PS-11161 [8.0]: mem_root_deque performance optimizations (part 1).#5949
Open
dlenev wants to merge 1 commit into
Open
PS-11161 [8.0]: mem_root_deque performance optimizations (part 1).#5949dlenev wants to merge 1 commit into
dlenev wants to merge 1 commit into
Conversation
Reduce target size of mem_root_deque block to 256 bytes from 1Kb. In the majority of cases mem_root_deque is used to store pointers (e.g. to Item objects), hence the 1kB block can store up to 128 elements for 64-bit arch. OTOH in many cases the number of elements which is really used in mem_root_deque is much lower. For example, for many queries number of fields in SELECT list is far smaller than 64. This means that in many cases the bigger part of such a 1kB block is just wasted. Taking into account that there are 5-10 of mem_root_deque instances even for fairly simple queries the effect of such waste becomes more pronounced - allocating these extra unnecessary 5-10Kb on main MEM_ROOT can trigger it to request another block from malloc(). And the latter has small but visible impact on performance in some of sysbench tests.
dlenev
force-pushed
the
ps-11161-step-1-8.0
branch
from
23cbdb9 to
f1da129
Compare
Contributor
Author
|
Here are Jenkins results for this change: https://ps80.cd.percona.com/view/8.0%20+%208.4%20parallel%20MTR/job/percona-server-8.0-pipeline-parallel-mtr/1593/ |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Reduce target size of mem_root_deque block to 256 bytes from 1Kb.
In the majority of cases mem_root_deque is used to store pointers (e.g. to Item objects), hence the 1kB block can store up to 128 elements for 64-bit arch.
OTOH in many cases the number of elements which is really used in mem_root_deque is much lower. For example, for many queries number of fields in SELECT list is far smaller than 64.
This means that in many cases the bigger part of such a 1kB block is just wasted. Taking into account that there are 5-10 of mem_root_deque instances even for fairly simple queries the effect of such waste becomes more pronounced - allocating these extra unnecessary 5-10Kb on main MEM_ROOT can trigger it to request another block from malloc(). And the latter has small but visible impact on performance in some of sysbench tests.