- 24 Apr, 2015 19 commits
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Austin Clements authored
When findRunnable considers running a fractional mark worker, it first checks if there's any work to be done; if there isn't there's no point in running the worker because it will just reschedule immediately. However, currently findRunnable just checks work.full and work.partial, whereas getfull can *also* draw work from m.currentwbuf. As a result, findRunnable may not start a worker even though there actually is work. This problem manifests itself in occasional failures of the test/init1.go test. This test is unusual because it performs a large amount of allocation without executing any write barriers, which means there's nothing to force the pointers in currentwbuf out to the work.partial/full lists where findRunnable can see them. This change fixes this problem by making findRunnable also check for a currentwbuf. This aligns findRunnable with trygetfull's notion of whether or not there's work. Change-Id: Ic76d22b7b5d040bc4f58a6b5975e9217650e66c4 Reviewed-on: https://go-review.googlesource.com/9299Reviewed-by:
Russ Cox <rsc@golang.org>
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Austin Clements authored
Currently, findRunnable only considers running a mark worker if there's work in the work queue. In principle, this can delay the start of the desired number of dedicated mark workers if there's no work pending. This is unlikely to occur in practice, since there should be work queued from the scan phase, but if it were to come up, a CPU hog mutator could slow down or delay garbage collection. This check makes sense for fractional mark workers, since they'll just return to the scheduler immediately if there's no work, but we want the scheduler to start all of the dedicated mark workers promptly, even if there's currently no queued work. Hence, this change moves the pending work check after the check for starting a dedicated worker. Change-Id: I52b851cc9e41f508a0955b3f905ca80f109ea101 Reviewed-on: https://go-review.googlesource.com/9298Reviewed-by:
Rick Hudson <rlh@golang.org>
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Austin Clements authored
bgMarkCount no longer exists. Change-Id: I3aa406fdccfca659814da311229afbae55af8304 Reviewed-on: https://go-review.googlesource.com/9297Reviewed-by:
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Hyang-Ah Hana Kim authored
Instead of comparing against the entire output that may include verbose warning messages, use the last line of the output and check it includes the expected success message (PASS). Change-Id: Iafd583ee5529a8aef5439b9f1f6ce0185e4b1331 Reviewed-on: https://go-review.googlesource.com/9304Reviewed-by:
David Crawshaw <crawshaw@golang.org>
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Rob Pike authored
Also rename and update mkdoc.sh to mkalldocs.sh Change-Id: Ief3673c22d45624e173fc65ee279cea324da03b5 Reviewed-on: https://go-review.googlesource.com/9226Reviewed-by:
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Srdjan Petrovic authored
The motivation is that sysAlloc/Free() currently aren't safe to be called without a valid G, because arm's xadd64() uses locks that require a valid G. The solution here was proposed by Dmitry Vyukov: use xadduintptr() instead of xadd64(), until arm can support xadd64 on all of its architectures (not a trivial task for arm). Change-Id: I250252079357ea2e4360e1235958b1c22051498f Reviewed-on: https://go-review.googlesource.com/9002Reviewed-by:
Dmitry Vyukov <dvyukov@google.com>
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Hyang-Ah Hana Kim authored
- main3.c tests main.main is exported when compiled for GOOS=android. - wait longer for main2.c (it's slow on android/arm) - rearranged test.bash Fixes #10070. Change-Id: I6e5a98d1c5fae776afa54ecb5da633b59b269316 Reviewed-on: https://go-review.googlesource.com/9296Reviewed-by:
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Michael Hudson-Doyle authored
This lets us avoid loading string constants via the GOT and (together with http://golang.org/cl/9102) results in the fannkuch benchmark having very similar register usage with -dynlink as without. Change-Id: Ic3892b399074982b76773c3e547cfbba5dabb6f9 Reviewed-on: https://go-review.googlesource.com/9103Reviewed-by:
Ian Lance Taylor <iant@golang.org> Run-TryBot: Ian Lance Taylor <iant@golang.org>
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Austin Clements authored
Currently, when allocation reaches the GC trigger, the runtime uses readyExecute to start the GC goroutine immediately rather than wait for the scheduler to get around to the GC goroutine while the mutator continues to grow the heap. Now that the scheduler runs the most recently readied goroutine when a goroutine yields its time slice, this rigmarole is no longer necessary. The runtime can simply ready the GC goroutine and yield from the readying goroutine. Change-Id: I3b4ebadd2a72a923b1389f7598f82973dd5c8710 Reviewed-on: https://go-review.googlesource.com/9292Reviewed-by:
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Austin Clements authored
Currently, the main GC goroutine sleeps on a note during concurrent mark and the first background mark worker or assist to finish marking use wakes up that note to let the main goroutine proceed into mark termination. Unfortunately, the latency of this wakeup can be quite high, since the GC goroutine will typically have lost its P while in the futex sleep, meaning it will be placed on the global run queue and will wait there until some P is kind enough to pick it up. This delay gives the mutator more time to allocate and create floating garbage, growing the heap unnecessarily. Worse, it's likely that background marking has stopped at this point (unless GOMAXPROCS>4), so anything that's allocated and published to the heap during this window will have to be scanned during mark termination while the world is stopped. This change replaces the note sleep/wakeup with a gopark/ready scheme. This keeps the wakeup inside the Go scheduler and lets the garbage collector take advantage of the new scheduler semantics that run the ready()d goroutine immediately when the ready()ing goroutine sleeps. For the json benchmark from x/benchmarks with GOMAXPROCS=4, this reduces the delay in waking up the GC goroutine and entering mark termination once concurrent marking is done from ~100ms to typically <100µs. Change-Id: Ib11f8b581b8914f2d68e0094f121e49bac3bb384 Reviewed-on: https://go-review.googlesource.com/9291Reviewed-by:
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Austin Clements authored
Currently, we use a note sleep with a timeout in a loop in func gc to periodically revise the GC control variables. Replace this with a fully blocking note sleep and use a periodic timer to trigger the revise instead. This is a step toward replacing the note sleep in func gc. Change-Id: I2d562f6b9b2e5f0c28e9a54227e2c0f8a2603f63 Reviewed-on: https://go-review.googlesource.com/9290Reviewed-by:
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Austin Clements authored
Currently, when the runtime ready()s a G, it adds it to the end of the current P's run queue and continues running. If there are many other things in the run queue, this can result in a significant delay before the ready()d G actually runs and can hurt fairness when other Gs in the run queue are CPU hogs. For example, if there are three Gs sharing a P, one of which is a CPU hog that never voluntarily gives up the P and the other two of which are doing small amounts of work and communicating back and forth on an unbuffered channel, the two communicating Gs will get very little CPU time. Change this so that when G1 ready()s G2 and then blocks, the scheduler immediately hands off the remainder of G1's time slice to G2. In the above example, the two communicating Gs will now act as a unit and together get half of the CPU time, while the CPU hog gets the other half of the CPU time. This fixes the problem demonstrated by the ping-pong benchmark added in the previous commit: benchmark old ns/op new ns/op delta BenchmarkPingPongHog 684287 825 -99.88% On the x/benchmarks suite, this change improves the performance of garbage by ~6% (for GOMAXPROCS=1 and 4), and json by 28% and 36% for GOMAXPROCS=1 and 4. It has negligible effect on heap size. This has no effect on the go1 benchmark suite since those benchmarks are mostly single-threaded. Change-Id: I858a08eaa78f702ea98a5fac99d28a4ac91d339f Reviewed-on: https://go-review.googlesource.com/9289Reviewed-by:
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Austin Clements authored
This benchmark demonstrates a current problem with the scheduler where a set of frequently communicating goroutines get very little CPU time in the presence of another goroutine that hogs that CPU, even if one of those communicating goroutines is always runnable. Currently it takes about 0.5 milliseconds to switch between ping-ponging goroutines in the presence of a CPU hog: BenchmarkPingPongHog 2000 684287 ns/op Change-Id: I278848c84f778de32344921ae8a4a8056e4898b0 Reviewed-on: https://go-review.googlesource.com/9288Reviewed-by:
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Austin Clements authored
There are a variety of places where we check if a P's run queue is empty. This test is about to get slightly more complicated, so factor it out into a new function, runqempty. This function is inlinable, so this has no effect on performance. Change-Id: If4a0b01ffbd004937de90d8d686f6ded4aad2c6b Reviewed-on: https://go-review.googlesource.com/9287Reviewed-by:
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Russ Cox authored
We can expand the test cases as we discover problems. This is some basic tests plus all the things I got wrong in some recent work. Change-Id: Id875fcfaf74eb087ae42b441fe47a34c5b8ccb39 Reviewed-on: https://go-review.googlesource.com/9158Reviewed-by:
Austin Clements <austin@google.com>
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Aamir Khan authored
Explicitly specify that we represent polynomial in reversed notation Fixes #8229 Change-Id: Idf094c01fd82f133cd0c1b50fa967d12c577bdb5 Reviewed-on: https://go-review.googlesource.com/9237Reviewed-by:
David Chase <drchase@google.com>
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Shenghou Ma authored
Some machines are so slow that even with the default timeoutScale, they still timeout some tests. For example, currently some linux/arm builders and the openbsd/arm builder are timing out the runtime test and CL 8397 was proposed to skip some tests on openbsd/arm to fix the build. Instead of increasing timeoutScale or skipping tests, this CL introduces an environment variable $GO_TEST_TIMEOUT_SCALE that could be set to manually set a larger timeoutScale for those machines/builders. Fixes #10314. Change-Id: I16c9a9eb980d6a63309e4cacd79eee2fe05769ee Reviewed-on: https://go-review.googlesource.com/9223Reviewed-by:
Brad Fitzpatrick <bradfitz@golang.org>
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Srdjan Petrovic authored
Forward signals to signal handlers installed before Go installs its own, under certain circumstances. In particular, as iant@ suggests, signals are forwarded iff: (1) a non-SIG_DFL signal handler existed before Go, and (2) signal is synchronous (i.e., one of SIGSEGV, SIGBUS, SIGFPE), and (3a) signal occured on a non-Go thread, or (3b) signal occurred on a Go thread but in CGo code. Supported only on Linux, for now. Change-Id: I403219ee47b26cf65da819fb86cf1ec04d3e25f5 Reviewed-on: https://go-review.googlesource.com/8712Reviewed-by:
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Egon Elbre authored
benchmark old ns/op new ns/op delta BenchmarkEncodeToString 31281 23821 -23.85% BenchmarkDecodeString 156508 82254 -47.44% benchmark old MB/s new MB/s speedup BenchmarkEncodeToString 261.88 343.89 1.31x BenchmarkDecodeString 69.80 132.81 1.90x Change-Id: I115e0b18c3a6d5ef6bfdcb3f637644f02f290907 Reviewed-on: https://go-review.googlesource.com/8808Reviewed-by:
Nigel Tao <nigeltao@golang.org>
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- 23 Apr, 2015 11 commits
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Josh Bleecher Snyder authored
They are vestiges of the c2go transition. Change-Id: I22672e40373ef77d7a0bf69cfff8017e46353055 Reviewed-on: https://go-review.googlesource.com/9265Reviewed-by:
Minux Ma <minux@golang.org>
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Josh Bleecher Snyder authored
