[RFC PATCH 12/21] Use linked lists instead of arrays for relaybuffers.
From: Tom Zanussi
Date: Thu Oct 16 2008 - 02:16:25 EST
---
include/linux/relay.h | 12 ++++-
kernel/relay.c | 108 ++++++++++++++++++++++++------------------------
2 files changed, 63 insertions(+), 57 deletions(-)
diff --git a/include/linux/relay.h b/include/linux/relay.h
index 35a6e8c..35912d6 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -30,14 +30,21 @@
#define RCHAN_MODE_OVERWRITE 0x00000001 /* 'flight' mode */
#define RCHAN_GLOBAL_BUFFER 0x00000002 /* not using per-cpu */
+struct relay_page
+{
+ struct page *page;
+ struct list_head list;
+};
+
/*
* Per-cpu relay channel buffer
*/
struct rchan_buf
{
void *data; /* address of current page */
- struct page *page; /* current page */
+ struct relay_page *page; /* current write page */
size_t offset; /* current offset into page */
+ size_t consumed_offset; /* bytes consumed in cur page */
size_t produced; /* count of pages produced */
size_t consumed; /* count of pages consumed */
struct rchan *chan; /* associated channel */
@@ -45,10 +52,9 @@ struct rchan_buf
struct timer_list timer; /* reader wake-up timer */
struct dentry *dentry; /* channel file dentry */
struct kref kref; /* channel buffer refcount */
- struct page **page_array; /* array of current buffer pages */
+ struct list_head pages; /* current set of unconsumed pages */
unsigned int page_count; /* number of current buffer pages */
unsigned int finalized; /* buffer has been finalized */
- size_t consumed_offset; /* bytes consumed in cur page */
size_t early_bytes; /* bytes consumed before VFS inited */
unsigned int cpu; /* this buf's cpu */
} ____cacheline_aligned;
diff --git a/kernel/relay.c b/kernel/relay.c
index 1a151b8..198301d 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -36,19 +36,35 @@ static void relay_file_mmap_close(struct vm_area_struct *vma)
buf->chan->cb->buf_unmapped(buf, vma->vm_file);
}
+/* yeah, stupid, but temporary */
+static struct relay_page *find_buf_page_n(struct rchan_buf *buf, int n)
+{
+ struct list_head *page = buf->pages.next;
+ struct relay_page *rpage;
+
+ while(n--)
+ page = page->next;
+
+ rpage = list_entry(page, struct relay_page, list);
+
+ return rpage;
+}
+
/*
* fault() vm_op implementation for relay file mapping.
*/
static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct page *page;
+ struct relay_page *rpage;
struct rchan_buf *buf = vma->vm_private_data;
pgoff_t pgoff = vmf->pgoff;
if (!buf)
return VM_FAULT_OOM;
- page = buf->page_array[pgoff];
+ rpage = find_buf_page_n(buf, pgoff);
+ page = rpage->page;
if (!page)
return VM_FAULT_SIGBUS;
@@ -66,35 +82,6 @@ static struct vm_operations_struct relay_file_mmap_ops = {
.close = relay_file_mmap_close,
};
-/*
- * allocate an array of pointers of struct page
- */
-static struct page **relay_alloc_page_array(unsigned int n_pages)
-{
- struct page **array;
- size_t pa_size = n_pages * sizeof(struct page *);
-
- if (pa_size > PAGE_SIZE) {
- array = vmalloc(pa_size);
- if (array)
- memset(array, 0, pa_size);
- } else {
- array = kzalloc(pa_size, GFP_KERNEL);
- }
- return array;
-}
-
-/*
- * free an array of pointers of struct page
- */
-static void relay_free_page_array(struct page **array)
-{
- if (is_vmalloc_addr(array))
- vfree(array);
- else
- kfree(array);
-}
-
/**
* relay_mmap_buf: - mmap channel buffer to process address space
* @buf: relay channel buffer
@@ -131,27 +118,29 @@ static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
*/
static int relay_alloc_buf(struct rchan_buf *buf)
{
- unsigned int i, j;
-
- buf->page_array = relay_alloc_page_array(buf->chan->n_pages + 1);
- if (!buf->page_array)
- return -ENOMEM;
+ unsigned int i;
+ struct relay_page *rpage = NULL;
for (i = 0; i < buf->chan->n_pages; i++) {
- buf->page_array[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
- if (unlikely(!buf->page_array[i]))
+ rpage = kmalloc(sizeof(struct relay_page), GFP_KERNEL);
