Shared Memory queuing up in xlib backend for slow X Server 1.9.5
Submitted by kas..@..ain.de
Assigned to Chris Wilson @ickle
Description
I let run the gvncviewer (from library gtk-vnc) in fullscreen mode. Under heavy load e.g. changing the complete screen content on vnc server side every 0.01 secs gvncviewer starts queueing up memory in SHM. (See bottom of the mail) Queueing up means more and more shared memory segments are allocated by cairo
The problem lies in function _cairo_xlib_shm_info_create It tries to find a empty space in current shm pool. If this not happens it simply create a new shm segment. This happens all the time so on my slow computer it accumulates approx 1 GB in 10 minutes
I assume if the X Server is too slow to get managed with a work load it blocks the shared memory segments until it is done. But the xserver is much slower than the cairo backend produces the load the shared memory is growing until out of mem.
For verification i just added a sync(display) call before searching in shm pool and the problem is gone.
Here a shortened example of pmap output of the process after running a while
08048000 20K r-xp /usr/bin/gvncviewer 0804d000 4K rw-p /usr/bin/gvncviewer 0804e000 656K rw-p [heap] 7c8e6000 196K rw-p [ anon ] 7c917000 32768K rw-s /SYSV00000000 7e917000 196K rw-p [ anon ] 7e948000 32768K rw-s /SYSV00000000 80948000 196K rw-p [ anon ] 80979000 32768K rw-s /SYSV00000000 82979000 196K rw-p [ anon ] 829aa000 32768K rw-s /SYSV00000000 849aa000 196K rw-p [ anon ] 849db000 32768K rw-s /SYSV00000000 869db000 196K rw-p [ anon ] 86a0c000 32768K rw-s /SYSV00000000 88a0c000 196K rw-p [ anon ] 88a3d000 32768K rw-s /SYSV00000000 8aa3d000 196K rw-p [ anon ] 8aa6e000 32768K rw-s /SYSV00000000 8ca6e000 196K rw-p [ anon ] 8ca9f000 32768K rw-s /SYSV00000000 8ea9f000 196K rw-p [ anon ] 8ead0000 32768K rw-s /SYSV00000000 90ad0000 196K rw-p [ anon ] 90b01000 32768K rw-s /SYSV00000000 92b01000 196K rw-p [ anon ] 92b32000 32768K rw-s /SYSV00000000 94b32000 196K rw-p [ anon ] 94b63000 32768K rw-s /SYSV00000000 96b63000 196K rw-p [ anon ] 96b94000 32768K rw-s /SYSV00000000 98b94000 196K rw-p [ anon ] 98bc5000 32768K rw-s /SYSV00000000 9abc5000 196K rw-p [ anon ] 9abf6000 32768K rw-s /SYSV00000000 9cbf6000 196K rw-p [ anon ] 9cc27000 32768K rw-s /SYSV00000000 9ec27000 196K rw-p [ anon ] 9ec58000 32768K rw-s /SYSV00000000 a0c58000 196K rw-p [ anon ] a0c89000 32768K rw-s /SYSV00000000 a2c89000 196K rw-p [ anon ] a2cba000 32768K rw-s /SYSV00000000 a4cba000 196K rw-p [ anon ] a4ceb000 32768K rw-s /SYSV00000000 a6ceb000 196K rw-p [ anon ] a6d1c000 32768K rw-s /SYSV00000000 a8d1c000 196K rw-p [ anon ] a8d4d000 32768K rw-s /SYSV00000000 aad4d000 196K rw-p [ anon ] aad7e000 32768K rw-s /SYSV00000000 acd7e000 196K rw-p [ anon ] acdaf000 32768K rw-s /SYSV00000000 aedaf000 196K rw-p [ anon ] aede0000 32768K rw-s /SYSV00000000 b0de0000 196K rw-p [ anon ] b0e11000 32768K rw-s /SYSV00000000 b2e11000 5128K rw-p [ anon ] ...... ..... .. .
Version: 1.12.16