From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42117) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ejNwP-0002Gg-2I for qemu-devel@nongnu.org; Wed, 07 Feb 2018 06:31:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ejNwL-0007Eu-4V for qemu-devel@nongnu.org; Wed, 07 Feb 2018 06:31:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55854) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ejNwK-0007Ec-RA for qemu-devel@nongnu.org; Wed, 07 Feb 2018 06:31:01 -0500 Date: Wed, 7 Feb 2018 06:30:59 -0500 (EST) From: Pankaj Gupta Message-ID: <1088873740.1160580.1518003059555.JavaMail.zimbra@redhat.com> In-Reply-To: <20180207111855.2o2zq3evrkwypomw@hz-desktop> References: <20180207073331.14158-1-haozhong.zhang@intel.com> <20180207073331.14158-6-haozhong.zhang@intel.com> <1091122025.1148119.1517998640676.JavaMail.zimbra@redhat.com> <20180207111855.2o2zq3evrkwypomw@hz-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 5/8] migration/ram: ensure write persistence on loading zero pages to PMEM List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Haozhong Zhang Cc: qemu-devel@nongnu.org, Xiao Guangrong , mst@redhat.com, Juan Quintela , dgilbert@redhat.com, Stefan Hajnoczi , Paolo Bonzini , Igor Mammedov , Dan Williams , Eduardo Habkost > > On 02/07/18 05:17 -0500, Pankaj Gupta wrote: > > > > > > > > When loading a zero page, check whether it will be loaded to > > > persistent memory If yes, load it by libpmem function > > > pmem_memset_nodrain(). Combined with a call to pmem_drain() at the > > > end of RAM loading, we can guarantee all those zero pages are > > > persistently loaded. > > > > > > Depending on the host HW/SW configurations, pmem_drain() can be > > > "sfence". Therefore, we do not call pmem_drain() after each > > > pmem_memset_nodrain(), or use pmem_memset_persist() (equally > > > pmem_memset_nodrain() + pmem_drain()), in order to avoid unnecessary > > > overhead. > > > > Are you saying we don't need 'pmem_drain()'? > > pmem_drain() is called only once after all ram blocks are loaded. o.k > > > > > I can see its called in patch 5 in ram_load? But > > I also see empty definition. Anything I am missing here? > > Functions defined in include/qemu/pmem.h are stubs and used only when > QEMU is not compiled with libpmem. When QEMU is compiled with > --enabled-libpmem, the one in libpmem is used. p.k. Thanks, Pankaj > > Haozhong > > > > > Thanks, > > Pankaj > > > > > > > > Signed-off-by: Haozhong Zhang > > > --- > > > include/qemu/pmem.h | 9 +++++++++ > > > migration/ram.c | 34 +++++++++++++++++++++++++++++----- > > > 2 files changed, 38 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/qemu/pmem.h b/include/qemu/pmem.h > > > index 9017596ff0..861d8ecc21 100644 > > > --- a/include/qemu/pmem.h > > > +++ b/include/qemu/pmem.h > > > @@ -26,6 +26,15 @@ pmem_memcpy_persist(void *pmemdest, const void *src, > > > size_t len) > > > return memcpy(pmemdest, src, len); > > > } > > > > > > +static inline void *pmem_memset_nodrain(void *pmemdest, int c, size_t > > > len) > > > +{ > > > + return memset(pmemdest, c, len); > > > +} > > > + > > > +static inline void pmem_drain(void) > > > +{ > > > +} > > > + > > > #endif /* CONFIG_LIBPMEM */ > > > > > > #endif /* !QEMU_PMEM_H */ > > > diff --git a/migration/ram.c b/migration/ram.c > > > index cb1950f3eb..5a0e503818 100644 > > > --- a/migration/ram.c > > > +++ b/migration/ram.c > > > @@ -49,6 +49,7 @@ > > > #include "qemu/rcu_queue.h" > > > #include "migration/colo.h" > > > #include "migration/block.h" > > > +#include "qemu/pmem.h" > > > > > > /***********************************************************/ > > > /* ram save/restore */ > > > @@ -2467,6 +2468,20 @@ static inline void > > > *host_from_ram_block_offset(RAMBlock *block, > > > return block->host + offset; > > > } > > > > > > +static void ram_handle_compressed_common(void *host, uint8_t ch, > > > uint64_t > > > size, > > > + bool is_pmem) > > > +{ > > > + if (!ch && is_zero_range(host, size)) { > > > + return; > > > + } > > > + > > > + if (!is_pmem) { > > > + memset(host, ch, size); > > > + } else { > > > + pmem_memset_nodrain(host, ch, size); > > > + } > > > +} > > > + > > > /** > > > * ram_handle_compressed: handle the zero page case > > > * > > > @@ -2479,9 +2494,7 @@ static inline void > > > *host_from_ram_block_offset(RAMBlock > > > *block, > > > */ > > > void ram_handle_compressed(void *host, uint8_t ch, uint64_t size) > > > { > > > - if (ch != 0 || !is_zero_range(host, size)) { > > > - memset(host, ch, size); > > > - } > > > + return ram_handle_compressed_common(host, ch, size, false); > > > } > > > > > > static void *do_data_decompress(void *opaque) > > > @@ -2823,6 +2836,7 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > bool postcopy_running = postcopy_is_running(); > > > /* ADVISE is earlier, it shows the source has the postcopy > > > capability on > > > */ > > > bool postcopy_advised = postcopy_is_advised(); > > > + bool need_pmem_drain = false; > > > > > > seq_iter++; > > > > > > @@ -2848,6 +2862,8 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > ram_addr_t addr, total_ram_bytes; > > > void *host = NULL; > > > uint8_t ch; > > > + RAMBlock *block = NULL; > > > + bool is_pmem = false; > > > > > > addr = qemu_get_be64(f); > > > flags = addr & ~TARGET_PAGE_MASK; > > > @@ -2864,7 +2880,7 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > > > > if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE | > > > RAM_SAVE_FLAG_COMPRESS_PAGE | > > > RAM_SAVE_FLAG_XBZRLE)) { > > > - RAMBlock *block = ram_block_from_stream(f, flags); > > > + block = ram_block_from_stream(f, flags); > > > > > > host = host_from_ram_block_offset(block, addr); > > > if (!host) { > > > @@ -2874,6 +2890,9 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > } > > > ramblock_recv_bitmap_set(block, host); > > > trace_ram_load_loop(block->idstr, (uint64_t)addr, flags, > > > host); > > > + > > > + is_pmem = ramblock_is_pmem(block); > > > + need_pmem_drain = need_pmem_drain || is_pmem; > > > } > > > > > > switch (flags & ~RAM_SAVE_FLAG_CONTINUE) { > > > @@ -2927,7 +2946,7 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > > > > case RAM_SAVE_FLAG_ZERO: > > > ch = qemu_get_byte(f); > > > - ram_handle_compressed(host, ch, TARGET_PAGE_SIZE); > > > + ram_handle_compressed_common(host, ch, TARGET_PAGE_SIZE, > > > is_pmem); > > > break; > > > > > > case RAM_SAVE_FLAG_PAGE: > > > @@ -2970,6 +2989,11 @@ static int ram_load(QEMUFile *f, void *opaque, int > > > version_id) > > > } > > > > > > wait_for_decompress_done(); > > > + > > > + if (need_pmem_drain) { > > > + pmem_drain(); > > > + } > > > + > > > rcu_read_unlock(); > > > trace_ram_load_complete(ret, seq_iter); > > > return ret; > > > -- > > > 2.14.1 > > > > > > > > > >