by yunfeng zhang

[permalink] [raw]

Subject: Re: [PATCH 2.6.16.29 1/1] memory: enhance Linux swap subsystem

A new patch has been done by me, based on the previous quilt patch
(2.6.16.29). Here is
changelog

--------------------------
>> NEW
New kernel thread kppsd is added to execute background scanning task
periodically (mm/vmscan.c).

PPS statistic is added into /proc/meminfo, its prototype is in
include/linux/mm.h.

Documentation/vm_pps.txt is also updated to show the aboved two new features,
some sections is re-written for comprehension.

>> BUG
New loop code is introduced in shrink_private_vma (mm/vmscan.c) and
pps_swapoff (mm/swapfile.c), contrast with old code, even lhtemp is freed
during loop, it's also safe.

A bug is catched in mm/memory.c:zap_pte_range -- if a PrivatePage is
being written back, it will be migrated back to Linux legacy page system.

A fault done by me in previous patch is remedied in stage 5, now stage 5 can
work.

>> MISCELLANEOUS
UP code has been separated from SMP code in dftlb.
--------------------------

Index: linux-2.6.16.29/Documentation/vm_pps.txt
===================================================================
--- linux-2.6.16.29.orig/Documentation/vm_pps.txt 2007-01-04
14:47:35.000000000 +0800
+++ linux-2.6.16.29/Documentation/vm_pps.txt 2007-01-04 14:49:36.000000000 +0800
@@ -6,11 +6,11 @@
// Purpose <([{
The file is used to document the idea which is published firstly at
http://www.ussg.iu.edu/hypermail/linux/kernel/0607.2/0451.html, as a part of my
-OS -- main page http://blog.chinaunix.net/u/21764/index.php. In brief, a patch
-of the document to enchance the performance of Linux swap subsystem. You can
-find the overview of the idea in section <How to Reclaim Pages more
-Efficiently> and how I patch it into Linux 2.6.16.29 in section <Pure Private
-Page System -- pps>.
+OS -- main page http://blog.chinaunix.net/u/21764/index.php. In brief, the
+patch of the document is for enchancing the performance of Linux swap
+subsystem. You can find the overview of the idea in section <How to Reclaim
+Pages more Efficiently> and how I patch it into Linux 2.6.16.29 in section
+<Pure Private Page System -- pps>.
// }])>

// How to Reclaim Pages more Efficiently <([{
@@ -21,7 +21,9 @@
OK! to modern OS, its memory subsystem can be divided into three layers
1) Space layer (InodeSpace, UserSpace and CoreSpace).
2) VMA layer (PrivateVMA and SharedVMA, memory architecture-independent layer).
-3) PTE and page layer (architecture-dependent).
+3) PTE, zone/memory inode layer (architecture-dependent).
+4) Maybe it makes you sense that Page should be placed on the 3rd layer, but
+ here, it's placed on the 2nd layer since it's the basic unit of VMA.

Since the 2nd layer assembles the much statistic of page-acess information, so
it's nature that swap subsystem should be deployed and implemented on the 2nd
@@ -41,7 +43,8 @@
Unfortunately, Linux 2.6.16.29 swap subsystem is based on the 3rd layer -- a
system on zone::active_list/inactive_list.

-I've finished a patch, see section <Pure Private Page System -- pps>.
Note, it ISN'T perfect.
+I've finished a patch, see section <Pure Private Page System -- pps>. Note, it
+ISN'T perfect.
// }])>

// Pure Private Page System -- pps <([{
@@ -70,7 +73,18 @@
3) <Private Page Lifecycle of pps> -- how private pages enter in/go off pps.
4) <VMA Lifecycle of pps> which VMA is belonging to pps.

-PPS uses init_mm.mm_list list to enumerate all swappable UserSpace.
+PPS uses init_mm.mm_list list to enumerate all swappable UserSpace
+(shrink_private_vma).
+
+A new kernel thread -- kppsd is introduced in mm/vmscan.c, its task is to
+execute the stages of pps periodically, note an appropriate timeout ticks is
+necessary so we can give application a chance to re-map back its PrivatePage
+from UnmappedPTE to PTE, that is, show their conglomeration affinity.
+scan_control::pps_cmd field is used to control the behavior of kppsd, = 1 for
+accelerating scanning process and reclaiming pages, it's used in balance_pgdat.
+
+PPS statistic data is appended to /proc/meminfo entry, its prototype is in
+include/linux/mm.h.

