[Mesa-dev] XSync/XReply take too much CPU

[yanhua]

Hi, Tapani:
      Recently I come into a problem. I have a opengl program, if the program run, it can take up almost one core, and the Xorg takes almost one core too.
      I found this program continuously recvmsg from the Xorg. I'm sure the CPU is takeing by too much sendmsg/recvmsg. 

 Following is the backtrace of this program when it call recvmsg:




#0  recvmsg () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007fb88abffdd7 in _xcb_in_read (c=c at entry=0x277e990) at ../../src/xcb_in.c:982
#2  0x00007fb88abfded1 in _xcb_conn_wait (c=c at entry=0x277e990, cond=cond at entry=0x7fb8667fa5c0, vector=vector at entry=0x0, 
    count=count at entry=0x0) at ../../src/xcb_conn.c:495
#3  0x00007fb88abff617 in wait_for_reply (c=c at entry=0x277e990, request=2575173, e=e at entry=0x7fb8667fa690)
    at ../../src/xcb_in.c:516
#4  0x00007fb88abff721 in xcb_wait_for_reply (c=0x277e990, request=2575173, e=0x7fb8667fa690) at ../../src/xcb_in.c:546
#5  0x00007fb88dd64ae7 in _XReply () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#6  0x00007fb88dd6052d in XSync () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#7  0x00007fb88748c1de in dri2XcbSwapBuffers (pdraw=0x7fb849a058c0, remainder=<optimized out>, divisor=0, target_msc=0, 
    dpy=0x277d6d0) at dri2_glx.c:815


I strace the program's syscall, 

the data is almost zeros. 

recvmsg(20, {msg_name(0)=NULL, msg_iov(1)=[{"g\0\325R\v\0@\4\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 2048



Could you tell me what's the possible cause  of this problem.


---------------------------

Yanhua
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