I don't understand. What would adding runtime.Goscheduled() do here? I don't
have any explicit loops in this service.
On Jul 1, 2019, 9:11 PM -0400, Michael Jones <michael.jo...@gmail.com>, wrote:
> Does adding runtime.GoSched() calls make any difference?
>
> > On Mon, Jul 1, 2019 at 5:37 PM 'Yunchi Luo' via golang-nuts
> > <golang-nuts@googlegroups.com> wrote:
> > > Following that logic, a leak of TCP connections should manifest as a file
> > > descriptor leak. We have the process_open_fds metric from Prometheus,
> > > that is the number of open file descriptors as found in /proc/<pid>/fd.
> > > The number of descriptors overtime correlates well with the amount of
> > > traffic, pretty cyclic. There doesn't appear to be a leak.
> > >
> > > We don't do our own memory management and the binary is compiled with
> > > CGO_ENABLED=0.
> > >
> > > I still think the issue I'm seeing should be GC (or heap) related, given
> > > the explosion in mark & sweep time, HeapSys, HeapIdle, and HeapReleased
> > > just before the process dies. But I'm lacking ideas on how to track down
> > > the cause of the increase.
> > >
> > > > On Mon, Jul 1, 2019 at 5:39 PM Robert Engels <reng...@ix.netcom.com>
> > > > wrote:
> > > > > I think don't think you are going to find it in the 'heap', rather it
> > > > > would be in native memory.
> > > > >
> > > > > I would use the monitor the /proc/[pid] for the process, and pay
> > > > > attention to the 'fd','net' and 'statm' - if my theory is correct you
> > > > > will see growth here long before the process is killed. Since you are
> > > > > running under k8s and cgroups, you will need to do this along side
> > > > > the Go process (unless you have root access to the server).
> > > > >
> > > > > I 'think' depending on kernel version, that kernel memory used goes
> > > > > against the process for OOM purposes, so this is a likely candidate
> > > > > if pprof is showing nothing.
> > > > >
> > > > > Do you by chance do any of your own memory management (via
> > > > > malloc/CGO)? If so, this is not going to show in pprof either.
> > > > > > -----Original Message-----
> > > > > > From: 'Yunchi Luo' via golang-nuts
> > > > > > Sent: Jul 1, 2019 4:26 PM
> > > > > > To: Robert Engels
> > > > > > Cc: golang-nuts@googlegroups.com, Alec Thomas
> > > > > > Subject: Re: [go-nuts] OOM occurring with a small heap
> > > > > >
> > > > > > I actually have a heap profile (pasted at the bottom) from about 1
> > > > > > second before the service died (the goroutine that is logging
> > > > > > "[Memory]" triggers heap profiles once RSS > 100MB). I don't see
> > > > > > TCP connections there. Maybe it's too few to be sampled. How would
> > > > > > I verify your theory? That the service dies within 2 seconds after
> > > > > > several hours makes it very hard to debug.
> > > > > >
> > > > > > The top thing in the heap profile is from the reflect package. I
> > > > > > initially found that suspect, but it turns out this comes from a
> > > > > > use of httptrace.ClientTrace I had for counting new connections to
> > > > > > DynamoDB.
> > > > > >
> > > > > > tracer := &httptrace.ClientTrace{
> > > > > > ConnectStart: func(_, _ string) {
> > > > > > newConns.Inc()
> > > > > > },
> > > > > > }
> > > > > >
> > > > > > `newConns` is just a prometheus counter. The `tracer` object itself
> > > > > > is created once and re-used with every client request context. On
> > > > > > request, `httptrace.WithClientTrace(ctx, tracer)` uses reflection
> > > > > > to compose the trace functions under-the-hood and uses reflection
> > > > > > to invoke it, hence the reflect.funcLayout and reflect.Value.call.
> > > > > > Objects in `reflect` account for about 50% of heap in terms of
> > > > > > size, and does seem to grow as the service is running out of
> > > > > > memory, but that's only 12MB so I thought it was a red herring.
