Mercurial > hg
view tests/test-propertycache.py.out @ 30212:260af19891f2
changegroup: increase write buffer size to 128k
By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.
This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.
It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.
When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).
This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Sun, 16 Oct 2016 13:35:23 -0700 |
parents | 9789670992d6 |
children |
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=== property cache === calllog: [] cached value (unfiltered): NOCACHE = first access on unfiltered, should do a call access: 0 calllog: [0] cached value (unfiltered): 0 = second access on unfiltered, should not do call access 0 calllog: [0] cached value (unfiltered): 0 = first access on "visible" view, should do a call cached value ("visible" view): NOCACHE access: 7 calllog: [0, 7] cached value (unfiltered): 0 cached value ("visible" view): 7 = second access on "visible view", should not do call access: 7 calllog: [0, 7] cached value (unfiltered): 0 cached value ("visible" view): 7 = no effect on other view cached value ("immutable" view): NOCACHE access: 9 calllog: [0, 7, 9] cached value (unfiltered): 0 cached value ("visible" view): 7 cached value ("immutable" view): 9 === unfiltered property cache === unficalllog: [] cached value (unfiltered): NOCACHE cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE = first access on unfiltered, should do a call access (unfiltered): 100 unficalllog: [100] cached value (unfiltered): 100 = second access on unfiltered, should not do call access (unfiltered): 100 unficalllog: [100] cached value (unfiltered): 100 = access on view should use the unfiltered cache access (unfiltered): 100 access ("visible" view): 100 access ("immutable" view): 100 unficalllog: [100] cached value (unfiltered): 100 cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE = even if we clear the unfiltered cache cached value (unfiltered): NOCACHE cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE unficalllog: [100] access ("visible" view): 100 unficalllog: [100, 100] cached value (unfiltered): 100 cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE access ("immutable" view): 100 unficalllog: [100, 100] cached value (unfiltered): 100 cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE access (unfiltered): 100 unficalllog: [100, 100] cached value (unfiltered): 100 cached value ("visible" view): NOCACHE cached value ("immutable" view): NOCACHE