From: Daniel Gustafsson <dgustafsson@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: llvmjit: Use explicit LLVMContextRef for inlining
Date: Fri, 17 Nov 2023 10:29:50 +0000
Message-ID: <E1r3w6g-005ro1-7n@gemulon.postgresql.org> (raw)
llvmjit: Use explicit LLVMContextRef for inlining
When performing inlining LLVM unfortunately "leaks" types (the
types survive and are usable, but a new round of inlining will
recreate new structurally equivalent types). This accumulation
will over time amount to a memory leak which for some queries
can be large enough to trigger the OOM process killer.
To avoid accumulation of types, all IR related data is stored
in an LLVMContextRef which is dropped and recreated in order
to release all types. Dropping and recreating incurs overhead,
so it will be done only after 100 queries. This is a heuristic
which might be revisited, but until we can get the size of the
context from LLVM we are flying a bit blind.
This issue has been reported several times, there may be more
references to it in the archives on top of the threads linked
below.
This is a backpatch of 9dce22033d5 to all supported branches.
Reported-By: Justin Pryzby <pryzby@telsasoft.com>
Reported-By: Kurt Roeckx <kurt@roeckx.be>
Reported-By: Jaime Casanova <jcasanov@systemguards.com.ec>
Reported-By: Lauri Laanmets <pcspets@gmail.com>
Author: Andres Freund and Daniel Gustafsson
Discussion: https://postgr.es/m/7acc8678-df5f-4923-9cf6-e843131ae89d@www.fastmail.com
Discussion: https://postgr.es/m/20201218235607.GC30237@telsasoft.com
Discussion: https://postgr.es/m/CAPH-tTxLf44s3CvUUtQpkDr1D8Hxqc2NGDzGXS1ODsfiJ6WSqA@mail.gmail.com
Backpatch-through: v12
Branch
------
REL_15_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/aef521849b68d1eeb63c3dfbc4e92d66dc94a636
Modified Files
--------------
src/backend/jit/llvm/llvmjit.c | 139 ++++++++++++++++++++++++++++----
src/backend/jit/llvm/llvmjit_deform.c | 77 +++++++++---------
src/backend/jit/llvm/llvmjit_expr.c | 60 +++++++-------
src/backend/jit/llvm/llvmjit_inline.cpp | 33 +++++---
src/include/jit/llvmjit.h | 8 ++
src/include/jit/llvmjit_emit.h | 30 ++++---
6 files changed, 244 insertions(+), 103 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: dgustafsson@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: llvmjit: Use explicit LLVMContextRef for inlining
In-Reply-To: <E1r3w6g-005ro1-7n@gemulon.postgresql.org>
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