> > > > > >
> > > > > > Heap profile:
> > > > > > Type: inuse_space
> > > > > > Time: Jun 30, 2019 at 4:46am (EDT)
> > > > > > Entering interactive mode (type "help" for commands, "o" for
> > > > > > options)
> > > > > > (pprof) inuse_objects
> > > > > > (pprof) top
> > > > > > Showing nodes accounting for 414485, 100% of 414485 total
> > > > > > Showing top 10 nodes out of 81
> > > > > > flat flat% sum% cum cum%
> > > > > > 344074 83.01% 83.01% 344074 83.01% reflect.funcLayout.func1
> > > > > > 32768 7.91% 90.92% 376842 90.92% reflect.callReflect
> > > > > > 16384 3.95% 94.87% 16384 3.95%
> > > > > > github.com/json-iterator/go.processTags
> > > > > > 10923 2.64% 97.51% 10923 2.64% context.WithValue
> > > > > > 8192 1.98% 99.48% 8192 1.98% crypto/hmac.New
> > > > > > 1260 0.3% 99.79% 1260 0.3%
> > > > > > github.com/aws/aws-sdk-go/aws/signer/v4.(*signingCtx).buildCanonicalHeaders
> > > > > > 820 0.2% 100% 820 0.2%
> > > > > > github.com/stripe/veneur/tdigest.NewMerging
> > > > > > 64 0.015% 100% 64 0.015% reflect.addReflectOff
> > > > > > 0 0% 100% 820 0.2%
> > > > > > git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).Observe
> > > > > > 0 0% 100% 820 0.2%
> > > > > > git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).openDigests
> > > > > > (pprof) cum
> > > > > > (pprof) top
> > > > > > Showing nodes accounting for 376842, 90.92% of 414485 total
> > > > > > Showing top 10 nodes out of 81
> > > > > > flat flat% sum% cum cum%
> > > > > > 0 0% 0% 376842 90.92%
> > > > > > net/http/httptrace.(*ClientTrace).compose.func1
> > > > > > 0 0% 0% 376842 90.92% reflect.Value.Call
> > > > > > 0 0% 0% 376842 90.92% reflect.Value.call
> > > > > > 32768 7.91% 7.91% 376842 90.92% reflect.callReflect
> > > > > > 0 0% 7.91% 376842 90.92% reflect.makeFuncStub
> > > > > > 344074 83.01% 90.92% 344074 83.01% reflect.funcLayout.func1
> > > > > > 0 0% 90.92% 344074 83.01% sync.(*Pool).Get
> > > > > > 0 0% 90.92% 16448 3.97%
> > > > > > github.com/json-iterator/go._createDecoderOfType
> > > > > > 0 0% 90.92% 16448 3.97%
> > > > > > github.com/json-iterator/go.createDecoderOfType
> > > > > > 0 0% 90.92% 16448 3.97%
> > > > > > github.com/json-iterator/go.decoderOfStruct
> > > > > >
> > > > > >
> > > > > > > On Mon, Jul 1, 2019 at 4:32 PM Robert Engels
> > > > > > > <reng...@ix.netcom.com> wrote:
> > > > > > > >
> > > > > > > > A leak of the TCP connections (maybe not properly closed)? Each
> > > > > > > > TCP connection will use kernel memory and process memory (local
> > > > > > > > buffers), that won't be on the heap (the reference to the TCP
> > > > > > > > connection will be in the Go heap, but is probably much smaller
> > > > > > > > than the buffer allocation).
> > > > > > > >
> > > > > > > > That would be my guess - but just a guess.
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: 'Yunchi Luo' via golang-nuts
> > > > > > > > > Sent: Jul 1, 2019 2:14 PM
> > > > > > > > > To: golang-nuts@googlegroups.com
> > > > > > > > > Cc: Alec Thomas
> > > > > > > > > Subject: [go-nuts] OOM occurring with a small heap
> > > > > > > > >
> > > > > > > > > Hello, I'd like to solicit some help with a weird GC issue we
> > > > > > > > > are seeing.
> > > > > > > > >
> > > > > > > > > I'm trying to debug OOM on a service we are running in k8s.
> > > > > > > > > The service is just a CRUD server hitting a database
> > > > > > > > > (DynamoDB). Each replica serves about 300 qps of traffic.
> > > > > > > > > There are no memory leaks. On occasion (seemingly correlated
> > > > > > > > > to small latency spikes on the backend), the service would
> > > > > > > > > OOM. This is surprising because it has a circuit breaker that
> > > > > > > > > drops requests after 200 concurrent connections that has
> > > > > > > > > never trips, and goroutine profiles confirm that there are
> > > > > > > > > nowhere 200 active goroutines.
