Hi Qi, We don't write wal directly into wal device. wal is put into rocksdb to ensure consistency, and is submitted in "kv_sync_thread"(https://github.com/ceph/ceph/blob/master/src/os/bluestore/BlueStore.cc#L7582). We can configure a separated device/partition for rocksdb here(https://github.com/ceph/ceph/blob/master/src/common/config_opts.h#L1044) to store rocksdb wal. That is the wal device you mentioned. Thanks, Haodong On 1 April 2017 at 15:20, qi Shi <m13913886148@xxxxxxxxx> wrote: > hello everyone! > when bluestore is overwrite ,it will use wal. > and i think it is like journal. IO divided into submit and apply. > When i look at the code, i find _wal_apply(). > But i can not find wal submit. > I only found the following code : > --------------------------------------------------------------------------------------------------------------------- > // chunk-aligned wal overwrite? > if (b->get_blob().get_ondisk_length() >= b_off + b_len && > b_off % chunk_size == 0 && > b_len % chunk_size == 0 && > b->get_blob().is_allocated(b_off, b_len)) { > bluestore_wal_op_t *op = _get_wal_op(txc, o); > op->op = bluestore_wal_op_t::OP_WRITE; > _buffer_cache_write(txc, b, b_off, padded, > wctx->buffered ? 0 : Buffer::FLAG_NOCACHE); > > int r = b->get_blob().map( > b_off, b_len, > [&](uint64_t offset, uint64_t length) { > op->extents.emplace_back(bluestore_pextent_t(offset, length)); > return 0; > }); > assert(r == 0); > if (b->get_blob().csum_type) { > b->dirty_blob().calc_csum(b_off, padded); > } > op->data.claim(padded); > dout(20) << __func__ << " wal write 0x" << std::hex << b_off << "~" > << b_len << std::dec << " of mutable " << *b > << " at " << op->extents << dendl; > Extent *le = o->extent_map.set_lextent(offset, offset - bstart, length, > b, &wctx->old_extents); > b->dirty_blob().mark_used(le->blob_offset, le->length); > txc->statfs_delta.stored() += le->length; > dout(20) << __func__ << " lex " << *le << dendl; > logger->inc(l_bluestore_write_small_wal); > return; > ------------------------------------------------------------------------------------------------------------------- > > but these code does not write Block device partition of wal. > how does Bluestore submit IO to Block device partition of wal ? > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
