hcq/MaxScale
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Remove unnecessary memory allocations

Browse Source 
Given the fact that there exist only three possible categories, the map
can be replaced with a static array that needs no memory
allocations. Making this array thread-local allows it to be reused which
places an upper limit on the number of memory allocations.
This commit is contained in:
Markus Mäkelä
2019-03-05 10:47:56 +02:00
parent e7f739e95d
commit a7be3c527c
1 changed files with 16 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
server/modules/routing/readwritesplit/rwsplit_select_backends.cc
View File

@ -22,6 +22,7 @@
#include <functional> #include <functional>
#include <random> #include <random>
#include <iostream> #include <iostream>
#include <array>
#include <maxbase/stopwatch.hh> #include <maxbase/stopwatch.hh>
#include <maxscale/router.h> #include <maxscale/router.h>
@ -201,6 +202,11 @@ BackendSelectFunction get_backend_select_function(select_criteria_t sc)
return backend_cmp_current_load; return backend_cmp_current_load;
} }
namespace
{
// Buffers for sorting the servers, thread_local to avoid repeated memory allocations
thread_local std::array<SRWBackendVector, 3> priority_map;
}
/** /**
* @brief Find the best slave candidate for routing reads. * @brief Find the best slave candidate for routing reads.
@ -216,7 +222,6 @@ SRWBackendVector::iterator find_best_backend(SRWBackendVector& backends,
bool masters_accepts_reads) bool masters_accepts_reads)
{ {
// Group backends by priority. The set of highest priority backends will then compete. // Group backends by priority. The set of highest priority backends will then compete.
std::map<int, SRWBackendVector> priority_map;
int best_priority {INT_MAX}; // low numbers are high priority int best_priority {INT_MAX}; // low numbers are high priority
for (auto& psBackend : backends) for (auto& psBackend : backends)
@ -230,16 +235,16 @@ SRWBackendVector::iterator find_best_backend(SRWBackendVector& backends,
{ {
if (!is_busy) if (!is_busy)
{ {
priority = 1; // highest priority, idle servers priority = 0; // highest priority, idle servers
} }
else else
{ {
priority = 13; // lowest priority, busy servers priority = 2; // lowest priority, busy servers
} }
} }
else else
{ {
priority = 2; // idle masters with masters_accept_reads==false priority = 1; // idle masters with masters_accept_reads==false
} }
priority_map[priority].push_back(psBackend); priority_map[priority].push_back(psBackend);
@ -247,8 +252,14 @@ SRWBackendVector::iterator find_best_backend(SRWBackendVector& backends,
} }
auto best = select(priority_map[best_priority]); auto best = select(priority_map[best_priority]);
auto rval = std::find(backends.begin(), backends.end(), *best);
return std::find(backends.begin(), backends.end(), *best); for (auto& a : priority_map)
{
a.clear();
}
return rval;
} }
/** /**