Re: [Xen-devel] [PATCH v3 00/18] libxl: domain save/restore: run in a separate process

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-06-08 at 18:34 +0100, Ian Jackson wrote:
> This is v3 of my series to asyncify save/restore, rebased to current
> tip, retested, and with all comments addressed.

There's quite a lot of combinations which need testing here (PV, HVM,
HVM w/ stub dm, old vs new qemu etc etc), which of those have you tried?

I tried a simple localhost migrate of a PV guest and:
        # xl -vvv migrate d32-1 localhost
        migration target: Ready to receive domain.
        Saving to migration stream new xl format (info 0x0/0x0/3541)
        libxl: debug: libxl.c:722:libxl_domain_suspend: ao 0x8069720: create: 
how=(nil) callback=(nil) poller=0x80696c8
        Loading new save file <incoming migration stream> (new xl fmt info 
0x0/0x0/3541)
         Savefile contains xl domain config
        libxl: debug: libxl_dom.c:969:libxl__toolstack_save: domain=2 toolstack 
data size=8
        libxl: debug: libxl.c:745:libxl_domain_suspend: ao 0x8069720: 
inprogress: poller=0x80696c8, flags=i
        libxl-save-helper: debug: starting save: Success
        xc: detail: Had 0 unexplained entries in p2m table
        xc: Saving memory: iter 0 (last sent 0 skipped 0): 0/131072    0%
        
at which point it appears to just stop.

        # strace -p 2872 # /usr/lib/xen/bin/libxl-save-helper --save-domain 8 2 
0 0 1 0 0 12 8 72
        Process 2872 attached - interrupt to quit
        write(8, 0xb5d31000, 1974272^C <unfinished ...>
        Process 2872 detached
        # strace -p 2866 # /usr/lib/xen/bin/libxl-save-helper --restore-domain 
0 3 1 0 2 0 0 1 0 0 0
        Process 2866 attached - interrupt to quit
        read(0, ^C <unfinished ...>
        # strace -p 4070 # xl -vvv migrate d32-1 localhost
        Process 4070 attached - interrupt to quit
        restart_syscall(<... resuming interrupted call ...>
        # strace -p 4074 # xl migrate-receive
        Process 4074 attached - interrupt to quit
        restart_syscall(<... resuming interrupted call ...>

So the saver seems to be blocked writing to fd 8, which is argv[1] == io_fd.

Also FWIW:
        # xl list
        Name                                        ID   Mem VCPUs      State   
Time(s)
        Domain-0                                     0   511     4     r-----   
   24.5
        d32-1                                        2   128     4     -b----   
    0.4
        d32-1--incoming                              3     0     0     --p---   
    0.0

/var/log/xen/xl-d32-1.log is just "Waiting for domain d32-1 (domid 9) to
die [pid 4045]" (nb: this was a newer attempt than the ones above, to be
sure I was looking at the right log, so the domid's don't match, 9 ==
d32-1 not the incoming one). There is no xl log for the incoming domain.

Also it'd be worth pinging/CCing Shriram next time to get him to sanity
test the Remus cases too.

I'm in the middle of reviewing #5/19 (the meat), I'll keep going
although I doubt I'll spot the cause of this...

Ian.



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