I see it .Thanks very much! Jianpeng > -----Original Message----- > From: Loic Dachary [mailto:l...@dachary.org] > Sent: Tuesday, September 16, 2014 3:55 PM > To: Ma, Jianpeng > Cc: ceph-devel@vger.kernel.org > Subject: Re: [PATCH 2/3] ec: make use of added aligned buffers > > > > On 16/09/2014 08:59, Ma, Jianpeng wrote: > >> -----Original Message----- > >> From: Loic Dachary [mailto:l...@dachary.org] > >> Sent: Tuesday, September 16, 2014 2:47 PM > >> To: Ma, Jianpeng > >> Cc: ceph-devel@vger.kernel.org > >> Subject: Re: [PATCH 2/3] ec: make use of added aligned buffers > >> > >> > >> > >> On 16/09/2014 02:08, Ma, Jianpeng wrote: > >>>> -----Original Message----- > >>>> From: Sage Weil [mailto:sw...@redhat.com] > >>>> Sent: Tuesday, September 16, 2014 8:02 AM > >>>> To: Ma, Jianpeng > >>>> Cc: Loic Dachary; Janne Grunau; ceph-devel@vger.kernel.org > >>>> Subject: RE: [PATCH 2/3] ec: make use of added aligned buffers > >>>> > >>>> On Mon, 15 Sep 2014, Ma, Jianpeng wrote: > >>>>> If we modify bufferlist::c_str() to bufferlist::c_str(bool align). > >>>>> If (align) > >>>>> Posix_memalign(data, CEPH_PAGE_SIZE, len) Else > >>>>> Origin code. > >>>> > >>>> Alignment isn't really a bool, it's an int. c_str(int align=1) ? > >>>> > >>> I mean if we need a align memory after bufferlist::c_str. We can set > >>> the align = true; Now bufferlist::c_str depend on the size when > >>> using rebuild if > >> bufferlist have more prt. > >>> > >>> BTW, we also can change the rebuild() && rebuild(ptr). Merge two > >>> func into > >> one rebuild(bool align). > >>> By judge the parameter align to alloc align memory or not. > >>> > >>> Or am I missing something? > >> > >> I don't think there is a need for c_str(int align). We make every > >> effort to allocate buffers that are properly aligned. If c_str() does > >> not return an aligned buffer, the proper fix is to align the > >> allocated buffer at the source, not to allocate a new aligned buffer and > >> copy > the content of the non aligned buffer into it. > >> > > > >> Do you see a reason why that would be a bad way to deal with alignment ? > > We only guarantee memory align after c_str and don't depend on the > previous steps. > > This is a benefit indeed: less room for error in general. > > > If encode[i] have more ptr suppose they all aligned memory. > > But how to guarantee aligned memory after c_str. > > If bufferlist have more ptr, the aligned memory depend on the size of > bufferlist. > > The ErasureCode::encode_prepare prepares the allocated buffer so that > > *) it holds enough room to contain all chunks > *) c_str() on a chunk boundary will return a pointer that does not require > allocating memory > > The ErasureCodeJerasure::get_chunk_size function determines the size of the > buffer allocated by encode_prepare and further guarantees that each chunk is: > > *) size aligned on 16 bytes > *) memory aligned on 16 bytes so that SIMD instructions can use it without > moving it > > In other words, if c_str() had to re-allocate the buffer because it is not > aligned, > it would mean that the allocation of the buffer is not done as it should. >
> Cheers > > > Jianpeng > >> > >> Cheers > >> > >>> > >>> Jianpeng > >>>> sage > >>>> > >>>>> > >>>>> I think this is simple and correctly code. > >>>>> > >>>>> Jianpeng > >>>>> Thanks! > >>>>> > >>>>>> -----Original Message----- > >>>>>> From: ceph-devel-ow...@vger.kernel.org > >>>>>> [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Loic > >>>>>> Dachary > >>>>>> Sent: Tuesday, September 16, 2014 1:20 AM > >>>>>> To: Janne Grunau; ceph-devel@vger.kernel.org > >>>>>> Subject: Re: [PATCH 2/3] ec: make use of added aligned buffers > >>>>>> > >>>>>> 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...@jannau.net> > >>>>>>> --- > >>>>>>> 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, > >>>>>>> > >>>>>> > >>>>>> -- > >>>>>> Lo?c Dachary, Artisan Logiciel Libre > >>>>> > >>>>> -- > >>>>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" > >>>>> in the body of a message to majord...@vger.kernel.org More > >>>>> majordomo info at http://vger.kernel.org/majordomo-info.html > >>>>> > >>>>> > >>> -- > >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" > >>> in the body of a message to majord...@vger.kernel.org More majordomo > >>> info at http://vger.kernel.org/majordomo-info.html > >>> > >> > >> -- > >> Loïc Dachary, Artisan Logiciel Libre > > > > -- > > To unsubscribe from this list: send the line "unsubscribe ceph-devel" > > in the body of a message to majord...@vger.kernel.org More majordomo > > info at http://vger.kernel.org/majordomo-info.html > > > > -- > Loïc Dachary, Artisan Logiciel Libre -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
