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Subject[PATCH 5/6] mm: Support address range reclaim
Date
This patch adds address range reclaim of a process.
The requirement is following as,

Like webkit1, it uses a address space for handling multi tabs.
IOW, it uses *one* process model so all tabs shares address space
of the process. In such scenario, per-process reclaim is rather
coarse-grained so this patch supports more fine-grained reclaim
for being able to reclaim target address range of the process.
For reclaim target range, you should use following format.

echo 4 [address] [size] > /proc/pid/reclaim

So reclaim konb's interface is following as.

echo 1 > /proc/pid/reclaim
reclaim file-backed pages only

echo 2 > /proc/pid/reclaim
reclaim anonymous pages only

echo 3 > /proc/pid/reclaim
reclaim all pages

echo 4 $((1<<20)) 4096 > /proc/pid/reclaim
reclaim file-backed pages in (0x100000 - 0x101000)
echo 5 $((1<<20)) 4096 > /proc/pid/reclaim
reclaim anonymous pages in (0x100000 - 0x101000)
echo 6 $((1<<20)) 4096 > /proc/pid/reclaim
reclaim all pages in (0x100000 - 0x101000)

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
fs/proc/task_mmu.c | 123 ++++++++++++++++++++++++++++++++++++++++-------------
mm/internal.h | 3 ++
2 files changed, 96 insertions(+), 30 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3f67b32..5bd00d9 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1228,67 +1228,130 @@ cont:
return 0;
}

-#define RECLAIM_FILE (1 << 0)
-#define RECLAIM_ANON (1 << 1)
-#define RECLAIM_ALL (RECLAIM_FILE | RECLAIM_ANON)
+enum reclaim_type {
+ RECLAIM_FILE = 1,
+ RECLAIM_ANON,
+ RECLAIM_ALL,
+ RECLAIM_FILE_RANGE,
+ RECLAIM_ANON_RANGE,
+ RECLAIM_BOTH_RANGE,
+};

static ssize_t reclaim_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct task_struct *task;
- char buffer[PROC_NUMBUF];
+ char buffer[200];
struct mm_struct *mm;
struct vm_area_struct *vma;
int type;
- int rv;
+ int ret;
+ char *sptr, *token;
+ unsigned long len_in;
+ unsigned long start = 0;
+ unsigned long end = 0;
+ struct mm_walk reclaim_walk = {};

memset(buffer, 0, sizeof(buffer));
if (count > sizeof(buffer) - 1)
- count = sizeof(buffer) - 1;
+ goto out_err;
+
if (copy_from_user(buffer, buf, count))
return -EFAULT;
- rv = kstrtoint(strstrip(buffer), 10, &type);
- if (rv < 0)
- return rv;
- if (type < RECLAIM_FILE || type > RECLAIM_ALL)
- return -EINVAL;
+
+ sptr = strstrip(buffer);
+ token = strsep(&sptr, " ");
+ if (!token)
+ goto out_err;
+ ret = kstrtoint(token, 10, &type);
+ if (ret < 0 || (type < RECLAIM_FILE || type > RECLAIM_BOTH_RANGE))
+ goto out_err;
+
+ if (type > RECLAIM_ALL) {
+ size_t len;
+ token = strsep(&sptr, " ");
+ if (!token)
+ goto out_err;
+ ret = kstrtoul(token, 10, &start);
+ if (ret < 0)
+ goto out_err;
+
+ token = strsep(&sptr, " ");
+ if (!token)
+ goto out_err;
+ ret = kstrtoul(token, 10, &len_in);
+ if (ret < 0)
+ goto out_err;
+ len = (len_in + ~PAGE_MASK) & PAGE_MASK;
+
+ /*
+ * Check to see whether len was rounded up from small -ve
+ * to zero.
+ */
+ if (len_in && !len)
+ goto out_err;
+
+ end = start + len;
+ if (end < start)
+ goto out_err;
+ }
+
task = get_proc_task(file->f_path.dentry->d_inode);
if (!task)
return -ESRCH;
+
mm = get_task_mm(task);
- if (mm) {
- struct mm_walk reclaim_walk = {
- .pmd_entry = reclaim_pte_range,
- .mm = mm,
- };
- down_read(&mm->mmap_sem);
+ if (!mm)
+ goto out;
+
+ reclaim_walk.mm = mm;
+ reclaim_walk.pmd_entry = reclaim_pte_range;
+
+ down_read(&mm->mmap_sem);
+ if (type > RECLAIM_ALL) {
+ vma = find_vma(mm, start);
+ while (vma) {
+ if (vma->vm_start > end)
+ break;
+
+ reclaim_walk.private = vma;
+ if (is_vm_hugetlb_page(vma))
+ continue;
+ if (type == RECLAIM_ANON_RANGE && vma->vm_file)
+ continue;
+ if (type == RECLAIM_FILE_RANGE && !vma->vm_file)
+ continue;
+
+ walk_page_range(max(vma->vm_start, start),
+ min(vma->vm_end, end),
+ &reclaim_walk);
+
+ vma = vma->vm_next;
+ }
+ } else {
for (vma = mm->mmap; vma; vma = vma->vm_next) {
reclaim_walk.private = vma;
if (is_vm_hugetlb_page(vma))
continue;
- /*
- * Writing 1 to /proc/pid/reclaim only affects file
- * mapped pages.
- *
- * Writing 2 to /proc/pid/reclaim enly affects
- * anonymous pages.
- *
- * Writing 3 to /proc/pid/reclaim affects all pages.
- */
if (type == RECLAIM_ANON && vma->vm_file)
continue;
if (type == RECLAIM_FILE && !vma->vm_file)
continue;
walk_page_range(vma->vm_start, vma->vm_end,
- &reclaim_walk);
+ &reclaim_walk);
}
- flush_tlb_mm(mm);
- up_read(&mm->mmap_sem);
- mmput(mm);
}
+
+ flush_tlb_mm(mm);
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+out:
put_task_struct(task);

return count;
+
+out_err:
+ return -EINVAL;
}

const struct file_operations proc_reclaim_operations = {
diff --git a/mm/internal.h b/mm/internal.h
index 589a29b..1f7ce8f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -85,6 +85,9 @@ static inline void get_page_foll(struct page *page)

extern unsigned long highest_memmap_pfn;

+extern int isolate_lru_page(struct page *page);
+extern void putback_lru_page(struct page *page);
+
/*
* in mm/rmap.c:
*/
--
1.8.2


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