Hi Janne,
See below:
On 15/09/2014 17:55, Janne Grunau wrote:
> Requiring page aligned buffers and realigning the input if necessary
> creates measurable oberhead. ceph_erasure_code_benchmark is ~30% faster
> with this change for technique=reed_sol_van,k=2,m=1.
>
> Also prevents a misaligned buffer when bufferlist::c_str(bufferlist)
> has to allocate a new buffer to provide continuous one. See bug #9408
>
> Signed-off-by: Janne Grunau <j@xxxxxxxxxx>
> ---
> src/erasure-code/ErasureCode.cc | 46 +++++++++++++++++++++++++----------------
> src/erasure-code/ErasureCode.h | 3 ++-
> 2 files changed, 30 insertions(+), 19 deletions(-)
>
> diff --git a/src/erasure-code/ErasureCode.cc b/src/erasure-code/ErasureCode.cc
> index 5953f49..078f60b 100644
> --- a/src/erasure-code/ErasureCode.cc
> +++ b/src/erasure-code/ErasureCode.cc
> @@ -54,22 +54,38 @@ int ErasureCode::minimum_to_decode_with_cost(const set<int> &want_to_read,
> }
>
> int ErasureCode::encode_prepare(const bufferlist &raw,
> - bufferlist *prepared) const
> + map<int, bufferlist> &encoded) const
> {
> unsigned int k = get_data_chunk_count();
> unsigned int m = get_chunk_count() - k;
> unsigned blocksize = get_chunk_size(raw.length());
> - unsigned padded_length = blocksize * k;
> - *prepared = raw;
> - if (padded_length - raw.length() > 0) {
> - bufferptr pad(padded_length - raw.length());
> - pad.zero();
> - prepared->push_back(pad);
> + unsigned pad_len = blocksize * k - raw.length();
> +
> + bufferlist prepared = raw;
> +
> + if (!prepared.is_aligned()) {
> + prepared.rebuild_aligned();
> + }
> +
> + for (unsigned int i = 0; i < k - !!pad_len; i++) {
> + int chunk_index = chunk_mapping.size() > 0 ? chunk_mapping[i] : i;
> + bufferlist &chunk = encoded[chunk_index];
> + chunk.substr_of(prepared, i * blocksize, blocksize);
> + }
It is possible for more than one chunk to be padding. It's a border case but... for instance with alignment = 16, k=12 and in of length 1550 you end up with two padding chunks because the blocksize is 144.
> + if (pad_len > 0) {
> + int chunk_index = chunk_mapping.size() > 0 ? chunk_mapping[k - 1] : k - 1;
> + bufferlist &chunk = encoded[chunk_index];
> + bufferptr padded(buffer::create_aligned(blocksize));
> + raw.copy((k - 1) * blocksize, blocksize - pad_len, padded.c_str());
> + padded.zero(blocksize - pad_len, pad_len);
> + chunk.push_back(padded);
> }
> - unsigned coding_length = blocksize * m;
> - bufferptr coding(buffer::create_page_aligned(coding_length));
> - prepared->push_back(coding);
> - prepared->rebuild_page_aligned();
> + for (unsigned int i = k; i < k + m; i++) {
> + int chunk_index = chunk_mapping.size() > 0 ? chunk_mapping[i] : i;
> + bufferlist &chunk = encoded[chunk_index];
> + chunk.push_back(buffer::create_aligned(blocksize));
> + }
> +
> return 0;
> }
>
> @@ -80,15 +96,9 @@ int ErasureCode::encode(const set<int> &want_to_encode,
> unsigned int k = get_data_chunk_count();
> unsigned int m = get_chunk_count() - k;
> bufferlist out;
> - int err = encode_prepare(in, &out);
> + int err = encode_prepare(in, *encoded);
> if (err)
> return err;
> - unsigned blocksize = get_chunk_size(in.length());
> - for (unsigned int i = 0; i < k + m; i++) {
> - int chunk_index = chunk_mapping.size() > 0 ? chunk_mapping[i] : i;
> - bufferlist &chunk = (*encoded)[chunk_index];
> - chunk.substr_of(out, i * blocksize, blocksize);
> - }
> encode_chunks(want_to_encode, encoded);
> for (unsigned int i = 0; i < k + m; i++) {
> if (want_to_encode.count(i) == 0)
> diff --git a/src/erasure-code/ErasureCode.h b/src/erasure-code/ErasureCode.h
> index 7aaea95..62aa383 100644
> --- a/src/erasure-code/ErasureCode.h
> +++ b/src/erasure-code/ErasureCode.h
> @@ -46,7 +46,8 @@ namespace ceph {
> const map<int, int> &available,
> set<int> *minimum);
>
> - int encode_prepare(const bufferlist &raw, bufferlist *prepared) const;
> + int encode_prepare(const bufferlist &raw,
> + map<int, bufferlist> &encoded) const;
>
> virtual int encode(const set<int> &want_to_encode,
> const bufferlist &in,
>
--
Loïc Dachary, Artisan Logiciel Libre
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