From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48904) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d80TZ-0001Eo-Nd for qemu-devel@nongnu.org; Tue, 09 May 2017 04:26:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d80TV-0007p4-O6 for qemu-devel@nongnu.org; Tue, 09 May 2017 04:26:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35214) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d80TV-0007oi-FD for qemu-devel@nongnu.org; Tue, 09 May 2017 04:26:29 -0400 Date: Tue, 9 May 2017 16:26:22 +0800 From: Peter Xu Message-ID: <20170509082622.GI2820@pxdev.xzpeter.org> References: <1493362658-8179-1-git-send-email-a.perevalov@samsung.com> <1493362658-8179-6-git-send-email-a.perevalov@samsung.com> <20170428100012.GB22801@pxdev.xzpeter.org> <20170508062906.GC2820@pxdev.xzpeter.org> <20170508090807.GA4201@aperevalov-ubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170508090807.GA4201@aperevalov-ubuntu> Subject: Re: [Qemu-devel] [PATCH RESEND V3 5/6] migration: calculate downtime on dst side List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Cc: i.maximets@samsung.com, f4bug@amsat.org, qemu-devel@nongnu.org, dgilbert@redhat.com On Mon, May 08, 2017 at 12:08:07PM +0300, Alexey wrote: > On Mon, May 08, 2017 at 02:29:06PM +0800, Peter Xu wrote: > > On Fri, Apr 28, 2017 at 02:11:19PM +0300, Alexey Perevalov wrote: > > > On 04/28/2017 01:00 PM, Peter Xu wrote: > > > >On Fri, Apr 28, 2017 at 09:57:37AM +0300, Alexey Perevalov wrote: > > > >>This patch provides downtime calculation per vCPU, > > > >>as a summary and as a overlapped value for all vCPUs. > > > >> > > > >>This approach was suggested by Peter Xu, as an improvements of > > > >>previous approch where QEMU kept tree with faulted page address and cpus bitmask > > > >>in it. Now QEMU is keeping array with faulted page address as value and vCPU > > > >>as index. It helps to find proper vCPU at UFFD_COPY time. Also it keeps > > > >>list for downtime per vCPU (could be traced with page_fault_addr) > > > >> > > > >>For more details see comments for get_postcopy_total_downtime > > > >>implementation. > > > >> > > > >>Downtime will not calculated if postcopy_downtime field of > > > >>MigrationIncomingState wasn't initialized. > > > >> > > > >>Signed-off-by: Alexey Perevalov > > > >>--- > > > >> include/migration/migration.h | 3 ++ > > > >> migration/migration.c | 103 ++++++++++++++++++++++++++++++++++++++++++ > > > >> migration/postcopy-ram.c | 20 +++++++- > > > >> migration/trace-events | 6 ++- > > > >> 4 files changed, 130 insertions(+), 2 deletions(-) > > > >> > > > >>diff --git a/include/migration/migration.h b/include/migration/migration.h > > > >>index e8fb68f..a22f9ce 100644 > > > >>--- a/include/migration/migration.h > > > >>+++ b/include/migration/migration.h > > > >>@@ -139,6 +139,9 @@ void migration_incoming_state_destroy(void); > > > >> * Functions to work with downtime context > > > >> */ > > > >> struct DowntimeContext *downtime_context_new(void); > > > >>+void mark_postcopy_downtime_begin(uint64_t addr, int cpu); > > > >>+void mark_postcopy_downtime_end(uint64_t addr); > > > >>+uint64_t get_postcopy_total_downtime(void); > > > >> struct MigrationState > > > >> { > > > >>diff --git a/migration/migration.c b/migration/migration.c > > > >>index ec76e5c..2c6f150 100644 > > > >>--- a/migration/migration.c > > > >>+++ b/migration/migration.c > > > >>@@ -2150,3 +2150,106 @@ PostcopyState postcopy_state_set(PostcopyState new_state) > > > >> return atomic_xchg(&incoming_postcopy_state, new_state); > > > >> } > > > >>+void mark_postcopy_downtime_begin(uint64_t addr, int cpu) > > > >>+{ > > > >>+ MigrationIncomingState *mis = migration_incoming_get_current(); > > > >>+ DowntimeContext *dc; > > > >>+ if (!mis->downtime_ctx || cpu < 0) { > > > >>+ return; > > > >>+ } > > > >>+ dc = mis->downtime_ctx; > > > >>+ dc->vcpu_addr[cpu] = addr; > > > >>+ dc->last_begin = dc->page_fault_vcpu_time[cpu] = > > > >>+ qemu_clock_get_ms(QEMU_CLOCK_REALTIME); > > > >>+ > > > >>+ trace_mark_postcopy_downtime_begin(addr, dc, dc->page_fault_vcpu_time[cpu], > > > >>+ cpu); > > > >>+} > > > >>+ > > > >>+void mark_postcopy_downtime_end(uint64_t addr) > > > >>+{ > > > >>+ MigrationIncomingState *mis = migration_incoming_get_current(); > > > >>+ DowntimeContext *dc; > > > >>+ int i; > > > >>+ bool all_vcpu_down = true; > > > >>+ int64_t now; > > > >>+ > > > >>+ if (!mis->downtime_ctx) { > > > >>+ return; > > > >>+ } > > > >>+ dc = mis->downtime_ctx; > > > >>+ now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); > > > >>+ > > > >>+ /* check all vCPU down, > > > >>+ * QEMU has bitmap.h, but even with bitmap_and > > > >>+ * will be a cycle */ > > > >>+ for (i = 0; i < smp_cpus; i++) { > > > >>+ if (dc->vcpu_addr[i]) { > > > >>+ continue; > > > >>+ } > > > >>+ all_vcpu_down = false; > > > >>+ break; > > > >>+ } > > > >>+ > > > >>+ if (all_vcpu_down) { > > > >>+ dc->total_downtime += now - dc->last_begin; > > > >Shall we do this accouting only if we are sure the copied page address > > > >is one of the page faulted addresses? Can it be some other page? I > > > >don't know. But since we have the loop below to make sure of it, why > > > >not? > > > no, the downtime implies since page fault till the > > > page will be copied. > > > Yes another pages could be copied as well as pagefaulted, > > > and they are copied due to prefetching, but it's not a downtime. > > > > Not sure I got the point... Do you mean that when reach here, then > > this page address is definitely one of the faulted addresses? I am not > > 100% sure of this, but if you are sure, I am okay with it. > Let me clarify. > > > > >Shall we do this accouting only if we are sure the copied page address > > > >is one of the page faulted addresses? > Yes it's primary condition, due to there are could be another pages, > which weren't faulted, they just was sent from source to destination, > I called it prefetching. > > I think I got why did you ask that question, because in this version > all_vcpu_down and as a result total_downtime calculated incorrectly, > it calculates every time when any page is copied, but it should > be calculated only when faulted page copied, so only dc->vcpu_downtime > was correctly calculated. Exactly. I am afraid if we have such "prefetching" stuff then total_downtime will be more than its real value. -- Peter Xu