+ if (unlikely(!rpage))
+ goto depopulate;
+ rpage->page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (unlikely(!rpage->page))
goto depopulate;
- set_page_private(buf->page_array[i], (unsigned long)buf);
+ set_page_private(rpage->page, (unsigned long)buf);
+ list_add_tail(&rpage->list, &buf->pages);
}
- buf->page_array[buf->chan->n_pages] = buf->page_array[0];
buf->page_count = buf->chan->n_pages;
return 0;
depopulate:
- for (j = 0; j < i; j++)
- __free_page(buf->page_array[j]);
- relay_free_page_array(buf->page_array);
+ list_for_each_entry(rpage, &buf->pages, list) {
+ __free_page(rpage->page);
+ list_del(&rpage->list);
+ }
+
return -ENOMEM;
}
@@ -167,6 +156,7 @@ static struct rchan_buf *relay_create_buf(struct rchan *chan)
if (!buf)
return NULL;
+ INIT_LIST_HEAD(&buf->pages);
buf->chan = chan;
kref_get(&buf->chan->kref);
@@ -199,11 +189,13 @@ static void relay_destroy_channel(struct kref *kref)
static void relay_destroy_buf(struct rchan_buf *buf)
{
struct rchan *chan = buf->chan;
- unsigned int i;
+ struct relay_page *rpage, *rpage2;
- for (i = 0; i < buf->page_count; i++)
- __free_page(buf->page_array[i]);
- relay_free_page_array(buf->page_array);
+ list_for_each_entry_safe(rpage, rpage2, &buf->pages, list) {
+ __free_page(rpage->page);
+ list_del(&rpage->list);
+ kfree(rpage);
+ }
chan->buf[buf->cpu] = NULL;
kfree(buf);
@@ -344,8 +336,8 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
buf->consumed = 0;
buf->consumed_offset = 0;
buf->finalized = 0;
- buf->page = buf->page_array[0];
- buf->data = page_address(buf->page);
+ buf->page = list_first_entry(&buf->pages, struct relay_page, list);
+ buf->data = page_address(buf->page->page);
buf->offset = 0;
buf->chan->cb->new_page(buf, buf->data);
@@ -719,6 +711,7 @@ size_t relay_switch_page_default_callback(struct rchan_buf *buf,
void **reserved)
{
size_t remainder;
+ struct list_head *next_page;
if (unlikely(relay_event_toobig(buf, length)))
goto toobig;
@@ -735,8 +728,11 @@ size_t relay_switch_page_default_callback(struct rchan_buf *buf,
relay_inc_produced(buf);
relay_update_filesize(buf, PAGE_SIZE + remainder);
- buf->page = buf->page_array[buf->produced % buf->chan->n_pages];
- buf->data = page_address(buf->page);
+ next_page = buf->page->list.next;
+ if (next_page == &buf->pages)
+ next_page = buf->pages.next;
+ buf->page = list_entry(next_page, struct relay_page, list);
+ buf->data = page_address(buf->page->page);
buf->offset = 0; /* remainder will be added by caller */
buf->chan->cb->new_page(buf, buf->data);
@@ -943,12 +939,12 @@ static size_t relay_file_read_page_avail(size_t read_pos,
struct rchan_buf *buf)
{
size_t avail;
- struct page *read_page, *write_page;
+ struct relay_page *read_page, *write_page;
size_t read_offset, write_offset;
write_page = buf->page;
write_offset = buf->offset;
- read_page = buf->page_array[read_pos / PAGE_SIZE];
+ read_page = find_buf_page_n(buf, read_pos / PAGE_SIZE);
read_offset = read_pos % PAGE_SIZE;
if (read_page == write_page && read_offset == write_offset)
@@ -1010,8 +1006,10 @@ static int page_read_actor(size_t read_start,
{
void *from;
int ret = 0;
+ struct relay_page *rpage;
- from = page_address(buf->page_array[read_start / PAGE_SIZE]);
+ rpage = find_buf_page_n(buf, read_start / PAGE_SIZE);
+ from = page_address(rpage->page);
from += read_start % PAGE_SIZE;
ret = avail;
if (copy_to_user(desc->arg.buf, from, avail)) {
@@ -1149,13 +1147,15 @@ static int page_splice_actor(struct file *in,
for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
unsigned int this_len;
+ struct relay_page *rpage;
if (!len)
break;
this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
- spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
+ rpage = find_buf_page_n(rbuf, pidx);
+ spd.pages[spd.nr_pages] = rpage->page;
spd.partial[spd.nr_pages].offset = poff;
spd.partial[spd.nr_pages].len = this_len;
--
1.5.3.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/