diff options
Diffstat (limited to 'pkg/sentry/pgalloc/pgalloc.go')
| -rw-r--r-- | pkg/sentry/pgalloc/pgalloc.go | 122 |
1 files changed, 64 insertions, 58 deletions
diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go index 626d1eaa4..7c297fb9e 100644 --- a/pkg/sentry/pgalloc/pgalloc.go +++ b/pkg/sentry/pgalloc/pgalloc.go @@ -29,6 +29,7 @@ import ( "syscall" "time" + "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/log" "gvisor.dev/gvisor/pkg/safemem" @@ -224,6 +225,18 @@ type usageInfo struct { refs uint64 } +// canCommit returns true if the tracked region can be committed. +func (u *usageInfo) canCommit() bool { + // refs must be greater than 0 because we assume that reclaimable pages + // (that aren't already known to be committed) are not committed. This + // isn't necessarily true, even after the reclaimer does Decommit(), + // because the kernel may subsequently back the hugepage-sized region + // containing the decommitted page with a hugepage. However, it's + // consistent with our treatment of unallocated pages, which have the same + // property. + return !u.knownCommitted && u.refs != 0 +} + // An EvictableMemoryUser represents a user of MemoryFile-allocated memory that // may be asked to deallocate that memory in the presence of memory pressure. type EvictableMemoryUser interface { @@ -828,6 +841,11 @@ func (f *MemoryFile) UpdateUsage() error { log.Debugf("UpdateUsage: skipped with usageSwapped!=0.") return nil } + // Linux updates usage values at CONFIG_HZ. + if scanningAfter := time.Now().Sub(f.usageLast).Milliseconds(); scanningAfter < time.Second.Milliseconds()/linux.CLOCKS_PER_SEC { + log.Debugf("UpdateUsage: skipped because previous scan happened %d ms back", scanningAfter) + return nil + } f.usageLast = time.Now() err = f.updateUsageLocked(currentUsage, mincore) @@ -841,7 +859,7 @@ func (f *MemoryFile) UpdateUsage() error { // pages by invoking checkCommitted, which is a function that, for each page i // in bs, sets committed[i] to 1 if the page is committed and 0 otherwise. // -// Precondition: f.mu must be held. +// Precondition: f.mu must be held; it may be unlocked and reacquired. func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func(bs []byte, committed []byte) error) error { // Track if anything changed to elide the merge. In the common case, we // expect all segments to be committed and no merge to occur. @@ -868,7 +886,7 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func( } else if f.usageSwapped != 0 { // We have more usage accounted for than the file itself. // That's fine, we probably caught a race where pages were - // being committed while the above loop was running. Just + // being committed while the below loop was running. Just // report the higher number that we found and ignore swap. usage.MemoryAccounting.Dec(f.usageSwapped, usage.System) f.usageSwapped = 0 @@ -880,21 +898,9 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func( // Iterate over all usage data. There will only be usage segments // present when there is an associated reference. - for seg := f.usage.FirstSegment(); seg.Ok(); seg = seg.NextSegment() { - val := seg.Value() - - // Already known to be committed; ignore. - if val.knownCommitted { - continue - } - - // Assume that reclaimable pages (that aren't already known to be - // committed) are not committed. This isn't necessarily true, even - // after the reclaimer does Decommit(), because the kernel may - // subsequently back the hugepage-sized region containing the - // decommitted page with a hugepage. However, it's consistent with our - // treatment of unallocated pages, which have the same property. - if val.refs == 0 { + for seg := f.usage.FirstSegment(); seg.Ok(); { + if !seg.ValuePtr().canCommit() { + seg = seg.NextSegment() continue } @@ -917,56 +923,53 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func( } // Query for new pages in core. - if err := checkCommitted(s, buf); err != nil { + // NOTE(b/165896008): mincore (which is passed as checkCommitted) + // by f.UpdateUsage() might take a really long time. So unlock f.mu + // while checkCommitted runs. + f.mu.Unlock() + err := checkCommitted(s, buf) + f.mu.Lock() + if err != nil { checkErr = err return } // Scan each page and switch out segments. - populatedRun := false - populatedRunStart := 0 - for i := 0; i <= bufLen; i++ { - // We run past the end of the slice here to - // simplify the logic and only set populated if - // we're still looking at elements. - populated := false - if i < bufLen { - populated = buf[i]&0x1 != 0 - } - - switch { - case populated == populatedRun: - // Keep the run going. - continue - case populated && !populatedRun: - // Begin the run. - populatedRun = true - populatedRunStart = i - // Keep going. + seg := f.usage.LowerBoundSegment(r.Start) + for i := 0; i < bufLen; { + if buf[i]&0x1 == 0 { + i++ continue - case !populated && populatedRun: - // Finish the run by changing this segment. - runRange := memmap.FileRange{ - Start: r.Start + uint64(populatedRunStart*usermem.PageSize), - End: r.Start + uint64(i*usermem.PageSize), + } + // Scan to the end of this committed range. + j := i + 1 + for ; j < bufLen; j++ { + if buf[j]&0x1 == 0 { + break } - seg = f.usage.Isolate(seg, runRange) - seg.ValuePtr().knownCommitted = true - // Advance the segment only if we still - // have work to do in the context of - // the original segment from the for - // loop. Otherwise, the for loop itself - // will advance the segment - // appropriately. - if runRange.End != r.End { - seg = seg.NextSegment() + } + committedFR := memmap.FileRange{ + Start: r.Start + uint64(i*usermem.PageSize), + End: r.Start + uint64(j*usermem.PageSize), + } + // Advance seg to committedFR.Start. + for seg.Ok() && seg.End() < committedFR.Start { + seg = seg.NextSegment() + } + // Mark pages overlapping committedFR as committed. + for seg.Ok() && seg.Start() < committedFR.End { + if seg.ValuePtr().canCommit() { + seg = f.usage.Isolate(seg, committedFR) + seg.ValuePtr().knownCommitted = true + amount := seg.Range().Length() + usage.MemoryAccounting.Inc(amount, seg.ValuePtr().kind) + f.usageExpected += amount + changedAny = true } - amount := runRange.Length() - usage.MemoryAccounting.Inc(amount, val.kind) - f.usageExpected += amount - changedAny = true - populatedRun = false + seg = seg.NextSegment() } + // Continue scanning for committed pages. + i = j + 1 } // Advance r.Start. @@ -978,6 +981,9 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func( if err != nil { return err } + + // Continue with the first segment after r.End. + seg = f.usage.LowerBoundSegment(r.End) } return nil |