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Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNEC
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect |
Date: |
Fri, 11 May 2018 19:03:35 +0100 |
User-agent: |
Mutt/1.9.5 (2018-04-13) |
* 858585 jemmy (address@hidden) wrote:
> On Wed, May 9, 2018 at 2:40 AM, Dr. David Alan Gilbert
> <address@hidden> wrote:
> > * Lidong Chen (address@hidden) wrote:
> >> When cancel migration during RDMA precopy, the source qemu main thread
> >> hangs sometime.
> >>
> >> The backtrace is:
> >> (gdb) bt
> >> #0 0x00007f249eabd43d in write () from /lib64/libpthread.so.0
> >> #1 0x00007f24a1ce98e4 in rdma_get_cm_event (channel=0x4675d10,
> >> event=0x7ffe2f643dd0) at src/cma.c:2189
> >> #2 0x00000000007b6166 in qemu_rdma_cleanup (rdma=0x6784000) at
> >> migration/rdma.c:2296
> >> #3 0x00000000007b7cae in qio_channel_rdma_close (ioc=0x3bfcc30,
> >> errp=0x0) at migration/rdma.c:2999
> >> #4 0x00000000008db60e in qio_channel_close (ioc=0x3bfcc30, errp=0x0)
> >> at io/channel.c:273
> >> #5 0x00000000007a8765 in channel_close (opaque=0x3bfcc30) at
> >> migration/qemu-file-channel.c:98
> >> #6 0x00000000007a71f9 in qemu_fclose (f=0x527c000) at
> >> migration/qemu-file.c:334
> >> #7 0x0000000000795b96 in migrate_fd_cleanup (opaque=0x3b46280) at
> >> migration/migration.c:1162
> >> #8 0x000000000093a71b in aio_bh_call (bh=0x3db7a20) at util/async.c:90
> >> #9 0x000000000093a7b2 in aio_bh_poll (ctx=0x3b121c0) at
> >> util/async.c:118
> >> #10 0x000000000093f2ad in aio_dispatch (ctx=0x3b121c0) at
> >> util/aio-posix.c:436
> >> #11 0x000000000093ab41 in aio_ctx_dispatch (source=0x3b121c0,
> >> callback=0x0, user_data=0x0)
> >> at util/async.c:261
> >> #12 0x00007f249f73c7aa in g_main_context_dispatch () from
> >> /lib64/libglib-2.0.so.0
> >> #13 0x000000000093dc5e in glib_pollfds_poll () at util/main-loop.c:215
> >> #14 0x000000000093dd4e in os_host_main_loop_wait (timeout=28000000) at
> >> util/main-loop.c:263
> >> #15 0x000000000093de05 in main_loop_wait (nonblocking=0) at
> >> util/main-loop.c:522
> >> #16 0x00000000005bc6a5 in main_loop () at vl.c:1944
> >> #17 0x00000000005c39b5 in main (argc=56, argv=0x7ffe2f6443f8,
> >> envp=0x3ad0030) at vl.c:4752
> >>
> >> It does not get the RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect
> >> sometime.
> >> I do not find out the root cause why not get RDMA_CM_EVENT_DISCONNECTED
> >> event, but
> >> it can be reproduced if not invoke ibv_dereg_mr to release all ram blocks
> >> which fixed
> >> in previous patch.
> >
> > Does this happen without your other changes?
>
> Yes, this issue also happen on v2.12.0. base on
> commit 4743c23509a51bd4ee85cc272287a41917d1be35
>
> > Can you give me instructions to repeat it and also say which
> > cards you wereusing?
>
> This issue can be reproduced by start and cancel migration.
> less than 10 times, this issue will be reproduced.
>
> The command line is:
> virsh migrate --live --copy-storage-all --undefinesource --persistent
> --timeout 10800 \
> --verbose 83e0049e-1325-4f31-baf9-25231509ada1 \
> qemu+ssh://9.16.46.142/system rdma://9.16.46.142
>
> The net card i use is :
> 0000:3b:00.0 Ethernet controller: Mellanox Technologies MT27710 Family
> [ConnectX-4 Lx]
> 0000:3b:00.1 Ethernet controller: Mellanox Technologies MT27710 Family
> [ConnectX-4 Lx]
>
> This issue is related to ibv_dereg_mr, if not invoke ibv_dereg_mr for
> all ram block, this issue can be reproduced.
> If we fixed the bugs and use ibv_dereg_mr to release all ram block,
> this issue never happens.
Maybe that is the right fix; I can imagine that the RDMA code doesn't
like closing down if there are still ramblocks registered that
potentially could have incoming DMA?
