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Message-ID: <ad15739f-db2a-3b2a-1097-d80feadcfd40@linux.ibm.com>
Date: Tue, 7 Jan 2020 11:30:58 +0100
From: Zaslonko Mikhail <zaslonko@...ux.ibm.com>
To: Josef Bacik <josef@...icpanda.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Chris Mason <clm@...com>, David Sterba <dsterba@...e.com>
Cc: Richard Purdie <rpurdie@...ys.net>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Eduard Shishkin <edward6@...ux.ibm.com>,
Ilya Leoshkevich <iii@...ux.ibm.com>,
linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/6] btrfs: Use larger zlib buffer for s390 hardware
compression
Hello,
On 06.01.2020 17:40, Josef Bacik wrote:
> On 1/3/20 5:33 PM, Mikhail Zaslonko wrote:
>> 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.
>>
>> Signed-off-by: Mikhail Zaslonko <zaslonko@...ux.ibm.com>
>> ---
>> fs/btrfs/compression.c | 2 +-
>> fs/btrfs/zlib.c | 128 ++++++++++++++++++++++++++++++-----------
>> 2 files changed, 94 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..159486801631 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;
>> };
>> @@ -61,7 +64,17 @@ 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;
>> @@ -78,6 +91,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
>> unsigned long *total_in, unsigned long *total_out)
>> {
>> struct workspace *workspace = list_entry(ws, struct workspace, list);
>> + int i;
>> int ret;
>> char *data_in;
>> char *cpage_out;
>> @@ -85,6 +99,7 @@ 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 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;
>> @@ -102,9 +117,6 @@ 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 +126,48 @@ 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) {
>> + 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;
>> + }
>
> Is there a reason to leave the last in_page mapped here? I realize we'll clean it up further down, but since we're copying everything into the buf anyway why not just map->copy->unmap for everything?
The idea was not to copy the last data chunk if it fits in a single page, thus using the same code flow as for a PAGE_SIZE buffer (the ELSE branch below).
>
>> + 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,
>> + workspace->buf_size);
>> + }
>> +
>> ret = zlib_deflate(&workspace->strm, Z_SYNC_FLUSH);
>> if (ret != Z_OK) {
>> pr_debug("BTRFS: deflate in loop returned %d\n",
>> @@ -136,6 +184,7 @@ int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
>> ret = -E2BIG;
>> goto out;
>> }
>> +
>
> Extra newline. Thanks,
>
> Josef
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