> > > > > > > > >
> > > > > > > > > GC logs are pasted below. It's interlaced with dumps of
> > > > > > > > > runtime.Memstats (the RSS number is coming from
> > > > > > > > > /proc/<pid>/stats). Go version is 1.12.5, running an Alpine
> > > > > > > > > 3.10 container in an Amazon kernel
> > > > > > > > > 4.14.123-111.109.amzn2.x86_64.
> > > > > > > > >
> > > > > > > > > The service happily serves requests using ~50MB of RSS for
> > > > > > > > > hours, until the last 2 seconds, where GC mark&sweep time
> > > > > > > > > starts to 2-4X per cycle (43+489/158/0.60+0.021 ms cpu =>
> > > > > > > > > 43+489/158/0.60+0.021 ms cpu), and RSS and Sys blow up. It’s
> > > > > > > > > also interesting that in the last log line: `Sys=995MB
> > > > > > > > > RSS=861MB HeapSys=199MB`. If I’m reading this correctly,
> > > > > > > > > there’s at least `662MB` of memory in RSS that is not
> > > > > > > > > assigned to the heap. Though this might be due to the change
> > > > > > > > > in 1.125 to use MADV_FREE, so the pages are freeable not yet
> > > > > > > > > reclaimed by the kernel.
> > > > > > > > >
> > > > > > > > > I don’t understand how heap can be so small across gc cycles
> > > > > > > > > (28->42->30MB on the last line means heap doesn't grow past
> > > > > > > > > 42MB?), yet RSS keeps growing. I'm assuming the increased RSS
> > > > > > > > > is causing the kernel to OOM the service, but that should
> > > > > > > > > only happen if the RSS is not freeable as marked by
> > > > > > > > > MADV_FREE. There doesn't seem to be any indication of that
> > > > > > > > > from the GC logs. I guess this all comes down to me not
> > > > > > > > > having a good understanding of how the GC algorithm works and
> > > > > > > > > how to read these logs. I'd really appreciate it if anyone
> > > > > > > > > can explain what's happening and why.
> > > > > > > > >
> > > > > > > > > gc 41833 @19135.227s 0%: 0.019+2.3+0.005 ms clock,
> > > > > > > > > 0.079+0.29/2.2/5.6+0.020 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:04.886 [Memory]: Alloc=7MB
> > > > > > > > > TotalAlloc=230172MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=51MB HeapInUse=11MB HeapReleased=5MB
> > > > > > > > > gc 41834 @19135.869s 0%: 0.005+2.9+0.003 ms clock,
> > > > > > > > > 0.023+0.32/2.5/6.6+0.012 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:05.886 [Memory]: Alloc=9MB
> > > > > > > > > TotalAlloc=230179MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=50MB HeapInUse=12MB HeapReleased=5MB
> > > > > > > > > gc 41835 @19136.704s 0%: 0.038+2.1+0.004 ms clock,
> > > > > > > > > 0.15+0.35/2.1/5.3+0.016 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:06.886 [Memory]: Alloc=9MB
> > > > > > > > > TotalAlloc=230184MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=50MB HeapInUse=12MB HeapReleased=5MB
> > > > > > > > > gc 41836 @19137.611s 0%: 0.009+2.1+0.003 ms clock,
> > > > > > > > > 0.036+0.39/2.0/5.7+0.015 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:07.887 [Memory]: Alloc=10MB
> > > > > > > > > TotalAlloc=230190MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=49MB HeapInUse=12MB HeapReleased=5MB
> > > > > > > > > gc 41837 @19138.444s 0%: 0.008+2.1+0.004 ms clock,
> > > > > > > > > 0.035+0.51/2.1/5.7+0.017 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:08.887 [Memory]: Alloc=10MB
> > > > > > > > > TotalAlloc=230195MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=49MB HeapInUse=12MB HeapReleased=5MB
> > > > > > > > > gc 41838 @19139.474s 0%: 0.005+2.6+0.003 ms clock,
