diff options
Diffstat (limited to 'pkg/sentry/platform/filemem/filemem.go')
| -rw-r--r-- | pkg/sentry/platform/filemem/filemem.go | 65 |
1 files changed, 58 insertions, 7 deletions
diff --git a/pkg/sentry/platform/filemem/filemem.go b/pkg/sentry/platform/filemem/filemem.go index 45ef98eb0..6c8b95578 100644 --- a/pkg/sentry/platform/filemem/filemem.go +++ b/pkg/sentry/platform/filemem/filemem.go @@ -105,6 +105,12 @@ type FileMem struct { usageSwapped uint64 usageLast time.Time + // minUnallocatedPage is the minimum page that may be unallocated. + // i.e., there are no unallocated pages below minUnallocatedPage. + // + // minUnallocatedPage is protected by mu. + minUnallocatedPage uint64 + // fileSize is the size of the backing memory file in bytes. fileSize is // always a power-of-two multiple of chunkSize. // @@ -119,6 +125,12 @@ type FileMem struct { // is protected by mu. reclaimable bool + // minReclaimablePage is the minimum page that may be reclaimable. + // i.e., all reclaimable pages are >= minReclaimablePage. + // + // minReclaimablePage is protected by mu. + minReclaimablePage uint64 + // reclaimCond is signaled (with mu locked) when reclaimable or destroyed // transitions from false to true. reclaimCond sync.Cond @@ -162,6 +174,9 @@ const ( chunkMask = chunkSize - 1 initialSize = chunkSize + + // maxPage is the highest 64-bit page. + maxPage = math.MaxUint64 &^ (usermem.PageSize - 1) ) // newFromFile creates a FileMem backed by the given file. @@ -172,6 +187,9 @@ func newFromFile(file *os.File) (*FileMem, error) { f := &FileMem{ fileSize: initialSize, file: file, + // No pages are reclaimable. DecRef will always be able to + // decrease minReclaimablePage from this point. + minReclaimablePage: maxPage, } f.reclaimCond.L = &f.mu f.mappings.Store(make([]uintptr, initialSize/chunkSize)) @@ -242,7 +260,7 @@ func (f *FileMem) Allocate(length uint64, kind usage.MemoryKind) (platform.FileR alignment = usermem.HugePageSize } - start := findUnallocatedRange(&f.usage, length, alignment) + start, minUnallocatedPage := findUnallocatedRange(&f.usage, f.minUnallocatedPage, length, alignment) end := start + length // File offsets are int64s. Since length must be strictly positive, end // cannot legitimately be 0. @@ -281,17 +299,36 @@ func (f *FileMem) Allocate(length uint64, kind usage.MemoryKind) (platform.FileR }) { panic(fmt.Sprintf("allocating %v: failed to insert into f.usage:\n%v", fr, &f.usage)) } + + if minUnallocatedPage < start { + f.minUnallocatedPage = minUnallocatedPage + } else { + // start was the first unallocated page. The next must be + // somewhere beyond end. + f.minUnallocatedPage = end + } + return fr, nil } -func findUnallocatedRange(usage *usageSet, length, alignment uint64) uint64 { +// findUnallocatedRange returns the first unallocated page in usage of the +// specified length and alignment beginning at page start and the first single +// unallocated page. +func findUnallocatedRange(usage *usageSet, start, length, alignment uint64) (uint64, uint64) { + // Only searched until the first page is found. + firstPage := start + foundFirstPage := false alignMask := alignment - 1 - var start uint64 - for seg := usage.FirstSegment(); seg.Ok(); seg = seg.NextSegment() { + for seg := usage.LowerBoundSegment(start); seg.Ok(); seg = seg.NextSegment() { r := seg.Range() + + if !foundFirstPage && r.Start > firstPage { + foundFirstPage = true + } + if start >= r.End { // start was rounded up to an alignment boundary from the end - // of a previous segment. + // of a previous segment and is now beyond r.End. continue } // This segment represents allocated or reclaimable pages; only the @@ -301,8 +338,11 @@ func findUnallocatedRange(usage *usageSet, length, alignment uint64) uint64 { break } start = (r.End + alignMask) &^ alignMask + if !foundFirstPage { + firstPage = r.End + } } - return start + return start, firstPage } // fallocate(2) modes, defined in Linux's include/uapi/linux/falloc.h. @@ -418,12 +458,15 @@ func (f *FileMem) findReclaimable() (platform.FileRange, bool) { // Allocate returns the first usable range in offset order and is // currently a linear scan, so reclaiming from the beginning of the // file minimizes the expected latency of Allocate. - for seg := f.usage.FirstSegment(); seg.Ok(); seg = seg.NextSegment() { + for seg := f.usage.LowerBoundSegment(f.minReclaimablePage); seg.Ok(); seg = seg.NextSegment() { if seg.ValuePtr().refs == 0 { + f.minReclaimablePage = seg.End() return seg.Range(), true } } f.reclaimable = false + // No pages are reclaimable. + f.minReclaimablePage = maxPage } } @@ -450,6 +493,10 @@ func (f *FileMem) markReclaimed(fr platform.FileRange) { // caller of markReclaimed may not have decommitted it, so we can only mark // fr as reclaimed. f.usage.Remove(f.usage.Isolate(seg, fr)) + if fr.Start < f.minUnallocatedPage { + // We've deallocated at least one lower page. + f.minUnallocatedPage = fr.Start + } } // MapInto implements platform.File.MapInto. @@ -533,6 +580,10 @@ func (f *FileMem) DecRef(fr platform.FileRange) { f.usage.MergeAdjacent(fr) if freed { + if fr.Start < f.minReclaimablePage { + // We've freed at least one lower page. + f.minReclaimablePage = fr.Start + } f.reclaimable = true f.reclaimCond.Signal() } |