Hello, Could you please review the patch for btrfs below. Apart from falling back to 1 page, I have set the condition to allocate 4-pages zlib workspace buffer only if s390 Deflate-Conversion facility is installed and enabled. Thus, it will take effect on s390 architecture only. Currently in zlib_compress_pages() I always copy input pages to the workspace buffer prior to zlib_deflate call. Would that make sense, to pass the page itself, as before, based on the workspace buf_size (for 1-page buffer)? As for calling zlib_deflate with Z_FINISH flush parameter in a loop until Z_STREAM_END is returned, that comes in agreement with the zlib manual. Please see for more details: https://lkml.org/lkml/2019/12/9/537 Thanks, Mikhail On 09.12.2019 16:29, Mikhail Zaslonko wrote: > 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@xxxxxxxxxxxxx> > --- > 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) >