> > > > > > > > > 0.023+0.37/2.5/4.3+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > gc 41839 @19140.173s 0%: 0.011+2.4+0.003 ms clock,
> > > > > > > > > 0.046+0.20/2.3/5.8+0.015 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:09.887 [Memory]: Alloc=7MB
> > > > > > > > > TotalAlloc=230202MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=50MB HeapInUse=11MB HeapReleased=5MB
> > > > > > > > > gc 41840 @19140.831s 0%: 0.082+2.1+0.003 ms clock,
> > > > > > > > > 0.32+0.64/2.1/5.3+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:10.887 [Memory]: Alloc=9MB
> > > > > > > > > TotalAlloc=230209MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=50MB HeapInUse=12MB HeapReleased=5MB
> > > > > > > > > gc 41841 @19141.655s 0%: 0.014+2.1+0.003 ms clock,
> > > > > > > > > 0.056+0.28/2.0/5.7+0.013 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > gc 41842 @19142.316s 0%: 0.006+2.7+0.003 ms clock,
> > > > > > > > > 0.027+0.29/2.6/6.2+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:11.888 [Memory]: Alloc=6MB
> > > > > > > > > TotalAlloc=230216MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=51MB HeapInUse=11MB HeapReleased=5MB
> > > > > > > > > gc 41843 @19142.942s 0%: 0.010+2.1+0.005 ms clock,
> > > > > > > > > 0.040+0.29/2.0/5.7+0.023 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:12.888 [Memory]: Alloc=9MB
> > > > > > > > > TotalAlloc=230223MB Sys=69MB RSS=51MB HeapSys=62MB
> > > > > > > > > HeapIdle=50MB HeapInUse=11MB HeapReleased=5MB
> > > > > > > > > gc 41844 @19143.724s 0%: 0.008+2.4+0.004 ms clock,
> > > > > > > > > 0.035+0.38/2.0/5.7+0.017 ms cpu, 11->11->5 MB, 12 MB goal, 4 P
> > > > > > > > > gc 41845 @19144.380s 0%: 10+9.3+0.044 ms clock,
> > > > > > > > > 43+6.1/9.2/4.4+0.17 ms cpu, 11->11->6 MB, 12 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:13.901 [Memory]: Alloc=6MB
> > > > > > > > > TotalAlloc=230230MB Sys=136MB RSS=98MB HeapSys=94MB
> > > > > > > > > HeapIdle=83MB HeapInUse=11MB HeapReleased=35MB
> > > > > > > > > gc 41846 @19144.447s 0%: 0.008+26+0.005 ms clock,
> > > > > > > > > 0.033+0.46/7.8/26+0.020 ms cpu, 11->12->9 MB, 12 MB goal, 4 P
> > > > > > > > > gc 41847 @19144.672s 0%: 0.013+76+0.006 ms clock,
> > > > > > > > > 0.053+0.20/6.4/80+0.024 ms cpu, 17->18->8 MB, 18 MB goal, 4 P
> > > > > > > > > gc 41848 @19145.014s 0%: 0.008+172+0.005 ms clock,
> > > > > > > > > 0.035+0.13/8.5/177+0.022 ms cpu, 15->17->10 MB, 16 MB goal, 4
> > > > > > > > > P
> > > > > > > > > gc 41849 @19145.298s 0%: 0.007+285+0.006 ms clock,
> > > > > > > > > 0.030+10/285/7.6+0.024 ms cpu, 19->23->15 MB, 20 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:15.052 [Memory]: Alloc=22MB
> > > > > > > > > TotalAlloc=230264MB Sys=598MB RSS=531MB HeapSys=265MB
> > > > > > > > > HeapIdle=240MB HeapInUse=25MB HeapReleased=164MB
> > > > > > > > > gc 41850 @19145.665s 0%: 10+419+0.005 ms clock,
> > > > > > > > > 43+489/158/0.60+0.021 ms cpu, 26->30->17 MB, 30 MB goal, 4 P
> > > > > > > > > gc 41851 @19146.325s 0%: 21+798+0.036 ms clock,
> > > > > > > > > 86+990/401/0+0.14 ms cpu, 28->42->30 MB, 34 MB goal, 4 P
> > > > > > > > > INFO 2019-06-30T08:46:16.613 [Memory]: Alloc=41MB
> > > > > > > > > TotalAlloc=230303MB Sys=995MB RSS=861MB HeapSys=199MB
> > > > > > > > > HeapIdle=155MB HeapInUse=44MB HeapReleased=54MB
> > > > > > > > >
> > > > > > > > > I also captured the OOM log from dmesg here
> > > > > > > > > https://gist.github.com/mightyguava/7ecc6fc55f5cd925062d6beede3783b3.
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > Yunchi
> > > > > > > > > --
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