I'm also glad to highlight my a new idea -- dftlb which is described in
section <Delay to Flush TLB>.
@@ -97,15 +111,19 @@
gone when a CPU starts to execute the task in timer interrupt, so don't use
dftlb.
combine stage 1 with stage 2, and send IPI immediately in fill_in_tlb_tasks.
+
+dftlb increases mm_struct::mm_users to prevent the mm from being freed when
+other CPU works on it.
// }])>

// Stage Definition <([{
The whole process of private page page-out is divided into six stages, as
-showed in shrink_pvma_scan_ptes of mm/vmscan.c
+showed in shrink_pvma_scan_ptes of mm/vmscan.c, the code groups the similar
+pages to a series.
1) PTE to untouched PTE (access bit is cleared), append flushing
tasks to dftlb.
2) Convert untouched PTE to UnmappedPTE.
3) Link SwapEntry to every UnmappedPTE.
-4) Synchronize the page of a UnmappedPTE with its physical swap page.
+4) Flush PrivatePage of UnmappedPTE to its disk SwapPage.
5) Reclaimed the page and shift UnmappedPTE to SwappedPTE.
6) SwappedPTE stage.
// }])>
@@ -114,7 +132,15 @@
New VMA flag (VM_PURE_PRIVATE) is appended into VMA in include/linux/mm.h.

New PTE type (UnmappedPTE) is appended into PTE system in
-include/asm-i386/pgtable.h.
+include/asm-i386/pgtable.h. Its prototype is
+struct UnmappedPTE {
+ int present : 1; // must be 0.
+ ...
+ int pageNum : 20;
+};
+The new PTE has a feature, it keeps a link to its PrivatePage and prevent the
+page from being visited by CPU, so you can use it in <Stage Definition> as a
+middleware.
// }])>

// Concurrent Racers of Shrinking pps <([{
@@ -125,10 +151,14 @@
1) mm/swapfile.c pps_swapoff (swapoff API).
2) mm/memory.c do_wp_page, handle_pte_fault::unmapped_pte, do_anonymous_page
(page-fault).
+
+The VMAs of pps can coexist with madvise, mlock, mprotect, mmap and munmap,
+that is why new VMA created from mmap.c:split_vma can re-enter into pps.
// }])>

// Private Page Lifecycle of pps <([{
-All pages belonging to pps are called as pure private page.
+All pages belonging to pps are called as pure private page, its PTE type is PTE
+or UnmappedPTE.

IN (NOTE, when a pure private page enters into pps, it's also trimmed from
Linux legacy page system by commeting lru_cache_add_active clause)
@@ -147,9 +177,10 @@
// }])>

// VMA Lifecycle of pps <([{
-When a PrivateVMA enters into pps, it's or-ed a new flag -- VM_PURE_PRIVATE,
-the flag is used in the shrink_private_vma of mm/vmscan.c. Other fields are
-left untouched.
+When a PrivateVMA enters into pps, it's or-ed a new flag -- VM_PURE_PRIVATE in
+memory.c:enter_pps, you can also find which VMA is fit with pps in it, the flag
+is used in the shrink_private_vma of mm/vmscan.c. Other fields are left
+untouched.

IN.
1) fs/exec.c setup_arg_pages (StackVMA).
@@ -173,18 +204,9 @@
UnmappedPTE) and PrivatePage (SwapPage) which is described in my OS and the
aboved hyperlink of Linux kernel mail list. So it's a compromise to use
Linux legacy SwapCache in my pps.
-2) SwapCache should provide more flexible interfaces, shrink_pvma_scan_ptes
+2) SwapSpace should provide more flexible interfaces, shrink_pvma_scan_ptes
need allocate swap entries in batch, exactly, allocate a batch of fake
continual swap entries, see mm/pps_swapin_readahead.
-3) pps statistic entry in /proc/meminfo.
-4) a better arithmetic to pick mm out to scan and shrink in shrink_private_vma.
-5) It's better to execute the first 2 stages when system is idle, current
- SwapDaemon only is activated when free pages are low.
-6) A scanning count should be added into mm_struct, so when the count is
- becoming enough old to open stage 3 and 4.
-
-I'm still working on improvement 4, 5 and 6 to find out how to maximum the
-performance of swap subsystem.