benchmark old ns/op new ns/op delta BenchmarkAddVV_1 18.7 14.8 -20.86% BenchmarkAddVV_2 21.8 16.6 -23.85% BenchmarkAddVV_3 26.1 17.1 -34.48% BenchmarkAddVV_4 30.4 21.9 -27.96% BenchmarkAddVV_5 35.5 19.8 -44.23% BenchmarkAddVV_1e1 63.0 28.3 -55.08% BenchmarkAddVV_1e2 593 178 -69.98% BenchmarkAddVV_1e3 5691 1490 -73.82% BenchmarkAddVV_1e4 56868 20761 -63.49% BenchmarkAddVV_1e5 569062 207679 -63.51% BenchmarkAddVW_1 15.8 12.6 -20.25% BenchmarkAddVW_2 17.8 13.1 -26.40% BenchmarkAddVW_3 21.2 13.9 -34.43% BenchmarkAddVW_4 23.6 14.7 -37.71% BenchmarkAddVW_5 26.0 15.8 -39.23% BenchmarkAddVW_1e1 41.3 21.6 -47.70% BenchmarkAddVW_1e2 383 145 -62.14% BenchmarkAddVW_1e3 3703 1264 -65.87% BenchmarkAddVW_1e4 36920 14359 -61.11% BenchmarkAddVW_1e5 370345 143046 -61.37% BenchmarkAddMulVVW_1 33.2 32.5 -2.11% BenchmarkAddMulVVW_2 58.0 57.2 -1.38% BenchmarkAddMulVVW_3 95.2 93.9 -1.37% BenchmarkAddMulVVW_4 108 106 -1.85% BenchmarkAddMulVVW_5 159 156 -1.89% BenchmarkAddMulVVW_1e1 344 340 -1.16% BenchmarkAddMulVVW_1e2 3644 3624 -0.55% BenchmarkAddMulVVW_1e3 37344 37208 -0.36% BenchmarkAddMulVVW_1e4 373295 372170 -0.30% BenchmarkAddMulVVW_1e5 3438116 3425606 -0.36% BenchmarkBitLen0 7.21 4.32 -40.08% BenchmarkBitLen1 6.49 4.32 -33.44% BenchmarkBitLen2 7.23 4.32 -40.25% BenchmarkBitLen3 6.49 4.32 -33.44% BenchmarkBitLen4 7.22 4.32 -40.17% BenchmarkBitLen5 6.52 4.33 -33.59% BenchmarkBitLen8 7.22 4.32 -40.17% BenchmarkBitLen9 6.49 4.32 -33.44% BenchmarkBitLen16 8.66 4.32 -50.12% BenchmarkBitLen17 7.95 4.32 -45.66% BenchmarkBitLen31 8.69 4.32 -50.29% BenchmarkGCD10x10 5021 5033 +0.24% BenchmarkGCD10x100 5571 5572 +0.02% BenchmarkGCD10x1000 6707 6729 +0.33% BenchmarkGCD10x10000 13526 13419 -0.79% BenchmarkGCD10x100000 85668 83242 -2.83% BenchmarkGCD100x100 24196 23936 -1.07% BenchmarkGCD100x1000 28802 27309 -5.18% BenchmarkGCD100x10000 64111 51704 -19.35% BenchmarkGCD100x100000 385840 274385 -28.89% BenchmarkGCD1000x1000 262892 236269 -10.13% BenchmarkGCD1000x10000 371393 277883 -25.18% BenchmarkGCD1000x100000 1311795 589055 -55.10% BenchmarkGCD10000x10000 9596740 6123930 -36.19% BenchmarkGCD10000x100000 16404000 7269610 -55.68% BenchmarkGCD100000x100000 776660000 419270000 -46.02% BenchmarkHilbert 13478980 13402270 -0.57% BenchmarkBinomial 9802 9440 -3.69% BenchmarkBitset 142 142 +0.00% BenchmarkBitsetNeg 328 279 -14.94% BenchmarkBitsetOrig 853 861 +0.94% BenchmarkBitsetNegOrig 1489 1444 -3.02% BenchmarkMul 420949000 410481000 -2.49% BenchmarkExp3Power0x10 1148 1229 +7.06% BenchmarkExp3Power0x40 1322 1376 +4.08% BenchmarkExp3Power0x100 2437 2486 +2.01% BenchmarkExp3Power0x400 9456 9346 -1.16% BenchmarkExp3Power0x1000 113623 108701 -4.33% BenchmarkExp3Power0x4000 1134933 1101481 -2.95% BenchmarkExp3Power0x10000 10773570 10396160 -3.50% BenchmarkExp3Power0x40000 101362100 97788300 -3.53% BenchmarkExp3Power0x100000 921114000 885249000 -3.89% BenchmarkExp3Power0x400000 8323094000 7969020000 -4.25% BenchmarkFibo 322021600 92554450 -71.26% BenchmarkScanPi 1264583 321065 -74.61% BenchmarkStringPiParallel 1644661 554216 -66.30% BenchmarkScan10Base2 1111 1080 -2.79% BenchmarkScan100Base2 6645 6345 -4.51% BenchmarkScan1000Base2 84084 62405 -25.78% BenchmarkScan10000Base2 3105998 932551 -69.98% BenchmarkScan100000Base2 257234800 40113333 -84.41% BenchmarkScan10Base8 571 573 +0.35% BenchmarkScan100Base8 2810 2543 -9.50% BenchmarkScan1000Base8 47383 25834 -45.48% BenchmarkScan10000Base8 2739518 567203 -79.30% BenchmarkScan100000Base8 253952400 36495680 -85.63% BenchmarkScan10Base10 553 556 +0.54% BenchmarkScan100Base10 2640 2385 -9.66% BenchmarkScan1000Base10 50865 24049 -52.72% BenchmarkScan10000Base10 3279916 549313 -83.25% BenchmarkScan100000Base10 309121000 36213140 -88.29% BenchmarkScan10Base16 478 483 +1.05% BenchmarkScan100Base16 2353 2144 -8.88% BenchmarkScan1000Base16 48091 24246 -49.58% BenchmarkScan10000Base16 2858886 586475 -79.49% BenchmarkScan100000Base16 266320000 38190500 -85.66% BenchmarkString10Base2 736 730 -0.82% BenchmarkString100Base2 2695 2707 +0.45% BenchmarkString1000Base2 20549 20388 -0.78% BenchmarkString10000Base2 212638 210782 -0.87% BenchmarkString100000Base2 1944963 1938033 -0.36% BenchmarkString10Base8 524 517 -1.34% BenchmarkString100Base8 1326 1320 -0.45% BenchmarkString1000Base8 8213 8249 +0.44% BenchmarkString10000Base8 72204 