called. Frontswap
device (c.f swap_writepage()), frontswap_store is called. Frontswap
consults with the frontswap backend and if the backend says it does NOT
have room, frontswap_put_page returns -1 and the kernel swaps the page
have room, frontswap_store returns -1 and the kernel swaps the page
to the swap device as normal. Note that the response from the frontswap
backend is unpredictable to the kernel; it may choose to never accept a
page, it could accept every ninth page, or it might accept every
@ -177,7 +177,7 @@ corresponding to the page offset on the swap device to which it would
otherwise have written the data.
When the swap subsystem needs to swap-in a page (swap_readpage()),
it first calls frontswap_get_page() which checks the frontswap_map to
it first calls frontswap_load() which checks the frontswap_map to
see if the page was earlier accepted by the frontswap backend. If
it was, the page of data is filled from the frontswap backend and
the swap-in is complete. If not, the normal swap-in code is
@ -185,7 +185,7 @@ executed to obtain the page of data from the real swap device.
So every time the frontswap backend accepts a page, a swap device read
and (potentially) a swap device write are replaced by a "frontswap backend
put" and (possibly) a "frontswap backend get", which are presumably much
store" and (possibly) a "frontswap backend loads", which are presumably much
faster.
4) Can't frontswap be configured as a "special" swap device that is
@ -215,8 +215,8 @@ that are inappropriate for a RAM-oriented device including delaying
the write of some pages for a significant amount of time. Synchrony is
required to ensure the dynamicity of the backend and to avoid thorny race
conditions that would unnecessarily and greatly complicate frontswap
and/or the block I/O subsystem. That said, only the initial "put"
and "get" operations need be synchronous. A separate asynchronous thread
and/or the block I/O subsystem. That said, only the initial "store"
and "load" operations need be synchronous. A separate asynchronous thread
is free to manipulate the pages stored by frontswap. For example,
the "remotification" thread in RAMster uses standard asynchronous
kernel sockets to move compressed frontswap pages to a remote machine.
@ -229,7 +229,7 @@ choose to accept pages only until host-swapping might be imminent,
then force guests to do their own swapping.
There is a downside to the transcendent memory specifications for
frontswap: Since any "put" might fail, there must always be a real
frontswap: Since any "store" might fail, there must always be a real
slot on a real swap device to swap the page. Thus frontswap must be
implemented as a "shadow" to every swapon'd device with the potential
capability of holding every page that the swap device might have held
@ -240,16 +240,16 @@ installation, frontswap is useless. Swapless portable devices
can still use frontswap but a backend for such devices must configure
some kind of "ghost" swap device and ensure that it is never used.
5) Why this weird definition about "duplicate puts"? If a page
has been previously successfully put, can't it always be
5) Why this weird definition about "duplicate stores"? If a page
has been previously successfully stored, can't it always be
successfully overwritten?
Nearly always it can, but no, sometimes it cannot. Consider an example
where data is compressed and the original 4K page has been compressed
to 1K. Now an attempt is made to overwrite the page with data that
is non-compressible and so would take the entire 4K. But the backend
has no more space. In this case, the put must be rejected. Whenever
frontswap rejects a put that would overwrite, it also must invalidate
has no more space. In this case, the store must be rejected. Whenever
frontswap rejects a store that would overwrite, it also must invalidate
the old data and ensure that it is no longer accessible. Since the
swap subsystem then writes the new data to the read swap device,
this is the correct course of action to ensure coherency.

8
drivers/staging/ramster/zcache-main.c
View File

@ -3002,7 +3002,7 @@ static inline struct tmem_oid oswiz(unsigned type, u32 ind)
return oid;
}
static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
static int zcache_frontswap_store(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -3025,7 +3025,7 @@ static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
/* returns 0 if the page was successfully gotten from frontswap, -1 if
* was not present (should never happen!) */
static int zcache_frontswap_get_page(unsigned type, pgoff_t offset,
static int zcache_frontswap_load(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -3080,8 +3080,8 @@ static void zcache_frontswap_init(unsigned ignored)
}
static struct frontswap_ops zcache_frontswap_ops = {
.put_page = zcache_frontswap_put_page,
.get_page = zcache_frontswap_get_page,
.store = zcache_frontswap_store,
.load = zcache_frontswap_load,
.invalidate_page = zcache_frontswap_flush_page,
.invalidate_area = zcache_frontswap_flush_area,
.init = zcache_frontswap_init