> And for the kernel part, there is a bug also cause not release ram
> block when canceling live migration.
> https://patchwork.kernel.org/patch/10385781/
OK, that's a pain; which threads are doing the dereg - is some stuff
in the migration thread and some stuff in the main thread on cleanup?
Dave
> >
> >> Anyway, it should not invoke rdma_get_cm_event in main thread, and the
> >> event channel
> >> is also destroyed in qemu_rdma_cleanup.
> >>
> >> Signed-off-by: Lidong Chen <address@hidden>
> >> ---
> >> migration/rdma.c | 12 ++----------
> >> migration/trace-events | 1 -
> >> 2 files changed, 2 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/migration/rdma.c b/migration/rdma.c
> >> index 0dd4033..92e4d30 100644
> >> --- a/migration/rdma.c
> >> +++ b/migration/rdma.c
> >> @@ -2275,8 +2275,7 @@ static int qemu_rdma_write(QEMUFile *f, RDMAContext
> >> *rdma,
> >>
> >> static void qemu_rdma_cleanup(RDMAContext *rdma)
> >> {
> >> - struct rdma_cm_event *cm_event;
> >> - int ret, idx;
> >> + int idx;
> >>
> >> if (rdma->cm_id && rdma->connected) {
> >> if ((rdma->error_state ||
> >> @@ -2290,14 +2289,7 @@ static void qemu_rdma_cleanup(RDMAContext *rdma)
> >> qemu_rdma_post_send_control(rdma, NULL, &head);
> >> }
> >>
> >> - ret = rdma_disconnect(rdma->cm_id);
> >> - if (!ret) {
> >> - trace_qemu_rdma_cleanup_waiting_for_disconnect();
> >> - ret = rdma_get_cm_event(rdma->channel, &cm_event);
> >> - if (!ret) {
> >> - rdma_ack_cm_event(cm_event);
> >> - }
> >> - }
> >> + rdma_disconnect(rdma->cm_id);
> >
> > I'm worried whether this change could break stuff:
> > The docs say for rdma_disconnect that it flushes any posted work
> > requests to the completion queue; so unless we wait for the event
> > do we know the stuff has been flushed? In the normal non-cancel case
> > I'm worried that means we could lose something.
> > (But I don't know the rdma/infiniband specs well enough to know if it's
> > really a problem).
>
> In qemu_fclose function, it invoke qemu_fflush(f) before invoke f->ops->close.
> so I think it's safe for normal migration case.
>
> For the root cause why not receive RDMA_CM_EVENT_DISCONNECTED event
> after rdma_disconnect,
> I loop in Aviad Yehezkel<address@hidden>, Aviad will help us
> find the root cause.
>
> >
> > Dave
> >
> >> trace_qemu_rdma_cleanup_disconnect();
> >> rdma->connected = false;
> >> }
> >> diff --git a/migration/trace-events b/migration/trace-events
> >> index d6be74b..64573ff 100644
> >> --- a/migration/trace-events
> >> +++ b/migration/trace-events
> >> @@ -125,7 +125,6 @@ qemu_rdma_accept_pin_state(bool pin) "%d"
> >> qemu_rdma_accept_pin_verbsc(void *verbs) "Verbs context after listen: %p"
> >> qemu_rdma_block_for_wrid_miss(const char *wcompstr, int wcomp, const char
> >> *gcompstr, uint64_t req) "A Wanted wrid %s (%d) but got %s (%" PRIu64 ")"
> >> qemu_rdma_cleanup_disconnect(void) ""
> >> -qemu_rdma_cleanup_waiting_for_disconnect(void) ""
> >> qemu_rdma_close(void) ""
> >> qemu_rdma_connect_pin_all_requested(void) ""
> >> qemu_rdma_connect_pin_all_outcome(bool pin) "%d"
> >> --
> >> 1.8.3.1
> >>
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH 1/2] migration: update index field when delete or qsort RDMALocalBlock, Lidong Chen, 2018/05/06
- [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Lidong Chen, 2018/05/06
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Dr. David Alan Gilbert, 2018/05/08
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/08
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/14
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Dr. David Alan Gilbert, 2018/05/14
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/16
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Dr. David Alan Gilbert, 2018/05/16
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/16
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Dr. David Alan Gilbert, 2018/05/16
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/16
- Re: [Qemu-devel] [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Dr. David Alan Gilbert, 2018/05/16
- Message not available
- Message not available
- Message not available
- Re: [Qemu-devel] FW: [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, Aviad Yehezkel, 2018/05/17
- Re: [Qemu-devel] FW: [PATCH 2/2] migration: not wait RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect, 858585 jemmy, 2018/05/17