If Linux kernel group can't make a schedule to re-write their memory code,
however, pps maybe is the best solution until now.
Index: linux-2.6.16.29/fs/exec.c
===================================================================
--- linux-2.6.16.29.orig/fs/exec.c 2007-01-04 14:47:35.000000000 +0800
+++ linux-2.6.16.29/fs/exec.c 2007-01-04 14:49:36.000000000 +0800
@@ -320,6 +320,8 @@
pte_unmap_unlock(pte, ptl);
goto out;
}
+ atomic_inc(&pps_info.total);
+ atomic_inc(&pps_info.pte_count);
inc_mm_counter(mm, anon_rss);
set_pte_at(mm, address, pte, pte_mkdirty(pte_mkwrite(mk_pte(
page, vma->vm_page_prot))));
Index: linux-2.6.16.29/fs/proc/proc_misc.c
===================================================================
--- linux-2.6.16.29.orig/fs/proc/proc_misc.c 2007-01-04 14:47:35.000000000 +0800
+++ linux-2.6.16.29/fs/proc/proc_misc.c 2007-01-04 14:49:36.000000000 +0800
@@ -174,7 +174,11 @@
"PageTables: %8lu kB\n"
"VmallocTotal: %8lu kB\n"
"VmallocUsed: %8lu kB\n"
- "VmallocChunk: %8lu kB\n",
+ "VmallocChunk: %8lu kB\n"
+ "PPS Total: %8d kB\n"
+ "PPS PTE: %8d kB\n"
+ "PPS Unmapped: %8d kB\n"
+ "PPS Swapped: %8d kB\n",
K(i.totalram),
K(i.freeram),
K(i.bufferram),
@@ -197,7 +201,11 @@
K(ps.nr_page_table_pages),
(unsigned long)VMALLOC_TOTAL >> 10,
vmi.used >> 10,
- vmi.largest_chunk >> 10
+ vmi.largest_chunk >> 10,
+ K(pps_info.total.counter),
+ K(pps_info.pte_count.counter),
+ K(pps_info.unmapped_count.counter),
+ K(pps_info.swapped_count.counter)
);

len += hugetlb_report_meminfo(page + len);
Index: linux-2.6.16.29/include/asm-i386/mmu_context.h
===================================================================
--- linux-2.6.16.29.orig/include/asm-i386/mmu_context.h 2007-01-04
14:47:35.000000000 +0800
+++ linux-2.6.16.29/include/asm-i386/mmu_context.h 2007-01-04
14:49:36.000000000 +0800
@@ -33,6 +33,9 @@
/* stop flush ipis for the previous mm */
cpu_clear(cpu, prev->cpu_vm_mask);
#ifdef CONFIG_SMP
+ // vmscan.c::end_tlb_tasks maybe had copied cpu_vm_mask before we leave
+ // prev, so let's flush the trace of prev of delay_tlb_tasks.
+ timer_flush_tlb_tasks(NULL);
per_cpu(cpu_tlbstate, cpu).state = TLBSTATE_OK;
per_cpu(cpu_tlbstate, cpu).active_mm = next;
#endif
Index: linux-2.6.16.29/include/linux/mm.h
===================================================================
--- linux-2.6.16.29.orig/include/linux/mm.h 2007-01-04 14:47:36.000000000 +0800
+++ linux-2.6.16.29/include/linux/mm.h 2007-01-04 14:49:37.000000000 +0800
@@ -1058,8 +1058,16 @@
extern int randomize_va_space;
#endif