10
drivers/staging/zcache/zcache-main.c
View File

@ -1835,7 +1835,7 @@ static int zcache_frontswap_poolid = -1;
* Swizzling increases objects per swaptype, increasing tmem concurrency
* for heavy swaploads. Later, larger nr_cpus -> larger SWIZ_BITS
* Setting SWIZ_BITS to 27 basically reconstructs the swap entry from
* frontswap_get_page(), but has side-effects. Hence using 8.
* frontswap_load(), but has side-effects. Hence using 8.
*/
#define SWIZ_BITS 8
#define SWIZ_MASK ((1 << SWIZ_BITS) - 1)
@ -1849,7 +1849,7 @@ static inline struct tmem_oid oswiz(unsigned type, u32 ind)
return oid;
}
static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
static int zcache_frontswap_store(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -1870,7 +1870,7 @@ static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
/* returns 0 if the page was successfully gotten from frontswap, -1 if
* was not present (should never happen!) */
static int zcache_frontswap_get_page(unsigned type, pgoff_t offset,
static int zcache_frontswap_load(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -1919,8 +1919,8 @@ static void zcache_frontswap_init(unsigned ignored)
}
static struct frontswap_ops zcache_frontswap_ops = {
.put_page = zcache_frontswap_put_page,
.get_page = zcache_frontswap_get_page,
.store = zcache_frontswap_store,
.load = zcache_frontswap_load,
.invalidate_page = zcache_frontswap_flush_page,
.invalidate_area = zcache_frontswap_flush_area,
.init = zcache_frontswap_init

8
drivers/xen/tmem.c
View File

@ -269,7 +269,7 @@ static inline struct tmem_oid oswiz(unsigned type, u32 ind)
}
/* returns 0 if the page was successfully put into frontswap, -1 if not */
static int tmem_frontswap_put_page(unsigned type, pgoff_t offset,
static int tmem_frontswap_store(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -295,7 +295,7 @@ static int tmem_frontswap_put_page(unsigned type, pgoff_t offset,
* returns 0 if the page was successfully gotten from frontswap, -1 if
* was not present (should never happen!)
*/
static int tmem_frontswap_get_page(unsigned type, pgoff_t offset,
static int tmem_frontswap_load(unsigned type, pgoff_t offset,
struct page *page)
{
u64 ind64 = (u64)offset;
@ -362,8 +362,8 @@ static int __init no_frontswap(char *s)
__setup("nofrontswap", no_frontswap);
static struct frontswap_ops __initdata tmem_frontswap_ops = {
.put_page = tmem_frontswap_put_page,
.get_page = tmem_frontswap_get_page,
.store = tmem_frontswap_store,
.load = tmem_frontswap_load,
.invalidate_page = tmem_frontswap_flush_page,
.invalidate_area = tmem_frontswap_flush_area,
.init = tmem_frontswap_init

16
include/linux/frontswap.h
View File

@ -7,8 +7,8 @@
struct frontswap_ops {
void (*init)(unsigned);
int (*put_page)(unsigned, pgoff_t, struct page *);
int (*get_page)(unsigned, pgoff_t, struct page *);
int (*store)(unsigned, pgoff_t, struct page *);
int (*load)(unsigned, pgoff_t, struct page *);
void (*invalidate_page)(unsigned, pgoff_t);
void (*invalidate_area)(unsigned);
};
@ -21,8 +21,8 @@ extern unsigned long frontswap_curr_pages(void);
extern void frontswap_writethrough(bool);
extern void __frontswap_init(unsigned type);
extern int __frontswap_put_page(struct page *page);
extern int __frontswap_get_page(struct page *page);
extern int __frontswap_store(struct page *page);
extern int __frontswap_load(struct page *page);
extern void __frontswap_invalidate_page(unsigned, pgoff_t);
extern void __frontswap_invalidate_area(unsigned);
@ -88,21 +88,21 @@ static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
}
#endif
static inline int frontswap_put_page(struct page *page)
static inline int frontswap_store(struct page *page)
{
int ret = -1;
if (frontswap_enabled)
ret = __frontswap_put_page(page);
ret = __frontswap_store(page);
return ret;
}
static inline int frontswap_get_page(struct page *page)
static inline int frontswap_load(struct page *page)
{
int ret = -1;
if (frontswap_enabled)
ret = __frontswap_get_page(page);
ret = __frontswap_load(page);
return ret;
}

