Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752591AbbEQBVT (ORCPT ); Sat, 16 May 2015 21:21:19 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:41411 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751768AbbEQBVK convert rfc822-to-8bit (ORCPT ); Sat, 16 May 2015 21:21:10 -0400 From: "Elliott, Robert (Server Storage)" To: Dan Williams , "linux-nvdimm@lists.01.org" CC: Ingo Molnar , Neil Brown , Greg KH , Dave Chinner , "linux-kernel@vger.kernel.org" , "Andy Lutomirski" , Jens Axboe , "H. Peter Anvin" , Christoph Hellwig , "Kani, Toshimitsu" Subject: RE: [Linux-nvdimm] [PATCH v2 19/20] nd_btt: atomic sector updates Thread-Topic: [Linux-nvdimm] [PATCH v2 19/20] nd_btt: atomic sector updates Thread-Index: AQHQgeErg/CZLhAojkO0AUlsrj19g51/c8AA Date: Sun, 17 May 2015 01:19:17 +0000 Message-ID: <94D0CD8314A33A4D9D801C0FE68B40295A9097E5@G9W0745.americas.hpqcorp.net> References: <20150428181203.35812.60474.stgit@dwillia2-desk3.amr.corp.intel.com> <20150428182557.35812.38292.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <20150428182557.35812.38292.stgit@dwillia2-desk3.amr.corp.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [16.210.48.26] Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7493 Lines: 169 > -----Original Message----- > From: Linux-nvdimm [mailto:linux-nvdimm-bounces@lists.01.org] On Behalf Of > Dan Williams > Sent: Tuesday, April 28, 2015 1:26 PM > To: linux-nvdimm@lists.01.org > Cc: Ingo Molnar; Neil Brown; Greg KH; Dave Chinner; linux- > kernel@vger.kernel.org; Andy Lutomirski; Jens Axboe; H. Peter Anvin; > Christoph Hellwig > Subject: [Linux-nvdimm] [PATCH v2 19/20] nd_btt: atomic sector updates > > From: Vishal Verma > > BTT stands for Block Translation Table, and is a way to provide power > fail sector atomicity semantics for block devices that have the ability > to perform byte granularity IO. It relies on the ->rw_bytes() capability > of provided nd namespace devices. > > The BTT works as a stacked blocked device, and reserves a chunk of space > from the backing device for its accounting metadata. BLK namespaces may > mandate use of a BTT and expect the bus to initialize a BTT if not > already present. Otherwise if a BTT is desired for other namespaces (or > partitions of a namespace) a BTT may be manually configured. ... Running btt above pmem with a variety of workloads, I see an awful lot of time spent in two places: * _raw_spin_lock * btt_make_request This occurs for fio to raw /dev/ndN devices, ddpt over ext4 or xfs, cp -R of large directories, and running make on the linux kernel. Some specific results: fio 4 KiB random reads, WC cache type, memcpy: * 43175 MB/s, 8 M IOPS pmem0 and pmem1 * 18500 MB/s, 1.5 M IOPS nd0 and nd1 fio 4 KiB random reads, WC cache type, memcpy with non-temporal loads (when everything is 64-byte aligned): * 33814 MB/s, 4.3 M IOPS nd0 and nd1 Zeroing out 32 MiB with ddpt: * 19 s, 1800 MiB/s pmem * 55 s, 625 MiB/s btt If btt_make_request needs to stall this much, maybe it'd be better to utilize the blk-mq request queues, keeping requests in per-CPU queues while they're waiting, and using IPIs for completion interrupts when they're finally done. fio 4 KiB random reads without non-temporal memcpy ================================================== perf top shows memcpy_erms taking all the time, a