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Subject[PATCH v4] btrfs: Use larger zlib buffer for s390 hardware compression
Date
In order to benefit from s390 zlib hardware compression support,
increase the btrfs zlib workspace buffer size from 1 to 4 pages (if
s390 zlib hardware support is enabled on the machine). This brings up
to 60% better performance in hardware on s390 compared to the PAGE_SIZE
buffer and much more compared to the software zlib processing in btrfs.
In case of memory pressure, fall back to a single page buffer during
workspace allocation.
The data compressed with larger input buffers will still conform to zlib
standard and thus can be decompressed also on a systems that uses only
PAGE_SIZE buffer for btrfs zlib.

Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
---
fs/btrfs/compression.c | 2 +-
fs/btrfs/zlib.c | 135 ++++++++++++++++++++++++++++++-----------
2 files changed, 101 insertions(+), 36 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index ee834ef7beb4..6bd0e75a822c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1285,7 +1285,7 @@ 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 a6c90a003c12..05615a1099db 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -20,9 +20,13 @@
#include <linux/refcount.h>
#include "compression.h"

+/* workspace buffer size for s390 zlib hardware support */
+#define ZLIB_DFLTCC_BUF_SIZE (4 * PAGE_SIZE)
+
struct workspace {
z_stream strm;
char *buf;
+ unsigned int buf_size;
struct list_head list;
int level;
};
@@ -61,7 +65,21 @@ 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;
+ /*
+ * In case of s390 zlib hardware support, allocate lager workspace
+ * buffer. If allocator fails, fall back to a single page buffer.
+ */
+ 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;

@@ -85,6 +103,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
struct page *in_page = NULL;
struct page *out_page = NULL;
unsigned long bytes_left;
+ unsigned int 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;
@@ -102,9 +121,6 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
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;
@@ -114,12 +130,51 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
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 input pages and copy the contents to
+ * the workspace buffer if required.
+ */
+ 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);
+ if (in_buf_pages > 1) {
+ int i;
+
+ for (i = 0; i < in_buf_pages; i++) {
+ if (in_page) {
+ kunmap(in_page);
+ put_page(in_page);
+ }
+ in_page = find_get_page(mapping,
+ start >> PAGE_SHIFT);
+ data_in = kmap(in_page);
+ memcpy(workspace->buf + i * PAGE_SIZE,
+ data_in, PAGE_SIZE);
+ start += PAGE_SIZE;
+ }
+ workspace->strm.next_in = workspace->buf;
+ } else {
+ if (in_page) {
+ kunmap(in_page);
+ put_page(in_page);
+ }
+ in_page = find_get_page(mapping,
+ start >> PAGE_SHIFT);
+ data_in = kmap(in_page);
+ start += PAGE_SIZE;
+ workspace->strm.next_in = data_in;
+ }
+ workspace->strm.avail_in = min(bytes_left,
+ (unsigned long) workspace->buf_size);
+ }
+
ret = zlib_deflate(&workspace->strm, Z_SYNC_FLUSH);
if (ret != Z_OK) {
pr_debug("BTRFS: deflate in loop returned %d\n",
@@ -161,33 +216,43 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
/* 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;
@@ -231,7 +296,7 @@ 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. */
@@ -270,7 +335,7 @@ 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;
@@ -320,7 +385,7 @@ 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. */
@@ -364,7 +429,7 @@ 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);
@@ -375,7 +440,7 @@ 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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