+struct pps_info {
+ atomic_t total;
+ atomic_t pte_count; // stage 1 and 2.
+ atomic_t unmapped_count; // stage 3 and 4.
+ atomic_t swapped_count; // stage 6.
+};
+extern struct pps_info pps_info;
+
/* vmscan.c::delay flush TLB */
-struct delay_tlb_task_t
+struct delay_tlb_task
{
struct mm_struct* mm;
cpumask_t cpu_mask;
@@ -1067,7 +1075,7 @@
unsigned long start[32];
unsigned long end[32];
};
-extern struct delay_tlb_task_t delay_tlb_tasks[32];
+extern struct delay_tlb_task delay_tlb_tasks[32];

// The prototype of the function is fit with the "func" of "int
// smp_call_function (void (*func) (void *info), void *info, int retry, int
Index: linux-2.6.16.29/kernel/timer.c
===================================================================
--- linux-2.6.16.29.orig/kernel/timer.c 2007-01-04 14:47:37.000000000 +0800
+++ linux-2.6.16.29/kernel/timer.c 2007-01-04 14:49:37.000000000 +0800
@@ -843,7 +843,9 @@
scheduler_tick();
run_posix_cpu_timers(p);

+#ifdef SMP
timer_flush_tlb_tasks(NULL);
+#endif
}

/*
Index: linux-2.6.16.29/mm/memory.c
===================================================================
--- linux-2.6.16.29.orig/mm/memory.c 2007-01-04 14:47:37.000000000 +0800
+++ linux-2.6.16.29/mm/memory.c 2007-01-04 14:49:37.000000000 +0800
@@ -615,6 +615,9 @@
spinlock_t *ptl;
int file_rss = 0;
int anon_rss = 0;
+ int pps_pte = 0;
+ int pps_unmapped = 0;
+ int pps_swapped = 0;

pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
do {
@@ -658,8 +661,13 @@
addr) != page->index)
set_pte_at(mm, addr, pte,
pgoff_to_pte(page->index));
- // if (vma->vm_flags & VM_PURE_PRIVATE && page != ZERO_PAGE(addr))
- // lru_cache_add_active(page);
+ if (vma->vm_flags & VM_PURE_PRIVATE) {
+ if (page != ZERO_PAGE(addr)) {
+ if (PageWriteback(page))
+ lru_cache_add_active(page);
+ pps_pte++;
+ }
+ }
if (PageAnon(page))
anon_rss--;
else {
@@ -682,18 +690,28 @@
if (pte_unmapped(ptent)) {
struct page *page;
page = pfn_to_page(pte_pfn(ptent));
+ BUG_ON(page == ZERO_PAGE(addr));
+ if (PageWriteback(page))
+ lru_cache_add_active(page);
+ pps_unmapped++;
pte_clear_full(mm, addr, pte, tlb->fullmm);
- // lru_cache_add_active(page);
tlb_remove_page(tlb, page);
anon_rss--;
continue;
}
- if (pte_swapped(ptent))
+ if (pte_swapped(ptent)) {
+ if (vma->vm_flags & VM_PURE_PRIVATE)
+ pps_swapped++;
free_swap_and_cache(pte_to_swp_entry(ptent));
+ }
pte_clear_full(mm, addr, pte, tlb->fullmm);
} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));

add_mm_rss(mm, file_rss, anon_rss);
+ atomic_sub(pps_pte + pps_unmapped, &pps_info.total);
+ atomic_sub(pps_pte, &pps_info.pte_count);
+ atomic_sub(pps_unmapped, &pps_info.unmapped_count);
+ atomic_sub(pps_swapped, &pps_info.swapped_count);
pte_unmap_unlock(pte - 1, ptl);

return addr;
@@ -1521,6 +1539,10 @@
lazy_mmu_prot_update(entry);
if (!(vma->vm_flags & VM_PURE_PRIVATE))
lru_cache_add_active(new_page);
+ else {
+ atomic_inc(&pps_info.total);
+ atomic_inc(&pps_info.pte_count);
+ }
page_add_new_anon_rmap(new_page, vma, address);