72092 -0.16% BenchmarkString100000Base8 769068 765993 -0.40% BenchmarkString10Base10 1018 982 -3.54% BenchmarkString100Base10 3485 3206 -8.01% BenchmarkString1000Base10 37102 18935 -48.97% BenchmarkString10000Base10 188633 88637 -53.01% BenchmarkString100000Base10 124490300 19700940 -84.17% BenchmarkString10Base16 509 502 -1.38% BenchmarkString100Base16 1084 1098 +1.29% BenchmarkString1000Base16 5641 5650 +0.16% BenchmarkString10000Base16 46900 46745 -0.33% BenchmarkString100000Base16 508957 505840 -0.61% BenchmarkLeafSize0 8934320 8149465 -8.78% BenchmarkLeafSize1 237666 118381 -50.19% BenchmarkLeafSize2 237807 117854 -50.44% BenchmarkLeafSize3 1688640 353494 -79.07% BenchmarkLeafSize4 235676 116196 -50.70% BenchmarkLeafSize5 2121896 430325 -79.72% BenchmarkLeafSize6 1682306 351775 -79.09% BenchmarkLeafSize7 1051847 251436 -76.10% BenchmarkLeafSize8 232697 115674 -50.29% BenchmarkLeafSize9 2403616 488443 -79.68% BenchmarkLeafSize10 2120975 429545 -79.75% BenchmarkLeafSize11 2023789 426525 -78.92% BenchmarkLeafSize12 1684830 351985 -79.11% BenchmarkLeafSize13 1465529 337906 -76.94% BenchmarkLeafSize14 1050498 253872 -75.83% BenchmarkLeafSize15 683228 197384 -71.11% BenchmarkLeafSize16 232496 116026 -50.10% BenchmarkLeafSize32 245841 126671 -48.47% BenchmarkLeafSize64 301728 190285 -36.93% Change-Id: I63e63297896d96b89c9a275b893c2b405a7e105d Reviewed-on: https://go-review.googlesource.com/9260Reviewed-by:
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Srdjan Petrovic authored
This addresses iant's comments from CL 9164. Change-Id: I7b5b282f61b11aab587402c2d302697e76666376 Reviewed-on: https://go-review.googlesource.com/9222Reviewed-by:
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Austin Clements authored
Currently, it's possible for the next_gc calculation to underflow. Since next_gc is unsigned, this wraps around and effectively disables GC for the rest of the program's execution. Besides being obviously wrong, this is causing test failures on 32-bit because some tests are running out of heap. This underflow happens for two reasons, both having to do with how we estimate the reachable heap size at the end of the GC cycle. One reason is that this calculation depends on the value of heap_live at the beginning of the GC cycle, but we currently only record that value during a concurrent GC and not during a forced STW GC. Fix this by moving the recorded value from gcController to work and recording it on a common code path. The other reason is that we use the amount of allocation during the GC cycle as an approximation of the amount of floating garbage and subtract it from the marked heap to estimate the reachable heap. However, since this is only an approximation, it's possible for the amount of allocation during the cycle to be *larger* than the marked heap size (since the runtime allocates white and it's possible for these allocations to never be made reachable from the heap). Currently this causes wrap-around in our estimate of the reachable heap size, which in turn causes wrap-around in next_gc. Fix this by bottoming out the reachable heap estimate at 0, in which case we just fall back to triggering GC at heapminimum (which is okay since this only happens on small heaps). Fixes #10555, fixes #10556, and fixes #10559. Change-Id: Iad07b529c03772356fede2ae557732f13ebfdb63 Reviewed-on: https://go-review.googlesource.com/9286 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by:
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Rick Hudson authored
To achieve a 2% improvement in the garbage benchmark this CL removes an unneeded assert and avoids one hbits.next() call per object being scanned. Change-Id: Ibd542d01e9c23eace42228886f9edc488354df0d Reviewed-on: https://go-review.googlesource.com/9244Reviewed-by:
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Hyang-Ah Hana Kim authored
newosproc0 does not work on android/arm. See issue #10548. Change-Id: Ieaf6f5d0b77cddf5bf0b6c89fd12b1c1b8723f9b Reviewed-on: https://go-review.googlesource.com/9293Reviewed-by:
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Nigel Tao authored
lands exactly on an IDAT row boundary. Fixes #10493 Change-Id: I12be7c5bdcde7032e17ed1d4400db5f17c72bc87 Reviewed-on: https://go-review.googlesource.com/9270Reviewed-by:
Rob Pike <r@golang.org>
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Dmitry Savintsev authored
github.com/kr/goven says it's deprecated and anyway it would be preferable to point users to a standard Go tool. Change-Id: Iac4a0d13233604a36538748d498f5770b2afce19 Reviewed-on: https://go-review.googlesource.com/8969Reviewed-by:
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Brad Fitzpatrick authored
If the machine's network configuration files (resolv.conf, nsswitch.conf) don't have any unsupported options, prefer Go's DNS resolver, which doesn't have the cgo & thread over. It means users can have more than 500 DNS requests outstanding (our current limit for cgo lookups) and not have one blocked thread per outstanding request. Discussed in thread https://groups.google.com/d/msg/golang-dev/2ZUi792oztM/Q0rg_DkF5HMJ Change-Id: I3f685d70aff6b47bec30b63e9fba674b20507f95 Reviewed-on: https://go-review.googlesource.com/8945Reviewed-by:
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Josh Bleecher Snyder authored
They are vestiges of the c2go translation. Change-Id: I9a10536f5986b751a35cc7d84b5ba69ae0c2ede7 Reviewed-on: https://go-review.googlesource.com/9262Reviewed-by:
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Nigel Tao authored
MiB. Fixes #10531 Change-Id: I9eece86837c3df2b1f7df315d5ec94bd3ede3eec Reviewed-on: https://go-review.googlesource.com/9238 Run-TryBot: Nigel Tao <nigeltao@golang.org> Reviewed-by:
Matthew Dempsky <mdempsky@google.com>
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- 22 Apr, 2015 10 commits
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Shenghou Ma authored
There is an assumption that the function executed in child thread created by runtime.close should not return. And different systems enforce that differently: some exit that thread, some exit the whole process. The test TestNewOSProc0 introduced in CL 9161 breaks that assumption, so we need to adjust the code to only exit the thread should the called function return. Change-Id: Id631cb2f02ec6fbd765508377a79f3f96c6a2ed6 Reviewed-on: https://go-review.googlesource.com/9246Reviewed-by:
Dave Cheney <dave@cheney.net>
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Shenghou Ma authored
It was only visible when you run godoc with explicit GOOS=windows, which is less useful for people developing portable application on non-windows platforms. Also added a note that log/syslog is not supported on NaCl. Change-Id: I81650445fb2a5ee161da7e0608c3d3547d5ac2a6 Reviewed-on: https://go-review.googlesource.com/9245Reviewed-by:
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Michael Hudson-Doyle authored
The constants in cmd/internal/goobj had gone stale (we had three copies of these constants, working on reducing that was what got me to noticing this). Some of the changes to link.hello.darwin.amd64 are the change from absolute to %rip-relative addressing, a change which happened quite a while ago... Depends on http://golang.org/cl/9113. Fixes #10501. Change-Id: Iaa1511f458a32228c2df2ccd0076bb9ae212a035 Reviewed-on: https://go-review.googlesource.com/9105Reviewed-by:
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Austin Clements authored
Currently, we set the heap goal for the next GC cycle using the size of the marked heap at the end of the current cycle. This can lead to a bad feedback loop if the mutator is rapidly allocating and releasing pointers that can significantly bloat heap size. If the GC were STW, the marked heap size would be exactly the reachable heap size (call it stwLive). However, in concurrent GC, marked=stwLive+floatLive, where floatLive is the amount of "floating garbage": objects that were reachable at some point during the cycle and were marked, but which are no longer reachable by the end of the cycle. If the GC cycle is short, then the mutator doesn't have much time to create floating garbage, so marked≈stwLive. However, if the GC cycle is long and the mutator is allocating and creating floating garbage very rapidly, then it's possible that marked≫stwLive. Since the runtime currently sets the heap goal based on marked, this will