Re: kern/50313: processes get stuck doing exec

[Havard Eidnes <he%uninett.no@localhost>]

The following reply was made to PR kern/50313; it has been noted by GNATS.

From: Havard Eidnes <he%uninett.no@localhost>
To: gnats-bugs%NetBSD.org@localhost, dholland-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
 netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/50313: processes get stuck doing exec
Date: Sun, 11 Oct 2015 01:20:39 +0200 (CEST)

 >   > Memory resource pool statistics
 >   > Name        Size Requests Fail Releases Pgreq Pgrel Npage Hiwat M=
 inpg Maxpg Idle
 >   > ...
 >   > execargs    262144  40498    0    40498     9     7     2     4  =
    0    16    2
 >   > ...
 >
 >  Out of curiosity: how much RAM is in the system?
 
 Physically 4G, but since this is i386, my kernel sees
 
 total memory =3D 3316 MB
 avail memory =3D 3248 MB
 
 >  Because exec args are big, unless there's a throttle (I don't
 >  think we have one) it's fairly easy for transient demand to
 >  take up a lot of space, which can fill up the kernel map or
 >  plain run out of memory.
 
 Do we have a meter for the kernel map, inspectable from user-land
 in some way?
 
 When this problem strikes, it's usually going downhill.
 Presently my host has a load average of 10, mostly caused by:
 
   PID TTY    STAT      TIME COMMAND
 ...
  1311 ?      D      0:00.00 cron: running job =
 
  2828 ?      Rs     0:00.00 (local)
  3101 ?      RVs    0:00.00 (cron)
  5471 ?      D      0:00.00 cron: running job =
 
  7074 ?      D      0:00.00 cron: running job =
 
 23096 ?      RVs    0:00.00 (cron)
 23277 ?      RVs    0:00.00 (cron)
 23347 ?      RVs    0:00.00 (cron)
 25722 ?      RVs    0:00.00 (cron)
 26808 ?      D      0:00.00 cron: running job =
 
 29057 ?      R      0:00.00 (sh)
 
 and some mail delivery appears to get stuck:
 
 Oct 11 01:17:03 smistad postfix/qmgr[14168]: D81A13D0B8: skipped, still=
  being delivered
 
 Some of these are stuck doing uvm_km_alloc(), some of them stuck
 in fork:
 
 crash> t/t 0t5471
 trace: pid 5471 lid 1 at 0xdd07ebe4
 sleepq_block(0,0,c0be3a51,c0cda590,8,c4677c00,c4675280,c9002034,0,cf7fa=
 dfc) at sleepq_block+0xa3
 cv_wait(cf7fadfc,c4614f00,ddbb3000,80000000,0,0,c0803314,c8c2ad40,dd07e=
 c88,0) at cv_wait+0x126
 fork1(c4c90560,3,14,0,0,c0803314,0,dd07ed28,0,dd07ed3c) at fork1+0x6a0
 sys___vfork14(c4c90560,dd07ed00,dd07ed28,c0803389,c77357ac,11a,bbab9000=
 ,bbab9d30,c77357ac,cf7fade4) at sys___vfork14+0x50
 syscall(dd07ed48,bbbb00b3,ab,bfbf001f,bbba001f,1c20,0,bfbfed98,0,bb91e1=
 53) at syscall+0xaa
 crash> =
 
 
 Regards,
 
 - H=E5vard