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| author | Matthew Dempsky <mdempsky@google.com> | 2021-03-12 16:58:10 -0800 |
|---|---|---|
| committer | Matthew Dempsky <mdempsky@google.com> | 2021-03-13 04:53:32 +0000 |
| commit | a8a85281caf21831ee51ea8c879cbba94bcce256 (patch) | |
| tree | 0cd1ff549dbdd3904d7580ae719228f4f4d82ad4 /src | |
| parent | 8e725f8452ac0ece548837a95d125bc67b9d8828 (diff) | |
| download | go-a8a85281caf21831ee51ea8c879cbba94bcce256.tar.xz | |
runtime: fix documented alignment of 32KiB and 64KiB size classes
As Cherry pointed out on golang.org/cl/299909, the page allocator
doesn't guarantee any alignment for multi-page allocations, so object
alignments are thus implicitly capped at page alignment.
Change-Id: I6f5df27f269b095cde54056f876fe4240f69c5c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/301292
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/runtime/mksizeclasses.go | 6 | ||||
| -rw-r--r-- | src/runtime/sizeclasses.go | 6 |
2 files changed, 8 insertions, 4 deletions
diff --git a/src/runtime/mksizeclasses.go b/src/runtime/mksizeclasses.go index ddbf1bf7fe..b1b10e9e02 100644 --- a/src/runtime/mksizeclasses.go +++ b/src/runtime/mksizeclasses.go @@ -239,7 +239,7 @@ func computeDivMagic(c *class) { func printComment(w io.Writer, classes []class) { fmt.Fprintf(w, "// %-5s %-9s %-10s %-7s %-10s %-9s %-9s\n", "class", "bytes/obj", "bytes/span", "objects", "tail waste", "max waste", "min align") prevSize := 0 - var minAligns [32]int + var minAligns [pageShift + 1]int for i, c := range classes { if i == 0 { continue @@ -249,6 +249,10 @@ func printComment(w io.Writer, classes []class) { tailWaste := spanSize - c.size*(spanSize/c.size) maxWaste := float64((c.size-prevSize-1)*objects+tailWaste) / float64(spanSize) alignBits := bits.TrailingZeros(uint(c.size)) + if alignBits > pageShift { + // object alignment is capped at page alignment + alignBits = pageShift + } for i := range minAligns { if i > alignBits { minAligns[i] = 0 diff --git a/src/runtime/sizeclasses.go b/src/runtime/sizeclasses.go index 65c72cfb1a..067871eaf3 100644 --- a/src/runtime/sizeclasses.go +++ b/src/runtime/sizeclasses.go @@ -62,7 +62,7 @@ package runtime // 56 12288 24576 2 0 11.45% 4096 // 57 13568 40960 3 256 9.99% 256 // 58 14336 57344 4 0 5.35% 2048 -// 59 16384 16384 1 0 12.49% 16384 +// 59 16384 16384 1 0 12.49% 8192 // 60 18432 73728 4 0 11.11% 2048 // 61 19072 57344 3 128 3.57% 128 // 62 20480 40960 2 0 6.87% 4096 @@ -70,7 +70,7 @@ package runtime // 64 24576 24576 1 0 11.45% 8192 // 65 27264 81920 3 128 10.00% 128 // 66 28672 57344 2 0 4.91% 4096 -// 67 32768 32768 1 0 12.50% 32768 +// 67 32768 32768 1 0 12.50% 8192 // alignment bits min obj size // 8 3 8 @@ -79,7 +79,7 @@ package runtime // 64 6 512 // 128 7 768 // 4096 12 28672 -// 32768 15 32768 +// 8192 13 32768 const ( _MaxSmallSize = 32768 |