Tenant monitoring performance improvements #6868
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@@ Coverage Diff @@
## main #6868 +/- ##
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- Coverage 93.29% 92.68% -0.61%
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Files 272 272
Lines 57896 57935 +39
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- Hits 54012 53699 -313
- Misses 3884 4236 +352 |
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gokhangulbiz
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JelteF
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May 8, 2023
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| monitor->tenants = ShmemInitHash("citus_stats_tenants hash", | ||
| StatTenantsLimit * 3, StatTenantsLimit * 3, | ||
| &info, HASH_ELEM | HASH_FUNCTION | HASH_COMPARE | |
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By using HASH_BLOBS we can we can remove the hash and match functions, assuming that TenantStatsHashKey passes the assert_valid_hash_key2 check. See hash_helpers.{c,h}
JelteF
reviewed
May 8, 2023
| stats->score = 0; | ||
| stats->lastScoreReduction = 0; | ||
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| if (!found) |
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When would it ever be found? Seems like we could simplify this a little bit and pass in NULL instead of &found to hash_search.
JelteF
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May 8, 2023
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| CreateTenantStatsHashKey(char *tenantAttribute, uint32 colocationGroupId) | ||
| { | ||
| TenantStatsHashKey *key = (TenantStatsHashKey *) palloc(sizeof(TenantStatsHashKey)); | ||
| memset(key->tenantAttribute, 0, MAX_TENANT_ATTRIBUTE_LENGTH); | ||
| strlcpy(key->tenantAttribute, tenantAttribute, MAX_TENANT_ATTRIBUTE_LENGTH); | ||
| key->colocationGroupId = colocationGroupId; |
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nit/food for thought: It might be nice to fill in memory from the caller instead of allocating here. Then you can store the data on the stack instead of on the heap. (which should be a bit faster, and makes sure you don't need to use pfree)
Suggested change
| CreateTenantStatsHashKey(char *tenantAttribute, uint32 colocationGroupId) | |
| { | |
| TenantStatsHashKey *key = (TenantStatsHashKey *) palloc(sizeof(TenantStatsHashKey)); | |
| memset(key->tenantAttribute, 0, MAX_TENANT_ATTRIBUTE_LENGTH); | |
| strlcpy(key->tenantAttribute, tenantAttribute, MAX_TENANT_ATTRIBUTE_LENGTH); | |
| key->colocationGroupId = colocationGroupId; | |
| FillTenantStatsHashKey(TenantStatsHashKey *key, char *tenantAttribute, uint32 colocationGroupId) | |
| { | |
| memset(key->tenantAttribute, 0, MAX_TENANT_ATTRIBUTE_LENGTH); | |
| strlcpy(key->tenantAttribute, tenantAttribute, MAX_TENANT_ATTRIBUTE_LENGTH); | |
| key->colocationGroupId = colocationGroupId; |
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| TenantStatsHashKey *key = (TenantStatsHashKey *) palloc(sizeof(TenantStatsHashKey)); | ||
| FillTenantStatsHashKey(key, AttributeToTenant, AttributeToColocationGroupId); |
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What I meant as an advantage of this approach was that you can store TenantsStatsHashKey on the stack instead.
Suggested change
| TenantStatsHashKey *key = (TenantStatsHashKey *) palloc(sizeof(TenantStatsHashKey)); | |
| FillTenantStatsHashKey(key, AttributeToTenant, AttributeToColocationGroupId); | |
| TenantStatsHashKey key = {0}; | |
| FillTenantStatsHashKey(&key, AttributeToTenant, AttributeToColocationGroupId); |
JelteF
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May 15, 2023
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Code looks good now and benchmark results look great. Some extra benchmarks on machines with more cores would be needed to find the final impact of the new code, but the changes are clearly an improvement. If we are going to backport this we should be doing valgrind tests again.
gokhangulbiz
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Jun 12, 2023
- [x] Use spinlock instead of lwlock per tenant [b437aa9](b437aa9) - [x] Use hashtable to store tenant stats [ccd464b](ccd464b) - [x] Introduce a new GUC for specifying the sampling rate of new tenant entries in the tenant monitor. [a8d3805](a8d3805) Below are the pgbench metrics with select-only workloads from my local machine. Here is the [script](https://gist.github.com/gokhangulbiz/7a2308470597dc06734ff7c08f87c656) I used for benchmarking. | | Connection Count | Initial Implementation (TPS) | On/Off Diff | Final Implementation -Run#1 (TPS) | On/Off Diff | Final Implementation -Run#2 (TPS) | On/Off Diff | Final Implementation -Run#3 (TPS) | On/Off Diff | Avg On/Off Diff | | --- | ---------------- | ---------------------------- | ----------- | ---------------------------------- | ----------- | ---------------------------------- | ----------- | ---------------------------------- | ----------- | --------------- | | On | 32 | 37488.69839 | \-17% | 42859.94402 | \-5% | 43379.63121 | \-2% | 42636.2264 | \-7% | \-5% | | Off | 32 | 43909.83121 | | 45139.63151 | | 44188.77425 | | 45451.9548 | | | | On | 300 | 30463.03538 | \-15% | 33265.19957 | \-7% | 34685.87233 | \-2% | 34682.5214 | \-1% | \-3% | | Off | 300 | 35105.73594 | | 35637.45423 | | 35331.33447 | | 35113.3214 | | | (cherry picked from commit 2c509b7)
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Below are the pgbench metrics with select-only workloads from my local machine. Here is the script I used for benchmarking.