https://github.com/ceph/ceph/blob/master/src/os/bluestore/KernelDevice.cc#L477 On 07/12/2016 10:36 AM, Somnath Roy wrote:
<< And another observation - the issue isn't reproduced with stupid allocator hence I suspect some bug in bitmap one I was about to co-relate that , it seems a bug in Bitamp allocator then. I need to check the memory growth is also related to Bitmap allocator related or not. I will do some digging. Thanks & Regards Somnath -----Original Message----- From: Igor Fedotov [mailto:ifedotov@xxxxxxxxxxxx] Sent: Tuesday, July 12, 2016 8:32 AM To: Somnath Roy; Mark Nelson; ceph-devel Subject: Re: bluestore onode diet and encoding overhead Somnath, yeah, you're right about db partition is getting out of space: -876> 2016-07-12 18:19:26.133795 7f8e6ddb7700 10 bluefs get_usage bdev 0 free 0 (0 B) / 268431360 (255 MB), used 100% -875> 2016-07-12 18:19:26.133796 7f8e6ddb7700 10 bluefs get_usage bdev 1 free 193986560 (185 MB) / 268427264 (255 MB), used 27% -874> 2016-07-12 18:19:26.133797 7f8e6ddb7700 10 bluefs get_usage bdev 2 free 1073741824 (1024 MB) / 1074782208 (1024 MB), used 0% And I don't see much RAM consumption in this case. But the curious thing about my test case is that it shouldn't increase amount of metadata written as I'm doing writes within the first megabyte only( see fio script I posted last week). Looks like somebody wastes DB space - usage at bdev 0 is constantly growing while I'm running the test case... And another observation - the issue isn't reproduced with stupid allocator hence I suspect some bug in bitmap one... Thanks, Igor On 12.07.2016 18:14, Somnath Roy wrote:Mark, Recently, the default allocator is changed to Bitmap and I saw it is returning < 0 return value only in the following case. count = m_bit_alloc->alloc_blocks_res(nblks, &start_blk); if (count == 0) { return -ENOSPC; } So, it seems it may not be the memory but db partition is getting out of space (?). I never faced it so far as I was running with 100GB of db partition may be. The amount of metadata write going on to the db even after onode diet is starting from ~1K and over time it is reaching > 4k or so (I checked for 4K RW). It is growing as extents are growing. So, 8 GB may not be enough. If this is true, next challenge is , how to automatically (or document) the size of rocksdb db partition based on the data partition size. For example, in the ZS case, we have calculated that we need ~9G db space per TB. We need to do similar calculation for rocksbd as well. Thanks & Regards Somnath -----Original Message----- From: Mark Nelson [mailto:mnelson@xxxxxxxxxx] Sent: Tuesday, July 12, 2016 6:03 AM To: Igor Fedotov; Somnath Roy; ceph-devel Subject: Re: bluestore onode diet and encoding overhead In this case I'm assigning per OSD: 1G Data (basically the top level OSD dir) 1G WAL 8G DB 140G Block Mark On 07/12/2016 07:57 AM, Igor Fedotov wrote:Mark, you can find my post named 'yet another assertion in bluestore during random write' last week. It contains steps to reproduce in my case. Also I did some investigations (still incomplete though) with tuning 'bluestore block db size' and 'bluestore block wal size'. Setting both to 256M fixes the issue for me. But I'm still uncertain if that's a bug or just inappropriate settings... Thanks, Igor On 12.07.2016 15:48, Mark Nelson wrote:Oh, that's good to know! Have you tracked it down at all? I noticed pretty extreme memory usage on the OSDs still, so that might be part of it. I'm doing a massif run now. Mark On 07/12/2016 07:40 AM, Igor Fedotov wrote:That's similar to what I have while running my test case with vstart... Without Somnath's settings though.. On 12.07.2016 15:34, Mark Nelson wrote:Hi Somnath, I accidentally screwed up my first run with your settings but reran last night. With your tuning the OSDs are failing to allocate to bdev0 after about 30 minutes of testing: 2016-07-12 03:48:51.127781 7f0cef8b7700 -1 bluefs _allocate failed to allocate 1048576 on bdev 0, free 0; fallback to bdev 1 They are able to continue running, but ultimately this leads to an assert later on. I wonder if it's not compacting fast enough and ends up consuming the entire disk with stale metadata. 