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Subject[PATCH v2 6/6] btrfs: Use larger zlib buffer for s390 hardware compression
Date
Due to the small size of zlib buffer (1 page) set in btrfs code, s390
hardware compression is rather limited in terms of performance. Increasing
the buffer size to 4 pages when s390 zlib hardware support is enabled
would bring significant benefit to btrfs zlib (up to 60% better performance
compared to the PAGE_SIZE buffer). In case of memory pressure we fall back
to a single page buffer during workspace allocation.

Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
---
fs/btrfs/compression.c | 2 +-
fs/btrfs/zlib.c | 118 +++++++++++++++++++++++++++--------------
2 files changed, 80 insertions(+), 40 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index b05b361e2062..f789b356fd8b 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1158,7 +1158,7 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
/* copy bytes from the working buffer into the pages */
while (working_bytes > 0) {
bytes = min_t(unsigned long, bvec.bv_len,
- PAGE_SIZE - buf_offset);
+ PAGE_SIZE - (buf_offset % PAGE_SIZE));
bytes = min(bytes, working_bytes);

kaddr = kmap_atomic(bvec.bv_page);
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index df1aace5df50..0bc0d57ba233 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -20,9 +20,12 @@
#include <linux/refcount.h>
#include "compression.h"

+#define ZLIB_DFLTCC_BUF_SIZE (4 * PAGE_SIZE)
+
struct workspace {
z_stream strm;
char *buf;
+ unsigned long buf_size;
struct list_head list;
int level;
};
@@ -76,7 +79,17 @@ static struct list_head *zlib_alloc_workspace(unsigned int level)
zlib_inflate_workspacesize());
workspace->strm.workspace = kvmalloc(workspacesize, GFP_KERNEL);
workspace->level = level;
- workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ workspace->buf = NULL;
+ if (zlib_deflate_dfltcc_enabled()) {
+ workspace->buf = kmalloc(ZLIB_DFLTCC_BUF_SIZE,
+ __GFP_NOMEMALLOC | __GFP_NORETRY |
+ __GFP_NOWARN | GFP_NOIO);
+ workspace->buf_size = ZLIB_DFLTCC_BUF_SIZE;
+ }
+ if (!workspace->buf) {
+ workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ workspace->buf_size = PAGE_SIZE;
+ }
if (!workspace->strm.workspace || !workspace->buf)
goto fail;

@@ -97,6 +110,7 @@ static int zlib_compress_pages(struct list_head *ws,
unsigned long *total_out)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
+ int i;
int ret;
char *data_in;
char *cpage_out;
@@ -104,6 +118,7 @@ static int zlib_compress_pages(struct list_head *ws,
struct page *in_page = NULL;
struct page *out_page = NULL;
unsigned long bytes_left;
+ unsigned long in_buf_pages;
unsigned long len = *total_out;
unsigned long nr_dest_pages = *out_pages;
const unsigned long max_out = nr_dest_pages * PAGE_SIZE;
@@ -121,9 +136,6 @@ static int zlib_compress_pages(struct list_head *ws,
workspace->strm.total_in = 0;
workspace->strm.total_out = 0;

- in_page = find_get_page(mapping, start >> PAGE_SHIFT);
- data_in = kmap(in_page);
-
out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (out_page == NULL) {
ret = -ENOMEM;
@@ -133,12 +145,34 @@ static int zlib_compress_pages(struct list_head *ws,
pages[0] = out_page;
nr_pages = 1;

- workspace->strm.next_in = data_in;
+ workspace->strm.next_in = workspace->buf;
+ workspace->strm.avail_in = 0;
workspace->strm.next_out = cpage_out;
workspace->strm.avail_out = PAGE_SIZE;
- workspace->strm.avail_in = min(len, PAGE_SIZE);

