From 9490b8da72088fe6f1b23c323749d977e3aa02f1 Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Fri, 25 Apr 2014 04:29:07 +0000 Subject: re PR go/60931 (libgo has issues when page size is not 4k) PR go/60931 runtime: Fix garbage collector issue with non 4kB system page size The go garbage collector tracks memory in terms of 4kB pages. Most of the code checks getpagesize() at runtime and does the right thing. On a 64kB ppc64 box I see SEGVs in long running processes which has been diagnosed as a bug in scavengelist. scavengelist does a madvise(MADV_DONTNEED) without rounding the arguments to the system page size. A strace of one of the failures shows the problem: madvise(0xc211030000, 4096, MADV_DONTNEED) = 0 The kernel rounds the length up to 64kB and we mark 60kB of valid data as no longer needed. Round start up to a system page and end down before calling madvise. From-SVN: r209777 --- libgo/runtime/mheap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'libgo') diff --git a/libgo/runtime/mheap.c b/libgo/runtime/mheap.c index fee493c..1b8ab79 100644 --- a/libgo/runtime/mheap.c +++ b/libgo/runtime/mheap.c @@ -387,7 +387,7 @@ forcegchelper(void *vnote) static uintptr scavengelist(MSpan *list, uint64 now, uint64 limit) { - uintptr released, sumreleased; + uintptr released, sumreleased, start, end, pagesize; MSpan *s; if(runtime_MSpanList_IsEmpty(list)) @@ -400,7 +400,17 @@ scavengelist(MSpan *list, uint64 now, uint64 limit) mstats.heap_released += released; sumreleased += released; s->npreleased = s->npages; - runtime_SysUnused((void*)(s->start << PageShift), s->npages << PageShift); + + start = s->start << PageShift; + end = start + (s->npages << PageShift); + + // Round start up and end down to ensure we + // are acting on entire pages. + pagesize = getpagesize(); + start = ROUND(start, pagesize); + end &= ~(pagesize - 1); + if(end > start) + runtime_SysUnused((void*)start, end - start); } } return sumreleased; -- cgit v1.1