1. 24 Apr, 2015 10 commits
    • Austin Clements's avatar
      runtime: use park/ready to wake up GC at end of concurrent mark · ce502b06
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarRuss Cox <rsc@golang.org>
      ce502b06
    • Austin Clements's avatar
      runtime: use timer for GC control revise rather than timeout · 4e32718d
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarRuss Cox <rsc@golang.org>
      4e32718d
    • Austin Clements's avatar
      runtime: yield time slice to most recently readied G · e870f06c
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarRuss Cox <rsc@golang.org>
      e870f06c
    • Austin Clements's avatar
      runtime: benchmark for ping-pong in the presence of a CPU hog · da0e37fa
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarRuss Cox <rsc@golang.org>
      da0e37fa
    • Austin Clements's avatar
      runtime: factor checking if P run queue is empty · e5e52f4f
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarRuss Cox <rsc@golang.org>
      e5e52f4f
    • Russ Cox's avatar
      cmd/internal/gc: add and test write barrier debug output · 9406f68e
      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: default avatarRick Hudson <rlh@golang.org>
      Reviewed-by: default avatarAustin Clements <austin@google.com>
      9406f68e
    • Aamir Khan's avatar
      hash/crc32: clarify documentation · 80f575b7
      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: default avatarDavid Chase <drchase@google.com>
      80f575b7
    • Shenghou Ma's avatar
      cmd/dist: allow $GO_TEST_TIMEOUT_SCALE to override timeoutScale · 7579867f
      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: default avatarBrad Fitzpatrick <bradfitz@golang.org>
      7579867f
    • Srdjan Petrovic's avatar
      runtime: signal forwarding · 5c8fbc6f
      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: default avatarIan Lance Taylor <iant@golang.org>
      5c8fbc6f
    • Egon Elbre's avatar
      encoding/base64: Optimize EncodeToString and DecodeString. · b075d1fc
      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: default avatarNigel Tao <nigeltao@golang.org>
      b075d1fc
  2. 23 Apr, 2015 11 commits
    • Josh Bleecher Snyder's avatar
      cmd/9g, etc: remove // fallthrough comments · 04829a41
      Josh Bleecher Snyder authored
      They are vestiges of the c2go transition.
      
      Change-Id: I22672e40373ef77d7a0bf69cfff8017e46353055
      Reviewed-on: https://go-review.googlesource.com/9265Reviewed-by: default avatarMinux Ma <minux@golang.org>
      04829a41
    • Josh Bleecher Snyder's avatar
      math/big: add partial arm64 assembly support · 56a7c5b9
      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: default avatarDavid Crawshaw <crawshaw@golang.org>
      56a7c5b9
    • Srdjan Petrovic's avatar
      runtime: deflake TestNewOSProc0, fix _rt0_amd64_linux_lib stack alignment · 1f65c9c1
      Srdjan Petrovic authored
      This addresses iant's comments from CL 9164.
      
      Change-Id: I7b5b282f61b11aab587402c2d302697e76666376
      Reviewed-on: https://go-review.googlesource.com/9222Reviewed-by: default avatarIan Lance Taylor <iant@golang.org>
      1f65c9c1
    • Austin Clements's avatar
      runtime: fix underflow in next_gc calculation · ed09e0e2
      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: default avatarRick Hudson <rlh@golang.org>
      ed09e0e2
    • Rick Hudson's avatar
      runtime: Improve scanning performance · 77f56af0
      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: default avatarAustin Clements <austin@google.com>
      77f56af0
    • Hyang-Ah Hana Kim's avatar
      runtime: disable TestNewOSProc0 on android/arm. · aef54d40
      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: default avatarDavid Crawshaw <crawshaw@golang.org>
      aef54d40
    • Nigel Tao's avatar
      image/png: don't silently swallow io.ReadFull's io.EOF error when it · ba8fa0e1
      Nigel Tao authored
      lands exactly on an IDAT row boundary.
      
      Fixes #10493
      
      Change-Id: I12be7c5bdcde7032e17ed1d4400db5f17c72bc87
      Reviewed-on: https://go-review.googlesource.com/9270Reviewed-by: default avatarRob Pike <r@golang.org>
      ba8fa0e1
    • Dmitry Savintsev's avatar
      doc/faq: replace reference to goven with gomvpkg · 133966d3
      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: default avatarMinux Ma <minux@golang.org>
      133966d3
    • Brad Fitzpatrick's avatar
      net: use Go's DNS resolver when system configuration permits · 4a0ba7aa
      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: default avatarIan Lance Taylor <iant@golang.org>
      Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
      4a0ba7aa
    • Josh Bleecher Snyder's avatar
      cmd/internal/gc: remove /*untyped*/ comments · c2312280
      Josh Bleecher Snyder authored
      They are vestiges of the c2go translation.
      
      Change-Id: I9a10536f5986b751a35cc7d84b5ba69ae0c2ede7
      Reviewed-on: https://go-review.googlesource.com/9262Reviewed-by: default avatarMinux Ma <minux@golang.org>
      c2312280
    • Nigel Tao's avatar
      image/jpeg: have the LargeImageWithShortData test only allocate 64 MiB, not 604 · 5e9ab665
      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: default avatarMatthew Dempsky <mdempsky@google.com>
      5e9ab665
  3. 22 Apr, 2015 19 commits