From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44014) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1esvHJ-0000t3-Qk for qemu-devel@nongnu.org; Mon, 05 Mar 2018 13:56:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1esvHF-0004xU-QL for qemu-devel@nongnu.org; Mon, 05 Mar 2018 13:56:05 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51888 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1esvHF-0004wb-Ln for qemu-devel@nongnu.org; Mon, 05 Mar 2018 13:56:01 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 063EDEBFE5 for ; Mon, 5 Mar 2018 18:55:59 +0000 (UTC) Date: Mon, 5 Mar 2018 18:55:45 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180305185544.GU3131@work-vm> References: <20180216131625.9639-1-dgilbert@redhat.com> <20180216131625.9639-18-dgilbert@redhat.com> <20180228100356.GE27381@xz-mi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180228100356.GE27381@xz-mi> Subject: Re: [Qemu-devel] [PATCH v3 17/29] vhost+postcopy: Send requests to source for shared pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel@nongnu.org, maxime.coquelin@redhat.com, marcandre.lureau@redhat.com, imammedo@redhat.com, mst@redhat.com, quintela@redhat.com, aarcange@redhat.com * Peter Xu (peterx@redhat.com) wrote: > On Fri, Feb 16, 2018 at 01:16:13PM +0000, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > Send requests back to the source for shared page requests. > > > > Signed-off-by: Dr. David Alan Gilbert > > --- > > migration/migration.h | 2 ++ > > migration/postcopy-ram.c | 31 ++++++++++++++++++++++++++++--- > > migration/postcopy-ram.h | 3 +++ > > migration/trace-events | 2 ++ > > 4 files changed, 35 insertions(+), 3 deletions(-) > > > > diff --git a/migration/migration.h b/migration/migration.h > > index d158e62cf2..457bf37ec2 100644 > > --- a/migration/migration.h > > +++ b/migration/migration.h > > @@ -46,6 +46,8 @@ struct MigrationIncomingState { > > int userfault_quit_fd; > > QEMUFile *to_src_file; > > QemuMutex rp_mutex; /* We send replies from multiple threads */ > > + /* RAMBlock of last request sent to source */ > > + RAMBlock *last_rb; > > void *postcopy_tmp_page; > > void *postcopy_tmp_zero_page; > > /* PostCopyFD's for external userfaultfds & handlers of shared memory */ > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > > index d118b78bf5..277ff749a0 100644 > > --- a/migration/postcopy-ram.c > > +++ b/migration/postcopy-ram.c > > @@ -534,6 +534,31 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, > > return 0; > > } > > > > +/* > > + * Callback from shared fault handlers to ask for a page, > > + * the page must be specified by a RAMBlock and an offset in that rb > > + */ > > +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, > > + uint64_t client_addr, uint64_t rb_offset) > > +{ > > + size_t pagesize = qemu_ram_pagesize(rb); > > + uint64_t aligned_rbo = rb_offset & ~(pagesize - 1); > > + MigrationIncomingState *mis = migration_incoming_get_current(); > > + > > + trace_postcopy_request_shared_page(pcfd->idstr, qemu_ram_get_idstr(rb), > > + rb_offset); > > + /* TODO: Check bitmap to see if we already have the page */ > > + if (rb != mis->last_rb) { > > + mis->last_rb = rb; > > + migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb), > > + aligned_rbo, pagesize); > > + } else { > > + /* Save some space */ > > + migrate_send_rp_req_pages(mis, NULL, aligned_rbo, pagesize); > > + } > > + return 0; > > +} > > + > > So IIUC this can only be called within the page fault thread or there > can be race. Is there a way to guarantee this? Or do we need a > comment for that? I don't think there's a way to guarantee it - especially since it has to be called by the device-specific shared handlers in another file - I've updated the comment to: /* * Callback from shared fault handlers to ask for a page, * the page must be specified by a RAMBlock and an offset in that rb * Note: Only for use by shared fault handlers (in fault thread) */ Dave > > /* > > * Handle faults detected by the USERFAULT markings > > */ > > @@ -544,9 +569,9 @@ static void *postcopy_ram_fault_thread(void *opaque) > > int ret; > > size_t index; > > RAMBlock *rb = NULL; > > - RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */ > > > > trace_postcopy_ram_fault_thread_entry(); > > + mis->last_rb = NULL; /* last RAMBlock we sent part of */ > > qemu_sem_post(&mis->fault_thread_sem); > > > > struct pollfd *pfd; > > @@ -634,8 +659,8 @@ static void *postcopy_ram_fault_thread(void *opaque) > > * Send the request to the source - we want to request one > > * of our host page sizes (which is >= TPS) > > */ > > - if (rb != last_rb) { > > - last_rb = rb; > > + if (rb != mis->last_rb) { > > + mis->last_rb = rb; > > migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb), > > rb_offset, qemu_ram_pagesize(rb)); > > } else { > > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h > > index dbc2ee1f2b..4c63f20df4 100644 > > --- a/migration/postcopy-ram.h > > +++ b/migration/postcopy-ram.h > > @@ -162,5 +162,8 @@ struct PostCopyFD { > > */ > > void postcopy_register_shared_ufd(struct PostCopyFD *pcfd); > > void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd); > > +/* Callback from shared fault handlers to ask for a page */ > > +int postcopy_request_shared_page(struct PostCopyFD *pcfd, RAMBlock *rb, > > + uint64_t client_addr, uint64_t offset); > > > > #endif > > diff --git a/migration/trace-events b/migration/trace-events > > index 1e617ad7a6..7c910b5479 100644 > > --- a/migration/trace-events > > +++ b/migration/trace-events > > @@ -198,6 +198,8 @@ postcopy_ram_incoming_cleanup_closeuf(void) "" > > postcopy_ram_incoming_cleanup_entry(void) "" > > postcopy_ram_incoming_cleanup_exit(void) "" > > postcopy_ram_incoming_cleanup_join(void) "" > > +postcopy_request_shared_page(const char *sharer, const char *rb, uint64_t rb_offset) "for %s in %s offset 0x%"PRIx64 > > + > > save_xbzrle_page_skipping(void) "" > > save_xbzrle_page_overflow(void) "" > > ram_save_iterate_big_wait(uint64_t milliconds, int iterations) "big wait: %" PRIu64 " milliseconds, %d iterations" > > -- > > 2.14.3 > > > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK