revlog: use mmap by default is pre-population is available
Using mmap has a great impact of memory usage on server, and a good impact on
performance in multiple case. Now that we pre-populate memory mapping by
default, there is case where it using mmap is slower. So we use it by default
(if pre-population is available).
Further work to reduce the performance impact of the pre-population will be done
later.
Some benchmark below (using the same setup as
522b4d729e89):
As for
522b4d729e89 the impact on small repository like Mercurial or Pypy is
tiny, ~1% best. However for large repositories we see some performance
improvement without seeing the performance regression that we could have without
pre-populate.
##### For netbeans
### data-env-vars.name = netbeans-2018-08-01-zstd-sparse-revlog
## benchmark.name = hg.command.log
# bin-env-vars.hg.flavor = rust
# benchmark.variants.limit-rev = 1
# benchmark.variants.patch = yes
no-mmap: 0.171579
mmap: 0.166311 (-3.07%, -0.01)
# bin-env-vars.hg.flavor = default
no-mmap: 0.170716
mmap: 0.165218 (-3.22%, -0.01)
# benchmark.variants.patch = no
# benchmark.variants.rev = tip
no-mmap: 0.140862
mmap: 0.137566 (-2.34%, -0.00)
## benchmark.name = hg.command.unbundle
# bin-env-vars.hg.flavor = rust
# benchmark.variants.
issue6528 = disabled
# benchmark.variants.reuse-external-delta-parent = yes
# benchmark.variants.revs = any-1-extra-rev
# benchmark.variants.source = unbundle
no-mmap: 0.238038
mmap: 0.239912
no-populate: 0.cbd4c9 (+11.71%, +0.03)
#### For Mozilla
### data-env-vars.name = mozilla-try-2019-02-18-ds2-pnm
# benchmark.name = hg.command.log
# bin-env-vars.hg.flavor = rust
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.limit-rev = 1
# benchmark.variants.patch = yes
no-mmap: 0.258440
mmap: 0.237813 (-7.98%, -0.02)
# benchmark.variants.limit-rev = 10
no-mmap: 1.235323
mmap: 1.213578 (-1.76%, -0.02)
## benchmark.name = hg.command.push
# bin-env-vars.hg.flavor = rust
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.explicit-rev = none
# benchmark.variants.
issue6528 = disabled
# benchmark.variants.protocol = ssh
# benchmark.variants.reuse-external-delta-parent = yes
# benchmark.variants.revs = any-1-extra-rev
no-mmap: 4.790135
mmap: 4.668971 (-2.53%, -0.12)
no-populate: 4.841141 (+1.06%, +0.05)
### data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog
## benchmark.name = hg.command.log
# bin-env-vars.hg.flavor = default
# benchmark.variants.limit-rev = 1000
# benchmark.variants.rev = tip
no-mmap: 0.206187
mmap: 0.197348 (-4.29%, -0.01)
## benchmark.name = hg.command.push
# bin-env-vars.hg.flavor = default
# benchmark.variants.explicit-rev = none
# benchmark.variants.
issue6528 = disabled
# benchmark.variants.protocol = ssh
# benchmark.variants.reuse-external-delta-parent = yes
# benchmark.variants.revs = any-1-extra-rev
no-mmap: 4.768259
mmap: 4.798632
no-populate: 4.953295 (+3.88%, +0.19)
# benchmark.variants.revs = any-100-extra-rev
no-mmap: 4.785946
mmap: 4.903618
no-populate: 5.014963 (+4.79%, +0.23)
## benchmark.name = hg.command.unbundle
# bin-env-vars.hg.flavor = default
# benchmark.variants.
issue6528 = disabled
# benchmark.variants.reuse-external-delta-parent = yes
# benchmark.variants.revs = any-1-extra-rev
# benchmark.variants.source = unbundle
no-mmap: 1.400121
mmap: 1.423411
no-populate: 1.585365 (+13.23%, +0.19)