56
mm/frontswap.c
View File

@ -39,7 +39,7 @@ bool frontswap_enabled __read_mostly;
EXPORT_SYMBOL(frontswap_enabled);
/*
* If enabled, frontswap_put will return failure even on success. As
* If enabled, frontswap_store will return failure even on success. As
* a result, the swap subsystem will always write the page to swap, in
* effect converting frontswap into a writethrough cache. In this mode,
* there is no direct reduction in swap writes, but a frontswap backend
@ -54,27 +54,27 @@ static bool frontswap_writethrough_enabled __read_mostly;
* properly configured). These are for information only so are not protected
* against increment races.
*/
static u64 frontswap_gets;
static u64 frontswap_succ_puts;
static u64 frontswap_failed_puts;
static u64 frontswap_loads;
static u64 frontswap_succ_stores;
static u64 frontswap_failed_stores;
static u64 frontswap_invalidates;
static inline void inc_frontswap_gets(void) {
frontswap_gets++;
static inline void inc_frontswap_loads(void) {
frontswap_loads++;
}
static inline void inc_frontswap_succ_puts(void) {
frontswap_succ_puts++;
static inline void inc_frontswap_succ_stores(void) {
frontswap_succ_stores++;
}
static inline void inc_frontswap_failed_puts(void) {
frontswap_failed_puts++;
static inline void inc_frontswap_failed_stores(void) {
frontswap_failed_stores++;
}
static inline void inc_frontswap_invalidates(void) {
frontswap_invalidates++;
}
#else
static inline void inc_frontswap_gets(void) { }
static inline void inc_frontswap_succ_puts(void) { }
static inline void inc_frontswap_failed_puts(void) { }
static inline void inc_frontswap_loads(void) { }
static inline void inc_frontswap_succ_stores(void) { }
static inline void inc_frontswap_failed_stores(void) { }
static inline void inc_frontswap_invalidates(void) { }
#endif
/*
@ -116,13 +116,13 @@ void __frontswap_init(unsigned type)
EXPORT_SYMBOL(__frontswap_init);
/*
* "Put" data from a page to frontswap and associate it with the page's
* "Store" data from a page to frontswap and associate it with the page's
* swaptype and offset. Page must be locked and in the swap cache.
* If frontswap already contains a page with matching swaptype and
* offset, the frontswap implmentation may either overwrite the data and
* return success or invalidate the page from frontswap and return failure.
*/
int __frontswap_put_page(struct page *page)
int __frontswap_store(struct page *page)
{
int ret = -1, dup = 0;
swp_entry_t entry = { .val = page_private(page), };
@ -134,10 +134,10 @@ int __frontswap_put_page(struct page *page)
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
dup = 1;
ret = (*frontswap_ops.put_page)(type, offset, page);
ret = (*frontswap_ops.store)(type, offset, page);
if (ret == 0) {
frontswap_set(sis, offset);
inc_frontswap_succ_puts();
inc_frontswap_succ_stores();
if (!dup)
atomic_inc(&sis->frontswap_pages);
} else if (dup) {
@ -147,22 +147,22 @@ int __frontswap_put_page(struct page *page)
*/
frontswap_clear(sis, offset);
atomic_dec(&sis->frontswap_pages);
inc_frontswap_failed_puts();
inc_frontswap_failed_stores();
} else
inc_frontswap_failed_puts();
inc_frontswap_failed_stores();
if (frontswap_writethrough_enabled)
/* report failure so swap also writes to swap device */
ret = -1;
return ret;
}
EXPORT_SYMBOL(__frontswap_put_page);
EXPORT_SYMBOL(__frontswap_store);
/*
* "Get" data from frontswap associated with swaptype and offset that were
* specified when the data was put to frontswap and use it to fill the
* specified page with data. Page must be locked and in the swap cache.
*/
int __frontswap_get_page(struct page *page)
int __frontswap_load(struct page *page)
{
int ret = -1;
swp_entry_t entry = { .val = page_private(page), };
@ -173,12 +173,12 @@ int __frontswap_get_page(struct page *page)
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
ret = (*frontswap_ops.get_page)(type, offset, page);
ret = (*frontswap_ops.load)(type, offset, page);
if (ret == 0)
inc_frontswap_gets();
inc_frontswap_loads();
return ret;
}
EXPORT_SYMBOL(__frontswap_get_page);
EXPORT_SYMBOL(__frontswap_load);
/*
* Invalidate any data from frontswap associated with the specified swaptype
@ -301,10 +301,10 @@ static int __init init_frontswap(void)
struct dentry *root = debugfs_create_dir("frontswap", NULL);
if (root == NULL)
return -ENXIO;
debugfs_create_u64("gets", S_IRUGO, root, &frontswap_gets);
debugfs_create_u64("succ_puts", S_IRUGO, root, &frontswap_succ_puts);
debugfs_create_u64("failed_puts", S_IRUGO, root,
&frontswap_failed_puts);
debugfs_create_u64("loads", S_IRUGO, root, &frontswap_loads);
debugfs_create_u64("succ_stores", S_IRUGO, root, &frontswap_succ_stores);
debugfs_create_u64("failed_stores", S_IRUGO, root,
&frontswap_failed_stores);
debugfs_create_u64("invalidates", S_IRUGO,
root, &frontswap_invalidates);
#endif

4
mm/page_io.c
View File

@ -99,7 +99,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
unlock_page(page);
goto out;
}
if (frontswap_put_page(page) == 0) {
if (frontswap_store(page) == 0) {
set_page_writeback(page);
unlock_page(page);
end_page_writeback(page);
@ -129,7 +129,7 @@ int swap_readpage(struct page *page)
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageUptodate(page));
if (frontswap_get_page(page) == 0) {
if (frontswap_load(page) == 0) {
SetPageUptodate(page);
unlock_page(page);
goto out;