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btrfs: send: lower memory requirements in common case 

The fs_path structure uses an inline buffer and falls back to a chain of
allocations, but vmalloc is not necessary because PATH_MAX fits into
PAGE_SIZE.

The size of fs_path has been reduced to 256 bytes from PAGE_SIZE,
usually 4k. Experimental measurements show that most paths on a single
filesystem do not exceed 200 bytes, and these get stored into the inline
buffer directly, which is now 230 bytes. Longer paths are kmalloced when
needed.

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
David Sterba 2014-02-05 16:17:34 +01:00 committed by Josef Bacik
parent dff6d0adbe
commit ace0105076
1 changed files with 37 additions and 69 deletions
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106
fs/btrfs/send.c
View File

@ -57,7 +57,12 @@ struct fs_path {
unsigned short reversed:1;
char inline_buf[];
};
char pad[PAGE_SIZE];
/*
* Average path length does not exceed 200 bytes, we'll have
* better packing in the slab and higher chance to satisfy
* a allocation later during send.
*/
char pad[256];
};
};
#define FS_PATH_INLINE_SIZE \
@ -262,12 +267,8 @@ static void fs_path_free(struct fs_path *p)
{
if (!p)
return;
if (p->buf != p->inline_buf) {
if (is_vmalloc_addr(p->buf))
vfree(p->buf);
else
kfree(p->buf);
}
if (p->buf != p->inline_buf)
kfree(p->buf);
kfree(p);
}
@ -287,40 +288,31 @@ static int fs_path_ensure_buf(struct fs_path *p, int len)
if (p->buf_len >= len)
return 0;
/*
* First time the inline_buf does not suffice
*/
if (p->buf == p->inline_buf) {
p->buf = kmalloc(len, GFP_NOFS);
if (!p->buf)
return -ENOMEM;
/*
* The real size of the buffer is bigger, this will let the
* fast path happen most of the time
*/
p->buf_len = ksize(p->buf);
} else {
char *tmp;
tmp = krealloc(p->buf, len, GFP_NOFS);
if (!tmp)
return -ENOMEM;
p->buf = tmp;
p->buf_len = ksize(p->buf);
}
path_len = p->end - p->start;
old_buf_len = p->buf_len;
len = PAGE_ALIGN(len);
if (p->buf == p->inline_buf) {
tmp_buf = kmalloc(len, GFP_NOFS | __GFP_NOWARN);
if (!tmp_buf) {
tmp_buf = vmalloc(len);
if (!tmp_buf)
return -ENOMEM;
}
memcpy(tmp_buf, p->buf, p->buf_len);
p->buf = tmp_buf;
p->buf_len = len;
} else {
if (is_vmalloc_addr(p->buf)) {
tmp_buf = vmalloc(len);
if (!tmp_buf)
return -ENOMEM;
memcpy(tmp_buf, p->buf, p->buf_len);
vfree(p->buf);
} else {
tmp_buf = krealloc(p->buf, len, GFP_NOFS);
if (!tmp_buf) {
tmp_buf = vmalloc(len);
if (!tmp_buf)
return -ENOMEM;
memcpy(tmp_buf, p->buf, p->buf_len);
kfree(p->buf);
}
}
p->buf = tmp_buf;
p->buf_len = len;
}
if (p->reversed) {
tmp_buf = p->buf + old_buf_len - path_len - 1;
p->end = p->buf + p->buf_len - 1;
@ -911,9 +903,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
struct btrfs_dir_item *di;
struct btrfs_key di_key;
char *buf = NULL;
char *buf2 = NULL;
int buf_len;
int buf_virtual = 0;
const int buf_len = PATH_MAX;
u32 name_len;
u32 data_len;
u32 cur;
@ -923,7 +913,6 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
int num;
u8 type;
buf_len = PAGE_SIZE;
buf = kmalloc(buf_len, GFP_NOFS);
if (!buf) {
ret = -ENOMEM;
@ -945,30 +934,12 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
type = btrfs_dir_type(eb, di);
btrfs_dir_item_key_to_cpu(eb, di, &di_key);
/*
* Path too long
*/
if (name_len + data_len > buf_len) {
buf_len = PAGE_ALIGN(name_len + data_len);
if (buf_virtual) {
buf2 = vmalloc(buf_len);
if (!buf2) {
ret = -ENOMEM;
goto out;
}
vfree(buf);
} else {
buf2 = krealloc(buf, buf_len, GFP_NOFS);
if (!buf2) {
buf2 = vmalloc(buf_len);
if (!buf2) {
ret = -ENOMEM;
goto out;
}
kfree(buf);
buf_virtual = 1;
}
}
buf = buf2;
buf2 = NULL;
ret = -ENAMETOOLONG;
goto out;
}
read_extent_buffer(eb, buf, (unsigned long)(di + 1),
@ -991,10 +962,7 @@ static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
}
out:
if (buf_virtual)
vfree(buf);
else
kfree(buf);
kfree(buf);
return ret;
}