/* Free the old page.. */
@@ -2041,6 +2063,11 @@
if (vm_swap_full())
remove_exclusive_swap_page(page);
unlock_page(page);
+ if (vma->vm_flags & VM_PURE_PRIVATE) {
+ atomic_dec(&pps_info.swapped_count);
+ atomic_inc(&pps_info.total);
+ atomic_inc(&pps_info.pte_count);
+ }

if (write_access) {
if (do_wp_page(mm, vma, address,
@@ -2094,6 +2121,10 @@
goto release;
if (!(vma->vm_flags & VM_PURE_PRIVATE))
lru_cache_add_active(page);
+ else {
+ atomic_inc(&pps_info.total);
+ atomic_inc(&pps_info.pte_count);
+ }
inc_mm_counter(mm, anon_rss);
page_add_new_anon_rmap(page, vma, address);
} else {
@@ -2311,6 +2342,8 @@
if (!pte_present(entry)) {
if (pte_unmapped(entry)) {
BUG_ON(!(vma->vm_flags & VM_PURE_PRIVATE));
+ atomic_dec(&pps_info.unmapped_count);
+ atomic_inc(&pps_info.pte_count);
struct page* page = pte_page(entry);
pte_t temp_pte = mk_pte(page, vma->vm_page_prot);
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
@@ -2565,8 +2598,11 @@
{
struct page* page;
pte_t entry;
- pte_t* pte;
+ pte_t *pte;
spinlock_t* ptl;
+ int pps_pte = 0;
+ int pps_unmapped = 0;
+ int pps_swapped = 0;

pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
do {
@@ -2577,16 +2613,23 @@
set_pte_at(mm, addr, pte, entry);
BUG_ON(page == ZERO_PAGE(addr));
page_add_new_anon_rmap(page, vma, addr);
- }
- if (pte_present(*pte)) {
+ lru_cache_add_active(page);
+ pps_unmapped++;
+ } else if (pte_present(*pte)) {
page = pte_page(*pte);
if (page == ZERO_PAGE(addr))
continue;
lru_cache_add_active(page);
- }
+ pps_pte++;
+ } else if (!pte_present(*pte) && pte_swapped(*pte))
+ pps_swapped++;
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap_unlock(pte - 1, ptl);
lru_add_drain();
+ atomic_sub(pps_pte + pps_unmapped, &pps_info.total);
+ atomic_sub(pps_pte, &pps_info.pte_count);
+ atomic_sub(pps_unmapped, &pps_info.unmapped_count);
+ atomic_sub(pps_swapped, &pps_info.swapped_count);
}

static void migrate_back_pmd_range(struct mm_struct* mm, pud_t *pud, struct
@@ -2636,17 +2679,13 @@
} while (pgd++, addr = next, addr != end);
}

-LIST_HEAD(pps_head);
-LIST_HEAD(pps_head_buddy);
-
-DEFINE_SPINLOCK(pps_lock);
-
void enter_pps(struct mm_struct* mm, struct vm_area_struct* vma)
{
int condition = VM_READ | VM_WRITE | VM_EXEC | \
VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC | \
VM_GROWSDOWN | VM_GROWSUP | \
- VM_LOCKED | VM_SEQ_READ | VM_RAND_READ | VM_DONTCOPY | VM_ACCOUNT;
+ VM_LOCKED | VM_SEQ_READ | VM_RAND_READ | VM_DONTCOPY | VM_ACCOUNT | \
+ VM_PURE_PRIVATE;
if (!(vma->vm_flags & ~condition) && vma->vm_file == NULL) {
vma->vm_flags |= VM_PURE_PRIVATE;
if (list_empty(&mm->mmlist)) {
Index: linux-2.6.16.29/mm/swapfile.c
===================================================================
--- linux-2.6.16.29.orig/mm/swapfile.c 2007-01-04 14:47:37.000000000 +0800
+++ linux-2.6.16.29/mm/swapfile.c 2007-01-04 14:49:37.000000000 +0800
@@ -544,19 +544,22 @@

static int pps_swapoff(int type)
{
- struct mm_struct* mm;
struct vm_area_struct* vma;
- struct list_head *pos, *lhtemp;
+ struct list_head *pos;
+ struct mm_struct *prev, *mm;
int ret = 0;

