[torqueusers] Slow X11-Forwarding through qsub

[Frank Mietke]

Hi there,

we're using Torque 2.1.8 in conjunction with Maui. We tried the X11-Forwarding
option of qsub to start an X application on an interactive node. But if we do
that and try to start xterm then it takes about a minute until the window is
visible. If we connect to the node through ssh directly and start xterm then it 
is visible in a second.

The strace command revealed that the read from the x-socket is the reason for the slowdown:

[snip]

mmap(NULL, 790528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2a9a196000
read(3, "\0\0\5\0\6\0\t\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 786432) = 780
read(3, 0x2a9a19631c, 785652)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\5\0\6\0\t\0\0\0\0\0\0\0\5\0\6\0\t\0\0\0\0\0\0\0\5"..., 785652) = 17408
read(3, 0x2a9a19a71c, 768244)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 768244) = 17152
read(3, 0x2a9a19ea1c, 751092)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 751092) = 17408
read(3, 0x2a9a1a2e1c, 733684)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 733684) = 17408
read(3, 0x2a9a1a721c, 716276)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\6\0\t\0\0\0\0\0\0\0\5\0\6\0\t\0\0\0\0\0\0\0\5\0\6\0\t"..., 716276) = 15616
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 700660) = 1024
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 699636) = 1024
read(3, 0x2a9a1ab71c, 698612)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 698612) = 1024
read(3, 0x2a9a1abb1c, 697588)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 697588) =  1024
read(3, 0x2a9a1abf1c, 696564)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 696564) = 1024
read(3, 0x2a9a1ac31c, 695540)           = -1 EAGAIN (Resource temporarily unavailable)

[snip]

The strace output of the ssh-connection at the same position is:

[snip]

mmap(NULL, 790528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2a9a196000
read(3, "\0\0\5\0\6\0\t\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 786432) = 16140
read(3, 0x2a9a199f1c, 770292)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\5\0\6\0\t\0\0\0\0\0\0\0\5\0\6\0\t\0\1\0\0\0\0\0\5"..., 770292) = 16384
read(3, 0x2a9a19df1c, 753908)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 753908) = 16384
read(3, 0x2a9a1a1f1c, 737524)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 737524) = 12908
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 724616) = 3476
read(3, 0x2a9a1a5f1c, 721140)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 721140) = 16384
read(3, 0x2a9a1a9f1c, 704756)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 704756) = 16384
read(3, 0x2a9a1adf1c, 688372)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\0\0\0\0\5\0\6\0\t\0\0\0\0\0\0\0\5\0\6\0\n\0\371\377"..., 688372) = 16384
read(3, 0x2a9a1b1f1c, 671988)           = -1 EAGAIN (Resource temporarily unavailable)
select(4, [3], NULL, NULL, NULL)        = 1 (in [3])
read(3, "\0\0\6\0\6\0\v\0\2\0\0\0\0\0\6\0\6\0\v\0\2\0\0\0\0\0\6"..., 671988) = 16384
read(3, 0x2a9a1b5f1c, 655604)           = -1 EAGAIN (Resource temporarily unavailable)

[snip]

Any help/hint is appreciated.

Best Regards,
Frank



-- 
Dipl.-Inf. Frank Mietke     |     Fakultätsrechen- und Informationszentrum
Tel.: 0371 - 531 - 35538    |     Fak. für Informatik
Fax:  0371 - 531 8 35538    |     TU-Chemnitz
Key-ID: 60F59599            |     frank.mietke at informatik.tu-chemnitz.de