On Sat, Jul 01, 2017 at 07:56:02PM +0300, Timofey Titovets wrote:
> Add a heuristic computation before compression,
> for avoiding load resource heavy compression workspace,
> if data are probably can't be compressed
>
> Signed-off-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
> --- /dev/null
> +++ b/fs/btrfs/heuristic.c
For the new heuristic-related code, please use the compression.h and .c
files and don't add a new one. When we're going to add the clever
heuristics, that could go to a separate file.
> @@ -0,0 +1,336 @@
> +enum compression_advice btrfs_compress_heuristic(struct inode *inode,
This returns enum but the caller treats it as a bool, this should be
synced up.
> + u64 start, u64 end)
> +{
> + enum compression_advice ret = COMPRESS_COST_UNKNOWN;
> + u64 input_size = end - start;
> + u64 index = start >> PAGE_SHIFT;
> + u64 end_index = end >> PAGE_SHIFT;
> + struct page *page;
> + u32 a, b, c;
> + u32 offset_count, shift, sample_size;
> + u8 *sample;
> + u8 *input_data;
> +
> + /*
> + * In data: 128K 64K 32K 4K
> + * Sample: 4096b 3072b 2048b 1024b
> + * Avoid allocating array bigger then 4kb
> + */
> + if (input_size >= 96*1024)
> + offset_count = 256;
> + else
> + offset_count = 64 + input_size/512;
> +
> + shift = input_size/offset_count;
> + sample_size = offset_count*READ_SIZE;
> +
> + /*
> + * speedup by copy data to sample array +30%
> + * I think it's because of memcpy optimizations and
> + * cpu cache hits
> + */
> + sample = kmalloc(sample_size, GFP_NOFS);
> + if (!sample)
> + goto out;
> +
> + /* Read small subset of data 1024b-4096b */
> + a = 0; b = 0;
> + while (index <= end_index) {
> + page = find_get_page(inode->i_mapping, index);
> + input_data = kmap(page);
> + c = 0;
> + while (c < PAGE_SIZE - READ_SIZE) {
> + if (a >= input_size - READ_SIZE)
> + break;
> + if (b >= sample_size - READ_SIZE)
> + break;
> + memcpy(&sample[b], &input_data[c], READ_SIZE);
> + c += shift;
> + a += shift;
> + b += READ_SIZE;
> + }
> + kunmap(page);
> + put_page(page);
> + index++;
> + }
As mentioned in the previous mail, we'll add the skeleton code only for
now, which means this loop, that simply calls find_get_page, kunmap and
put_page.
> +
> + ret = ___btrfs_compress_heuristic(sample, sample_size);
> +
> +out:
> + kfree(sample);
> + return ret;
> +}
> diff --git a/fs/btrfs/heuristic.h b/fs/btrfs/heuristic.h
> new file mode 100644
> index 000000000000..3565a6219b2a
> --- /dev/null
> +++ b/fs/btrfs/heuristic.h
> @@ -0,0 +1,14 @@
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/fs.h>
> +
> +enum compression_advice {
> + COMPRESS_NONE,
> + COMPRESS_COST_UNKNOWN,
> + COMPRESS_COST_EASY,
> + COMPRESS_COST_MEDIUM,
> + COMPRESS_COST_HARD
I don't find the naming good, as the cost is not easy or hard, but
rather low/medium/high. Or you can rename the whole prefix if you find a
better naming scheme.
> +};
> +
> +enum compression_advice btrfs_compress_heuristic(struct inode *inode,
> + u64 start, u64 end);
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index ef3c98c527c1..19654a83da36 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -60,6 +60,7 @@
> #include "props.h"
> #include "qgroup.h"
> #include "dedupe.h"
> +#include "heuristic.h"
>
> struct btrfs_iget_args {
> struct btrfs_key *location;
> @@ -458,16 +459,16 @@ static noinline void compress_file_range(struct inode *inode,
> unsigned long total_compressed = 0;
> unsigned long total_in = 0;
> int i;
> - int will_compress;
> + bool will_compress;
Please remove this change.
> int compress_type = fs_info->compress_type;
> - int redirty = 0;
> + bool redirty = false;
And this.
> inode_should_defrag(BTRFS_I(inode), start, end, end - start + 1,
> SZ_16K);
>
> actual_end = min_t(u64, isize, end + 1);
> again:
> - will_compress = 0;
> + will_compress = false;
> nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
> BUILD_BUG_ON((BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0);
> nr_pages = min_t(unsigned long, nr_pages,
> @@ -510,15 +511,6 @@ static noinline void compress_file_range(struct inode *inode,
> */
> if (inode_need_compress(inode)) {
> WARN_ON(pages);
> - pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
> - if (!pages) {
> - /* just bail out to the uncompressed code */
> - goto cont;
> - }
> -
> - if (BTRFS_I(inode)->force_compress)
> - compress_type = BTRFS_I(inode)->force_compress;
> -
> /*
> * we need to call clear_page_dirty_for_io on each
> * page in the range. Otherwise applications with the file
> @@ -529,7 +521,23 @@ static noinline void compress_file_range(struct inode *inode,
> * dirty again later on.
> */
> extent_range_clear_dirty_for_io(inode, start, end);
> - redirty = 1;
> + redirty = true;
> +
> + ret = btrfs_compress_heuristic(inode, start, end);
> +
> + /* Heuristic say: dont try compress that */
> + if (!ret)
> + goto cont;
> +
> + pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
> + if (!pages) {
> + /* just bail out to the uncompressed code */
> + goto cont;
> + }
> +
> + if (BTRFS_I(inode)->force_compress)
> + compress_type = BTRFS_I(inode)->force_compress;
> +
> ret = btrfs_compress_pages(compress_type,
> inode->i_mapping, start,
> pages,
> @@ -552,7 +560,7 @@ static noinline void compress_file_range(struct inode *inode,
> PAGE_SIZE - offset);
> kunmap_atomic(kaddr);
> }
> - will_compress = 1;
> + will_compress = true;
> }
> }
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