+ prev = mm = &init_mm;
+ pos = &init_mm.mmlist;
+ atomic_inc(&prev->mm_users);
spin_lock(&mmlist_lock);
- list_for_each_safe(pos, lhtemp, &init_mm.mmlist) {
+ while ((pos = pos->next) != &init_mm.mmlist) {
mm = list_entry(pos, struct mm_struct, mmlist);
- if (atomic_inc_return(&mm->mm_users) == 1) {
- atomic_dec(&mm->mm_users);
+ if (!atomic_add_unless(&mm->mm_users, 1, 0))
continue;
- }
spin_unlock(&mmlist_lock);
+ mmput(prev);
+ prev = mm;
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
if (!(vma->vm_flags & VM_PURE_PRIVATE))
@@ -568,10 +571,10 @@
break;
}
up_read(&mm->mmap_sem);
- mmput(mm);
spin_lock(&mmlist_lock);
}
spin_unlock(&mmlist_lock);
+ mmput(prev);
return ret;
}

Index: linux-2.6.16.29/mm/vmscan.c
===================================================================
--- linux-2.6.16.29.orig/mm/vmscan.c 2007-01-04 14:47:38.000000000 +0800
+++ linux-2.6.16.29/mm/vmscan.c 2007-01-05 11:42:05.795353536 +0800
@@ -79,6 +79,9 @@
* In this context, it doesn't matter that we scan the
* whole list at once. */
int swap_cluster_max;
+
+ /* pps control command, 0: do stage 1-4, kppsd only; 1: full stages. */
+ int pps_cmd;
};

/*
@@ -1514,6 +1517,17 @@
return ret;
}

+// pps fields.
+static wait_queue_head_t kppsd_wait;
+static struct scan_control wakeup_sc;
+struct pps_info pps_info = {
+ .total = ATOMIC_INIT(0),
+ .pte_count = ATOMIC_INIT(0), // stage 1 and 2.
+ .unmapped_count = ATOMIC_INIT(0), // stage 3 and 4.
+ .swapped_count = ATOMIC_INIT(0) // stage 6.
+};
+// pps end.
+
struct series_t {
pte_t orig_ptes[MAX_SERIES_LENGTH];
pte_t* ptes[MAX_SERIES_LENGTH];
@@ -1564,11 +1578,10 @@
series.series_length = i;
}

-struct delay_tlb_task_t delay_tlb_tasks[32] = { [0 ... 31] = {0} };
+struct delay_tlb_task delay_tlb_tasks[32] = { [0 ... 31] = {0} };

void timer_flush_tlb_tasks(void* data)
{
- // To x86, if we found there were some flushing tasks, we should do
it all together, that is, flush it once.
int i;
#ifdef CONFIG_X86
int flag = 0;
@@ -1591,12 +1604,12 @@
#endif
}

-static struct delay_tlb_task_t* delay_task = NULL;
+static struct delay_tlb_task* delay_task = NULL;
static int vma_index = 0;

-static struct delay_tlb_task_t* search_free_tlb_tasks_slot(void)
+static struct delay_tlb_task* search_free_tlb_tasks_slot(void)
{
- struct delay_tlb_task_t* ret = NULL;
+ struct delay_tlb_task* ret = NULL;
int i;
again:
for (i = 0; i < 32; i++) {
@@ -1650,18 +1663,24 @@

static void end_tlb_tasks(void)
{
- if (!cpus_empty(delay_task->cpu_mask)) {
- atomic_inc(&delay_task->mm->mm_users);
- delay_task->cpu_mask = delay_task->mm->cpu_vm_mask;
- } else
- delay_task->mm = NULL;
+ atomic_inc(&delay_task->mm->mm_users);
+ delay_task->cpu_mask = delay_task->mm->cpu_vm_mask;
delay_task = NULL;
+#ifndef CONFIG_SMP
+ timer_flush_tlb_tasks(NULL);
+#endif
}

static void fill_in_tlb_tasks(struct vm_area_struct* vma, unsigned long addr,
unsigned long end)
{
struct mm_struct* mm;
+ // First, try to combine the task with the previous.
+ if (vma_index != 0 && delay_task->vma[vma_index - 1] == vma &&
+ delay_task->end[vma_index - 1] == addr) {
+ delay_task->end[vma_index - 1] = end;
+ return;
+ }
fill_it:
if (vma_index != 32) {
delay_task->vma[vma_index] = vma;
@@ -1678,11 +1697,11 @@
goto fill_it;
}