function that uses 8-byte REP; MOVSB instructions: 85.78% [kernel] [k] memcpy_erms 1.21% [kernel] [k] _raw_spin_lock 0.72% [nd_btt] [k] btt_make_request 0.67% [kernel] [k] do_blockdev_direct_IO 0.47% fio [.] get_io_u fio 4 KiB random reads with non-temporal memcpy =============================================== perf top shows there are still quite a few unaligned accesses resulting in legacy memcpy, but about equal time is now spent in legacy vs NT memcpy: 30.47% [kernel] [k] memcpy_erms 26.27% [kernel] [k] memcpy_lnt_st_64 5.37% [kernel] [k] _raw_spin_lock 2.20% [kernel] [k] btt_make_request 2.03% [kernel] [k] do_blockdev_direct_IO 1.41% fio [.] get_io_u 1.22% [kernel] [k] btt_map_read 1.15% [kernel] [k] pmem_rw_bytes 1.01% [kernel] [k] nd_btt_rw_bytes 0.98% [kernel] [k] nd_region_acquire_lane 0.89% fio [.] get_next_rand_block 0.88% fio [.] thread_main 0.79% fio [.] ios_completed 0.76% fio [.] td_io_queue 0.75% [kernel] [k] _raw_spin_lock_irqsave 0.68% [kernel] [k] kmem_cache_free 0.66% [kernel] [k] kmem_cache_alloc 0.59% [kernel] [k] __audit_syscall_exit 0.57% [kernel] [k] aio_complete 0.54% [kernel] [k] do_io_submit 0.52% [kernel] [k] _raw_spin_unlock_irqrestore fio randrw workload =================== perf top shows that adding writes to the mix brings btt_make_request its cpu_relax() loop to the forefront: 21.09% [nd_btt] [k] btt_make_request 19.06% [kernel] [k] memcpy_erms 14.35% [kernel] [k] _raw_spin_lock 10.38% [nd_pmem] [k] memcpy_lnt_st_64 1.57% [kernel] [k] do_blockdev_direct_IO 1.51% [nd_pmem] [k] memcpy_lt_snt_64 1.43% [nd_btt] [k] nd_btt_rw_bytes 1.39% [kernel] [k] radix_tree_next_chunk 1.33% [kernel] [k] put_page 1.21% [nd_pmem] [k] pmem_rw_bytes 1.11% fio [.] get_io_u 0.90% fio [.] io_u_queued_complete 0.74% [kernel] [k] system_call 0.72% [libnd] [k] nd_region_acquire_lane 0.71% [nd_btt] [k] btt_map_read 0.62% fio [.] thread_main inside btt_make_request: ? /* Wait if the new block is being read from */ ? for (i = 0; i < arena->nfree; i++) 2.98 ? ? je 2b4 0.05 ? mov 0x60(%r14),%rax 0.00 ? mov %ebx,%edx ? xor %esi,%esi 0.03 ? or $0x80000000,%edx 0.05 ? nop ? while (arena->rtt[i] == (RTT_VALID | new_postmap)) 22.98 ?290: mov %esi,%edi 0.01 ? cmp %edx,(%rax,%rdi,4) 30.97 ? lea 0x0(,%rdi,4),%rcx 21.05 ? ? jne 2ab ? nop ? } ? ? /* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */ ? static inline void rep_nop(void) ? { ? asm volatile("rep; nop" ::: "memory"); ?2a0: pause ? mov 0x60(%r14),%rax ? cmp (%rax,%rcx,1),%edx ? ? je 2a0 ? } ddpt zeroing out ================ perf top shows 27% in spinlocks, and 14% in btt_make_request (all in the "wait if the new block is being read from" loop). 26.48% [kernel] [k] _raw_spin_lock 14.46% [nd_btt] [k] btt_make_request 13.14% [kernel] [k] memcpy_erms 10.34% [kernel] [k] copy_user_enhanced_fast_string 3.12% [nd_pmem] [k] memcpy_lt_snt_64 1.15% [kernel] [k] __block_commit_write.isra.21 0.96% [nd_pmem] [k] pmem_rw_bytes 0.96% [nd_btt] [k] nd_btt_rw_bytes 0.86% [kernel] [k] unlock_page 0.65% [kernel] [k] _raw_spin_lock_irqsave 0.58% [kernel] [k] bdev_read_only 0.56% [kernel] [k] release_pages 0.54% [nd_pmem] [k] memcpy_lnt_st_64 0.53% [ext4] [k] ext4_mark_iloc_dirty 0.52% [kernel] [k] __wake_up_bit 0.52% [kernel] [k] __clear_user --- Robert Elliott, HP Server Storage -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/