view tests/test-censor2.t @ 51108:0250e45040f1

revlog: add a small cache of unfiltered chunk

This can provides a massive boost to the reading of multiple revision and the
computation of a valid delta chain.

This greatly help operation like `hg log --patch`, delta computation (helping
pull/unbundle), linkrev adjustment (helping copy tracing).

A first round of benchmark for `hg log --patch --limit 1000` shows improvement
in the 10-20% range on "small" repository like pypy or mercurial and large
improvements (about 33%) for more complex ones like netbeans and mozilla's.

These speeds up are consistent with the improvement to `hg pull` (from a server
sending poor deltas) I saw benchmarking this last year. Further benchmark will
be run during the freeze.

I added some configuration in the experimental space to be able to further test
the effect of various tuning for now. This feature should fit well in the
"usage/resource profile" configuration that we should land next cycle.

When it does not provides a benefit the overhead of the cache seem to be around
2%, a small price for the big improvement. In addition I believe we could shave
most of this overhead with a more efficent lru implementation.

  $ cat >> $HGRCPATH <<EOF
  > [censor]
  > policy=ignore
  > EOF

  $ mkdir r
  $ cd r
  $ hg init
  $ echo secret > target
  $ hg commit -Am "secret"
  adding target
  $ touch bystander
  $ hg commit -Am "innocent"
  adding bystander
  $ echo erased-secret > target
  $ hg commit -m "erased secret"
  $ hg censor target --config extensions.censor= -r ".^^"
  $ hg update ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  $ hg update tip
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved