Re: [Tarantool-patches] [PATCH] sql: increase default cache size

[Nikita Pettik <korablev@tarantool.org>]

On 28 Dec 11:54, Leonid Vasiliev wrote:
> Hi!
> 
> On 24.12.2020 19:57, Nikita Pettik wrote:
> > On 11 Dec 18:29, Leonid Vasiliev wrote:
> > 
> > IMHO before pushing performance aimed patches, we should carefully
> > review them. Could you run some SQL benchmarks to verify there's
> > no degradation on any case?
> 
> Can you tell me where we have benchmarks for SQL and how to run them?

We have tpc-h/tpc-c bench at least as I know:
https://github.com/tarantool/tpcc
https://github.com/tarantool/tpch

Please contact QA team to get instructions how to lauch them.
 
> > Also, does this change affect non-SQL
> > users? I mean does SQL tmp cache is lazy initialized or it allocates
> > all 20mb right on start? For sure, 18mb is not a lot memory in 2020,
> > but still it may turn out to be surprise for some users..
> 
> The memory allocation is done on per-request basis:
> "The default page cache implemention does not allocate the full amount
> of cache memory all at once. Cache memory is allocated in smaller chunks
> on an as-needed basis."

Ok, fine, at least it won't affect users which don't use SQL sub-system.
So then we should only make sure that cache increase only improves
SQL performance on standard benches.

> > > On 11.12.2020 15:09, Nikita Pettik wrote:
> > > > On 11 Dec 01:37, Leonid Vasiliev wrote:
> > > > > Increase the maximum number of in-memory pages to use
> > > > > for temporary tables.
> > > > > (https://www.sqlite.org/compile.html#default_cache_size)
> > > > > 
> > > > > Part of #5609
> > > > > ---
> > > > > 
> > > > > Hi SQL team. It is a simplest part of #5609.
> > > > > This patch increases the default SQL cache size by 10 times to 20 MB.
> > > > > A similar experiment shows a 10% performance increase for some datasets.
> > > > > (https://github.com/tarantool/tarantool/issues/5593#issuecomment-740044007).
> > > > > Mons approved these changes. I haven't done any research to determine the
> > > > > optimal value. So feel free to throw this patch away.
> > > > 
> > > > Hi, why not inroduce separate handler for user to change this setting?
> > > > Since SQLite is embedded database, almost all settings are set at
> > > > compile time. In constrast, we can move it to the box.
> > > > 
> > > 
> > > If I understood you correctly, the settings should be implemented when
> > > working on # 5609 (this path doesn't close the task). This is the
> > > simplest improvement to update the default.
> > > 
> > > > > https://github.com/tarantool/tarantool/issues/5609
> > > > > https://github.com/tarantool/tarantool/tree/lvasiliev/gh-5609-increase-default-sql-sort-cache-size
> > > > > 
> > > > >    src/box/CMakeLists.txt | 4 ++++
> > > > >    1 file changed, 4 insertions(+)
> > > > > 
> > > > > diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
> > > > > index 19203f7..7372179 100644
> > > > > --- a/src/box/CMakeLists.txt
> > > > > +++ b/src/box/CMakeLists.txt
> > > > > @@ -218,6 +218,10 @@ if(CMAKE_BUILD_TYPE STREQUAL "Debug")
> > > > >      add_definitions(-DSQL_DEBUG=1)
> > > > >    endif()
> > > > >    add_definitions(-DSQL_TEST=1)
> > > > > +# Set the maximum number of in-memory pages to use for temporary tables.
> > > > > +# 20000 * 1024 = 20480000 bytes.
> > > > > +# (https://www.sqlite.org/compile.html#default_cache_size)
> > > > > +add_definitions(-DSQL_DEFAULT_CACHE_SIZE=-20000)
> > > > >    set(EXT_SRC_DIR ${CMAKE_SOURCE_DIR}/extra)
> > > > >    set(EXT_BIN_DIR ${CMAKE_BINARY_DIR}/extra)
> > > > > -- 
> > > > > 2.7.4
> > > > >