2016-07-12 04:31:02.631982 7f0cef8b7700 -1 /home/ubuntu/src/markhpc/ceph/src/os/bluestore/BlueFS.cc: In function 'int BlueFS::_allocate(unsigned int, uint64_t, std::vector<bluefs_extent_t>*)' thread 7f0cef8b7700 time 2016-07-12 04:31:02.627138 /home/ubuntu/src/markhpc/ceph/src/os/bluestore/BlueFS.cc: 1398: FAILED assert(0 == "allocate failed... wtf") ceph version v10.0.4-6936-gc7da2f7 (c7da2f7c869694246650a9276a2b67aed9bf818f) 1: (ceph::__ceph_assert_fail(char const*, char const*, int, char const*)+0x85) [0xd4cb75] 2: (BlueFS::_allocate(unsigned int, unsigned long, std::vector<bluefs_extent_t, std::allocator<bluefs_extent_t>*)+0x760) [0xb98220]3: (BlueFS::_compact_log()+0xd5b) [0xb9b5ab] 4: (BlueFS::_maybe_compact_log()+0x2a0) [0xb9c040] 5: (BlueFS::sync_metadata()+0x20f) [0xb9d28f] 6: (BlueRocksDirectory::Fsync()+0xd) [0xbb2fad] 7: (rocksdb::DBImpl::WriteImpl(rocksdb::WriteOptions const&, rocksdb::WriteBatch*, rocksdb::WriteCallback*, unsigned long*, unsigned long, bool)+0x1456) [0xbfdb96] 8: (rocksdb::DBImpl::Write(rocksdb::WriteOptions const&, rocksdb::WriteBatch*)+0x27) [0xbfe7a7] 9: (RocksDBStore::submit_transaction_sync(std::shared_ptr<KeyValueDB:: TransactionImpl>)+0x6b) [0xb3df2b] 10: (BlueStore::_kv_sync_thread()+0xedb) [0xaf935b] 11: (BlueStore::KVSyncThread::entry()+0xd) [0xb21e8d] 12: (()+0x7dc5) [0x7f0d185c4dc5] 13: (clone()+0x6d) [0x7f0d164bf28d] NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this. On 07/12/2016 02:13 AM, Somnath Roy wrote:Thanks Mark ! Yes, quite similar result I am also seeing for 4K RW. BTW, did you get chance to try out the rocksdb tuning I posted earlier ? It may reduce the stalls in your environment. Regards Somnath -----Original Message----- From: ceph-devel-owner@xxxxxxxxxxxxxxx [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Nelson Sent: Tuesday, July 12, 2016 12:03 AM To: ceph-devel Subject: bluestore onode diet and encoding overhead Hi All, With Igor's patch last week I was able to get some bluestore performance runs in without segfaulting and started looking int the results. Somewhere along the line we really screwed up read performance, but that's another topic. Right now I want to focus on random writes. Before we put the onode on a diet we were seeing massive amounts of read traffic in RocksDB during compaction that caused write stalls during 4K random writes. Random write performance on fast hardware like NVMe devices was often below filestore at anything other than very large IO sizes. This was largely due to the size of the onode compounded with RocksDB's tendency toward read and write amplification. The new test results look very promising. We've dramatically improved performance of random writes at most IO sizes, so that they are now typically quite a bit higher than both filestore and older bluestore code. Unfortunately for very small IO sizes performance hasn't improved much. We are no longer seeing huge amounts of RocksDB read traffic and fewer write stalls. We are however seeing huge memory usage (~9GB RSS per OSD) and very high CPU usage. I think this confirms some of the memory issues somnath was continuing to see. I don't think it's a leak exactly based on how the OSDs were behaving, but we need to run through massif still to be sure. I ended up spending some time tonight with perf and digging through the encode code. I wrote up some notes with graphs and code snippets and decided to put them up on the web. Basically some of the encoding changes we implemented last month to reduce the onode size also appear to result in more buffer::list appends and the associated overhead. I've been trying to think through ways to improve the situation and thought other people might have some ideas too. Here's a link to the short writeup: https://drive.google.com/file/d/0B2gTBZrkrnpZeC04eklmM2I4Wkk/view? usp=sharing Thanks, Mark -- 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 PLEASE NOTE: The information contained in this electronic mail message is intended only for the use of the designated recipient(s) named above. 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