cause it to set a high heap goal. This means that 1) the next GC cycle will take longer because of the larger heap and 2) the assist ratio will be low because of the large distance between the trigger and the goal. The combination of these lets the mutator produce even more floating garbage in the next cycle, which further exacerbates the problem. For example, on the garbage benchmark with GOMAXPROCS=1, this causes the heap to grow to ~500MB and the garbage collector to retain upwards of ~300MB of heap, while the true reachable heap size is ~32MB. This, in turn, causes the GC cycle to take upwards of ~3 seconds. Fix this bad feedback loop by estimating the true reachable heap size (stwLive) and using this rather than the marked heap size (stwLive+floatLive) as the basis for the GC trigger and heap goal. This breaks the bad feedback loop and causes the mutator to assist more, which decreases the rate at which it can create floating garbage. On the same garbage benchmark, this reduces the maximum heap size to ~73MB, the retained heap to ~40MB, and the duration of the GC cycle to ~200ms. Change-Id: I7712244c94240743b266f9eb720c03802799cdd1 Reviewed-on: https://go-review.googlesource.com/9177Reviewed-by:
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Michael Hudson-Doyle authored
Change-Id: I429402dd91243cd9415b054ee17bfebccc68ed57 Reviewed-on: https://go-review.googlesource.com/9197Reviewed-by:
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Austin Clements authored
This may or may not be useful to the end user, but it's incredibly useful for us to understand the behavior of the pacer. Currently this is fairly easy (though not trivial) to derive from the other heap stats we print, but we're about to change how we compute the goal, which will make it much harder to derive. Change-Id: I796ef233d470c01f606bd9929820c01ece1f585a Reviewed-on: https://go-review.googlesource.com/9176Reviewed-by:
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Austin Clements authored
The trigger controller computes GC CPU utilization by dividing by the wall-clock time that's passed since concurrent mark began. Since this delta is nanoseconds it's borderline impossible for it to be zero, but if it is zero we'll currently divide by zero. Be robust to this possibility by ignoring the utilization in the error term if no time has elapsed. Change-Id: I93dfc9e84735682af3e637f6538d1e7602634f09 Reviewed-on: https://go-review.googlesource.com/9175Reviewed-by:
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Michael Hudson-Doyle authored
To make the gcprog for global data containing variables of types defined in other shared libraries, we need to know a lot about those types. So read the value of any symbol with a name starting with "type.". If a type uses a mask, the name of the symbol defining the mask unfortunately cannot be predicted from the type name so I have to keep track of the addresses of every such symbol and associate them with the type symbols after the fact. I'm not very happy about this change, but something like this is needed and this is as pleasant as I know how to make it. Change-Id: I408d831b08b3b31e0610688c41367b23998e975c Reviewed-on: https://go-review.googlesource.com/8334Reviewed-by:
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Michael Hudson-Doyle authored
There were 10 implementations of the trivial bool2int function, 9 of which were the only thing in their file. Remove all of them in favor of one in cmd/internal/obj. Change-Id: I9c51d30716239df51186860b9842a5e9b27264d3 Reviewed-on: https://go-review.googlesource.com/9230Reviewed-by:
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Alan Donovan authored
since the "precision" parameter means constant arithmetic is not necessarily exact. As requested by gri, within go/types, the local import name 'exact' has been kept, to reduce the diff with the x/tools branch. This may be changed later. Since the go/types.bash script was already obsolete, I added a comment to this effect. Tested with all.bash. Change-Id: I45153688d9d8afa8384fb15229b0124c686059b4 Reviewed-on: https://go-review.googlesource.com/9242Reviewed-by:
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