Here are some benchmark numbers I ran across when looking at different thread safe hash implementations:
Source: http://preshing.com/20160201/new-concurrent-hash-maps-for-cpp/ <http://preshing.com/20160201/new-concurrent-hash-maps-for-cpp/> -Bryan > On Sep 29, 2017, at 2:42 PM, Bryan Call <bc...@apache.org> wrote: > > TCL handles concurrency for memory allocation bits. Looking at it more, the > hashtable part of the library doesn’t support currency and you would have to > handle locking yourself. > > I created a test program to see when it was locking: > #include "ink_hash_table.h" > #include <stdlib.h> > #include <iostream> > > using namespace std; > > int main() { > const char *foo = "hello_world"; > InkHashTable *mine(ink_hash_table_create(InkHashTableKeyType_String)); > ink_hash_table_insert(mine, "foo", (void*)foo); > char *foo_check = nullptr; > ink_hash_table_lookup(mine, "foo", (void**)&foo_check); > cout << foo_check << endl; > } > > Breakpoint 3, 0x00007ffff5ea4da0 in pthread_mutex_lock () from > /lib64/libpthread.so.0 > (gdb) bt > #0 0x00007ffff5ea4da0 in pthread_mutex_lock () from /lib64/libpthread.so.0 > #1 0x00007ffff65fe927 in ?? () from /lib64/libtcl8.6.so > #2 0x00007ffff65fed6d in TclpAlloc () from /lib64/libtcl8.6.so > #3 0x00007ffff65213c8 in Tcl_Alloc () from /lib64/libtcl8.6.so > #4 0x00007ffff65b6315 in ?? () from /lib64/libtcl8.6.so > #5 0x00007ffff65b64c7 in ?? () from /lib64/libtcl8.6.so > #6 0x00007ffff7bafe67 in ink_hash_table_get_entry (ht_ptr=<optimized out>, > key=<optimized out>, new_value=<optimized out>) at ink_hash_table.cc:244 > <http://ink_hash_table.cc:244/> > #7 0x00007ffff7bafeb6 in ink_hash_table_insert > (ht_ptr=ht_ptr@entry=0x614010, key=key@entry=0x400b3c "foo", > value=value@entry=0x400b30) at ink_hash_table.cc:293 > <http://ink_hash_table.cc:293/> > #8 0x0000000000400951 in main () at test_ink_hash_table.cc:10 > <http://test_ink_hash_table.cc:10/> > (gdb) cont > > -Bryan > > > >> On Sep 29, 2017, at 1:50 PM, CrazyCow <zhangzizhong0...@gmail.com >> <mailto:zhangzizhong0...@gmail.com>> wrote: >> >> I read the code of Tcl_HashTable. They say nothing about handling >> concurrency. >> >> The biggest concern about this is, as Alan and Bryan said, what level of use >> will we have for ATS. >> I read docs <https://www.threadingbuildingblocks.org/docs/help/index.htm> of >> TBB. It's offering rich tools of handling threading issues. We can look into >> it more to see if there are other utilities appealing. >> Generally speaking, nice docs, good reputation, and upcoming new releases >> are signs of tbb being a good choice. >> >> 2017-09-29 12:11 GMT-07:00 Bryan Call <bc...@apache.org >> <mailto:bc...@apache.org>>: >> This seems like a large dependency to pull in to get a thread safe unordered >> map. We already have a dependency on Tcl_HashTable (InkHashTable), that >> handles concurrency, and it used throughout the code base. >> >> -Bryan >> >> >> >>> On Sep 28, 2017, at 5:55 PM, CrazyCow <zhangzizhong0...@gmail.com >>> <mailto:zhangzizhong0...@gmail.com>> wrote: >>> >>> Hi, ATS devs, >>> >>> Currently, we have a requirement of concurrent_unordered_map (details can >>> be found https://github.com/apache/trafficserver/pull/2555 >>> <https://github.com/apache/trafficserver/pull/2555>). And >>> intel::tbb::concurrent_unordered_map is the most mature one we can try out. >>> I understand this dependency is huge. I'd like to hear opinions from you >>> guys, that whether we need to do it or not and if yes, what is the best >>> approach to introduce it. >>> >>> >>> Thanks, >>> Zizhong >> >> >