while (workspace->strm.total_in < len) {
+ /* get next set of pages and copy their contents to
+ * the input buffer for the following deflate call
+ */
+ if (workspace->strm.avail_in == 0) {
+ bytes_left = len - workspace->strm.total_in;
+ in_buf_pages = min(DIV_ROUND_UP(bytes_left, PAGE_SIZE),
+ workspace->buf_size / PAGE_SIZE);
+ for (i = 0; i < in_buf_pages; i++) {
+ in_page = find_get_page(mapping,
+ start >> PAGE_SHIFT);
+ data_in = kmap(in_page);
+ memcpy(workspace->buf + i*PAGE_SIZE, data_in,
+ PAGE_SIZE);
+ kunmap(in_page);
+ put_page(in_page);
+ start += PAGE_SIZE;
+ }
+ workspace->strm.avail_in = min(bytes_left,
+ workspace->buf_size);
+ workspace->strm.next_in = workspace->buf;
+ }
+
ret = zlib_deflate(&workspace->strm, Z_SYNC_FLUSH);
if (ret != Z_OK) {
pr_debug("BTRFS: deflate in loop returned %d\n",
@@ -155,6 +189,7 @@ static int zlib_compress_pages(struct list_head *ws,
ret = -E2BIG;
goto out;
}
+
/* we need another page for writing out. Test this
* before the total_in so we will pull in a new page for
* the stream end if required
@@ -180,33 +215,42 @@ static int zlib_compress_pages(struct list_head *ws,
/* we're all done */
if (workspace->strm.total_in >= len)
break;
-
- /* we've read in a full page, get a new one */
- if (workspace->strm.avail_in == 0) {
- if (workspace->strm.total_out > max_out)
- break;
-
- bytes_left = len - workspace->strm.total_in;
- kunmap(in_page);
- put_page(in_page);
-
- start += PAGE_SIZE;
- in_page = find_get_page(mapping,
- start >> PAGE_SHIFT);
- data_in = kmap(in_page);
- workspace->strm.avail_in = min(bytes_left,
- PAGE_SIZE);
- workspace->strm.next_in = data_in;
- }
+ if (workspace->strm.total_out > max_out)
+ break;
}
workspace->strm.avail_in = 0;
- ret = zlib_deflate(&workspace->strm, Z_FINISH);
- zlib_deflateEnd(&workspace->strm);
-
- if (ret != Z_STREAM_END) {
- ret = -EIO;
- goto out;
+ /* call deflate with Z_FINISH flush parameter providing more output
+ * space but no more input data, until it returns with Z_STREAM_END
+ */
+ while (ret != Z_STREAM_END) {
+ ret = zlib_deflate(&workspace->strm, Z_FINISH);
+ if (ret == Z_STREAM_END)
+ break;
+ if (ret != Z_OK && ret != Z_BUF_ERROR) {
+ zlib_deflateEnd(&workspace->strm);
+ ret = -EIO;
+ goto out;
+ } else if (workspace->strm.avail_out == 0) {
+ /* get another page for the stream end */
+ kunmap(out_page);
+ if (nr_pages == nr_dest_pages) {
+ out_page = NULL;
+ ret = -E2BIG;
+ goto out;
+ }
+ out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+ if (out_page == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ cpage_out = kmap(out_page);
+ pages[nr_pages] = out_page;
+ nr_pages++;
+ workspace->strm.avail_out = PAGE_SIZE;
+ workspace->strm.next_out = cpage_out;
+ }
}
+ zlib_deflateEnd(&workspace->strm);

if (workspace->strm.total_out >= workspace->strm.total_in) {
ret = -E2BIG;
@@ -221,10 +265,6 @@ static int zlib_compress_pages(struct list_head *ws,
if (out_page)
kunmap(out_page);

- if (in_page) {
- kunmap(in_page);
- put_page(in_page);
- }
return ret;
}

@@ -250,7 +290,7 @@ static int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)

workspace->strm.total_out = 0;
workspace->strm.next_out = workspace->buf;
- workspace->strm.avail_out = PAGE_SIZE;
+ workspace->strm.avail_out = workspace->buf_size;

/* If it's deflate, and it's got no preset dictionary, then
we can tell zlib to skip the adler32 check. */
@@ -289,7 +329,7 @@ static int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
}

workspace->strm.next_out = workspace->buf;
- workspace->strm.avail_out = PAGE_SIZE;
+ workspace->strm.avail_out = workspace->buf_size;

if (workspace->strm.avail_in == 0) {
unsigned long tmp;
@@ -340,7 +380,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
workspace->strm.total_in = 0;

workspace->strm.next_out = workspace->buf;
- workspace->strm.avail_out = PAGE_SIZE;
+ workspace->strm.avail_out = workspace->buf_size;
workspace->strm.total_out = 0;
/* If it's deflate, and it's got no preset dictionary, then
we can tell zlib to skip the adler32 check. */
@@ -384,7 +424,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
buf_offset = 0;

bytes = min(PAGE_SIZE - pg_offset,
- PAGE_SIZE - buf_offset);
+ PAGE_SIZE - (buf_offset % PAGE_SIZE));
bytes = min(bytes, bytes_left);

kaddr = kmap_atomic(dest_page);
@@ -395,7 +435,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
bytes_left -= bytes;
next:
workspace->strm.next_out = workspace->buf;
- workspace->strm.avail_out = PAGE_SIZE;
+ workspace->strm.avail_out = workspace->buf_size;
}

if (ret != Z_STREAM_END && bytes_left != 0)
--
2.17.1
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