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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/runtime/mksizeclasses.go | |
| 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/runtime/mksizeclasses.go')
| -rw-r--r-- | src/runtime/mksizeclasses.go | 6 |
1 files changed, 5 insertions, 1 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 |