-static void shrink_pvma_scan_ptes(struct scan_control* sc,
- struct mm_struct* mm, struct vm_area_struct* vma, pmd_t* pmd,
- unsigned long addr, unsigned long end)
+static void shrink_pvma_scan_ptes(struct scan_control* sc, struct mm_struct*
+ mm, struct vm_area_struct* vma, pmd_t* pmd, unsigned long addr,
+ unsigned long end)
{
- int i;
+ int i, statistic;
spinlock_t* ptl = pte_lockptr(mm, pmd);
pte_t* pte = pte_offset_map(pmd, addr);
int anon_rss = 0;
@@ -1694,6 +1713,8 @@
do {
memset(&series, 0, sizeof(struct series_t));
find_series(&pte, &addr, end);
+ if (sc->pps_cmd == 0 && series.series_stage == 5)
+ continue;
switch (series.series_stage) {
case 1: // PTE -- untouched PTE.
for (i = 0; i < series.series_length; i++) {
@@ -1722,6 +1743,7 @@
* send IPI immediately in fill_in_tlb_tasks.
*/
spin_lock(ptl);
+ statistic = 0;
for (i = 0; i < series.series_length; i++) {
if (unlikely(pte_same(*series.ptes[i], series.orig_ptes[i]))) {
pte_t pte_unmapped = series.orig_ptes[i];
@@ -1734,8 +1756,11 @@
continue;
page_remove_rmap(series.pages[i]);
anon_rss--;
+ statistic++;
}
}
+ atomic_add(statistic, &pps_info.unmapped_count);
+ atomic_sub(statistic, &pps_info.pte_count);
spin_unlock(ptl);
break;
case 3: // Attach SwapPage to PrivatePage.
@@ -1798,15 +1823,17 @@
}
break;
case 5: // UnmappedPTE -- SwappedPTE, reclaim PrivatePage.
+ statistic = 0;
for (i = 0; i < series.series_length; i++) {
struct page* page = series.pages[i];
lock_page(page);
spin_lock(ptl);
- if (unlikely(pte_same(*series.ptes[i], series.orig_ptes[i]))) {
+ if (unlikely(!pte_same(*series.ptes[i], series.orig_ptes[i]))) {
spin_unlock(ptl);
unlock_page(page);
continue;
}
+ statistic++;
swp_entry_t entry = { .val = page_private(page) };
swap_duplicate(entry);
pte_t pte_swp = swp_entry_to_pte(entry);
@@ -1820,6 +1847,9 @@
__pagevec_release_nonlru(&freed_pvec);
sc->nr_reclaimed++;
}
+ atomic_add(statistic, &pps_info.swapped_count);
+ atomic_sub(statistic, &pps_info.unmapped_count);
+ atomic_sub(statistic, &pps_info.total);
break;
case 6:
// NULL operation!
@@ -1831,9 +1861,9 @@
__pagevec_release_nonlru(&freed_pvec);
}

-static void shrink_pvma_pmd_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma, pud_t* pud,
- unsigned long addr, unsigned long end)
+static void shrink_pvma_pmd_range(struct scan_control* sc, struct mm_struct*
+ mm, struct vm_area_struct* vma, pud_t* pud, unsigned long addr,
+ unsigned long end)
{
unsigned long next;
pmd_t* pmd = pmd_offset(pud, addr);
@@ -1845,9 +1875,9 @@
} while (pmd++, addr = next, addr != end);
}

-static void shrink_pvma_pud_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma, pgd_t* pgd,
- unsigned long addr, unsigned long end)
+static void shrink_pvma_pud_range(struct scan_control* sc, struct mm_struct*
+ mm, struct vm_area_struct* vma, pgd_t* pgd, unsigned long addr,
+ unsigned long end)
{
unsigned long next;
pud_t* pud = pud_offset(pgd, addr);
@@ -1859,8 +1889,8 @@
} while (pud++, addr = next, addr != end);
}

