diff options
author | Jamie Liu <jamieliu@google.com> | 2019-07-30 20:31:29 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2019-07-30 20:32:29 -0700 |
commit | a7d5e0d254f22dc7d76f7f5bc86b8793f67e2f5f (patch) | |
tree | 08de71f2fb6d1fd73d054990f880e81fbb23bd1c /pkg/sentry/fs/fsutil | |
parent | 5afa642deb190dbacee225d05f58de69f775d3f3 (diff) |
Cache pages in CachingInodeOperations.Read when memory evictions are delayed.
PiperOrigin-RevId: 260851452
Diffstat (limited to 'pkg/sentry/fs/fsutil')
-rw-r--r-- | pkg/sentry/fs/fsutil/inode_cached.go | 77 |
1 files changed, 55 insertions, 22 deletions
diff --git a/pkg/sentry/fs/fsutil/inode_cached.go b/pkg/sentry/fs/fsutil/inode_cached.go index ed62049a9..e70bc28fb 100644 --- a/pkg/sentry/fs/fsutil/inode_cached.go +++ b/pkg/sentry/fs/fsutil/inode_cached.go @@ -568,21 +568,30 @@ type inodeReadWriter struct { // ReadToBlocks implements safemem.Reader.ReadToBlocks. func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) { + mem := rw.c.mfp.MemoryFile() + fillCache := !rw.c.useHostPageCache() && mem.ShouldCacheEvictable() + // Hot path. Avoid defers. - rw.c.dataMu.RLock() + var unlock func() + if fillCache { + rw.c.dataMu.Lock() + unlock = rw.c.dataMu.Unlock + } else { + rw.c.dataMu.RLock() + unlock = rw.c.dataMu.RUnlock + } // Compute the range to read. if rw.offset >= rw.c.attr.Size { - rw.c.dataMu.RUnlock() + unlock() return 0, io.EOF } end := fs.ReadEndOffset(rw.offset, int64(dsts.NumBytes()), rw.c.attr.Size) if end == rw.offset { // dsts.NumBytes() == 0? - rw.c.dataMu.RUnlock() + unlock() return 0, nil } - mem := rw.c.mfp.MemoryFile() var done uint64 seg, gap := rw.c.cache.Find(uint64(rw.offset)) for rw.offset < end { @@ -592,7 +601,7 @@ func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) { // Get internal mappings from the cache. ims, err := mem.MapInternal(seg.FileRangeOf(seg.Range().Intersect(mr)), usermem.Read) if err != nil { - rw.c.dataMu.RUnlock() + unlock() return done, err } @@ -602,7 +611,7 @@ func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) { rw.offset += int64(n) dsts = dsts.DropFirst64(n) if err != nil { - rw.c.dataMu.RUnlock() + unlock() return done, err } @@ -610,27 +619,48 @@ func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) { seg, gap = seg.NextNonEmpty() case gap.Ok(): - // Read directly from the backing file. - gapmr := gap.Range().Intersect(mr) - dst := dsts.TakeFirst64(gapmr.Length()) - n, err := rw.c.backingFile.ReadToBlocksAt(rw.ctx, dst, gapmr.Start) - done += n - rw.offset += int64(n) - dsts = dsts.DropFirst64(n) - // Partial reads are fine. But we must stop reading. - if n != dst.NumBytes() || err != nil { - rw.c.dataMu.RUnlock() - return done, err + gapMR := gap.Range().Intersect(mr) + if fillCache { + // Read into the cache, then re-enter the loop to read from the + // cache. + reqMR := memmap.MappableRange{ + Start: uint64(usermem.Addr(gapMR.Start).RoundDown()), + End: fs.OffsetPageEnd(int64(gapMR.End)), + } + optMR := gap.Range() + err := rw.c.cache.Fill(rw.ctx, reqMR, maxFillRange(reqMR, optMR), mem, usage.PageCache, rw.c.backingFile.ReadToBlocksAt) + mem.MarkEvictable(rw.c, pgalloc.EvictableRange{optMR.Start, optMR.End}) + seg, gap = rw.c.cache.Find(uint64(rw.offset)) + if !seg.Ok() { + unlock() + return done, err + } + // err might have occurred in part of gap.Range() outside + // gapMR. Forget about it for now; if the error matters and + // persists, we'll run into it again in a later iteration of + // this loop. + } else { + // Read directly from the backing file. + dst := dsts.TakeFirst64(gapMR.Length()) + n, err := rw.c.backingFile.ReadToBlocksAt(rw.ctx, dst, gapMR.Start) + done += n + rw.offset += int64(n) + dsts = dsts.DropFirst64(n) + // Partial reads are fine. But we must stop reading. + if n != dst.NumBytes() || err != nil { + unlock() + return done, err + } + + // Continue. + seg, gap = gap.NextSegment(), FileRangeGapIterator{} } - // Continue. - seg, gap = gap.NextSegment(), FileRangeGapIterator{} - default: break } } - rw.c.dataMu.RUnlock() + unlock() return done, nil } @@ -700,7 +730,10 @@ func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error seg, gap = seg.NextNonEmpty() case gap.Ok() && gap.Start() < mr.End: - // Write directly to the backing file. + // Write directly to the backing file. At present, we never fill + // the cache when writing, since doing so can convert small writes + // into inefficient read-modify-write cycles, and we have no + // mechanism for detecting or avoiding this. gapmr := gap.Range().Intersect(mr) src := srcs.TakeFirst64(gapmr.Length()) n, err := rw.c.backingFile.WriteFromBlocksAt(rw.ctx, src, gapmr.Start) |