[Bug 1565978] Re: ISST-LTE:pVM: golang does not support huge amount (>256) CPUs machines (as E870)

[Breno Leitão]

I am going to ask to send the following patch upstream. Let see what the
upstream community will say about it

commit 17857791d91cf31944d266cb1dfd9322cea8933f
Author: Breno Leitao <breno.leitao at gmail.com>
Date:   Mon Apr 4 16:09:55 2016 -0400

    Increase _MaxGomaxprocs to support big machines
    
    Currently go does not support machines that contains > 256 CPUs, as IBM's E880
    that could host 1536 hardware thread, when configured with 192 CPU cores and
    SMT (Symmetric Multi Thread) 8.
    
    For example, when running a go program on this machine, I got, the following
    problem[1]:
    
      procresize: invalid arg
    
    This is because of the following code:
    
      _MaxGomaxprocs = 1 << 8
    
      if old < 0 || old > _MaxGomaxprocs || nprocs <= 0 || nprocs > _MaxGomaxprocs {
          throw("procresize: invalid arg")
      }
    
    This patch just redefine _MAxGomaxprocs to 1 << 12.

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index e0137f7..508cecb 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -472,7 +472,7 @@ type p struct {
 const (
 	// The max value of GOMAXPROCS.
 	// There are no fundamental restrictions on the value.
-	_MaxGomaxprocs = 1 << 8
+	_MaxGomaxprocs = 1 << 12
 )
 
 type schedt struct {

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https://bugs.launchpad.net/bugs/1565978

Title:
  ISST-LTE:pVM: golang does not support huge amount (>256)  CPUs
  machines (as E870)

Status in golang-1.6 package in Ubuntu:
  New

Bug description:
  Docker and golang packages are not able to run on e870 machine due to
  a lot of CPU on these machines.

  The current machine has 400 CPUs and shows the following error:

  runtime stack:
  runtime.throw(0x654c60, 0x17)
          /usr/lib/go/src/runtime/panic.go:530 +0x8c
  runtime.procresize(0x190, 0x0)
          /usr/lib/go/src/runtime/proc.go:3158 +0xbd4
  runtime.schedinit()
          /usr/lib/go/src/runtime/proc.go:452 +0x140
  runtime.rt0_go(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2, 0x3fffd512de59, ...)
          /usr/lib/go/src/runtime/asm_ppc64x.s:72 +0xac
  /var/lib/dpkg/info/golang-go.postinst: line 18: 100 +  : syntax error: operand expected (error token is "+  ")
  dpkg: error processing package golang-go (--configure):
   subprocess installed post-installation script returned error exit status 1
  dpkg: dependency problems prevent configuration of golang-doc:
   golang-doc depends on golang-go; however:
    Package golang-go is not configured yet.

  dpkg: error processing package golang-doc (--configure):
   dependency problems - leaving unconfigured
  dpkg: dependency problems prevent configuration of golang:
   golang depends on golang-doc (>= 2:1.6-1ubuntu1); however:
    Package golang-doc is not configured yet.
   golang depends on golang-go (>= 2:1.6-1ubuntu1); however:
    Package golang-go is not configured yet.

  dpkg: error processing package golang (--configure):
   dependency problems - leaving unconfigured
  No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                            No apport report written because the error message indicates its a followup error from a previous failure.
                                                        Errors were encountered while processing:
   golang-go
   golang-doc
   golang
  E: Sub-process /usr/bin/dpkg returned an error code (1)

  Looking at the code I see:

  _MaxGomaxprocs = 1 << 8

          if old < 0 || old > _MaxGomaxprocs || nprocs <= 0 || nprocs > _MaxGomaxprocs {
                  throw("procresize: invalid arg")
          }

  If I decrease the amount of CPU to < 256, I don't see a problem.

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