-static void shrink_pvma_pgd_range(struct scan_control* sc, struct
mm_struct* mm,
- struct vm_area_struct* vma)
+static void shrink_pvma_pgd_range(struct scan_control* sc, struct mm_struct*
+ mm, struct vm_area_struct* vma)
{
unsigned long next;
unsigned long addr = vma->vm_start;
@@ -1876,18 +1906,21 @@

static void shrink_private_vma(struct scan_control* sc)
{
- struct mm_struct* mm;
struct vm_area_struct* vma;
- struct list_head *pos, *lhtemp;
+ struct list_head *pos;
+ struct mm_struct *prev, *mm;

+ prev = mm = &init_mm;
+ pos = &init_mm.mmlist;
+ atomic_inc(&prev->mm_users);
spin_lock(&mmlist_lock);
- list_for_each_safe(pos, lhtemp, &init_mm.mmlist) {
+ while ((pos = pos->next) != &init_mm.mmlist) {
mm = list_entry(pos, struct mm_struct, mmlist);
- if (atomic_inc_return(&mm->mm_users) == 1) {
- atomic_dec(&mm->mm_users);
+ if (!atomic_add_unless(&mm->mm_users, 1, 0))
continue;
- }
spin_unlock(&mmlist_lock);
+ mmput(prev);
+ prev = mm;
start_tlb_tasks(mm);
if (down_read_trylock(&mm->mmap_sem)) {
for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
@@ -1900,10 +1933,10 @@
up_read(&mm->mmap_sem);
}
end_tlb_tasks();
- mmput(mm);
spin_lock(&mmlist_lock);
}
spin_unlock(&mmlist_lock);
+ mmput(prev);
}

/*
@@ -1949,7 +1982,10 @@
sc.may_swap = 1;
sc.nr_mapped = read_page_state(nr_mapped);

- shrink_private_vma(&sc);
+ wakeup_sc = sc;
+ wakeup_sc.pps_cmd = 1;
+ wake_up_interruptible(&kppsd_wait);
+
inc_page_state(pageoutrun);

for (i = 0; i < pgdat->nr_zones; i++) {
@@ -2086,6 +2122,33 @@
return total_reclaimed;
}

+static int kppsd(void* p)
+{
+ struct task_struct *tsk = current;
+ int timeout;
+ DEFINE_WAIT(wait);
+ daemonize("kppsd");
+ tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE;
+ struct scan_control default_sc;
+ default_sc.gfp_mask = GFP_KERNEL;
+ default_sc.may_writepage = 1;
+ default_sc.may_swap = 1;
+ default_sc.pps_cmd = 0;
+
+ while (1) {
+ try_to_freeze();
+ prepare_to_wait(&kppsd_wait, &wait, TASK_INTERRUPTIBLE);
+ timeout = schedule_timeout(2000);
+ finish_wait(&kppsd_wait, &wait);
+
+ if (timeout)
+ shrink_private_vma(&wakeup_sc);
+ else
+ shrink_private_vma(&default_sc);
+ }
+ return 0;
+}
+
/*
* The background pageout daemon, started as a kernel thread
* from the init process.
@@ -2230,6 +2293,15 @@
}
#endif /* CONFIG_HOTPLUG_CPU */

+static int __init kppsd_init(void)
+{
+ init_waitqueue_head(&kppsd_wait);
+ kernel_thread(kppsd, NULL, CLONE_KERNEL);
+ return 0;
+}
+
+module_init(kppsd_init)
+
static int __init kswapd_init(void)
{
pg_data_t *pgdat;

2007-01-05 23:11:38

Sorry, I can't be online regularly, that is, can't synchronize Linux CVS, so
only work on a fixed kernel version. Documentation/vm_pps.txt isn't only a patch
overview but also a changelog.

>
> Great!
>
> Do you have patch against 2.6.19?
>
>
> Thanks!
>
> --
> Al
>
>