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7b5ef8f2d0
We had a report from Stefan Kaltenbrunner of a case in which postmaster log files overran available disk space because multiple backends spewed enormous context stats dumps upon hitting an out-of-memory condition. Given the lack of similar reports, this isn't a common problem, but it still seems worth doing something about. However, we don't want to just blindly truncate the output, because that might prevent diagnosis of OOM problems. What seems like a workable compromise is to limit the dump to 100 child contexts per parent, and summarize the space used within any additional child contexts. That should help because practical cases where the dump gets long will typically be huge numbers of siblings under the same parent context; while the additional debugging value from seeing details about individual siblings beyond 100 will not be large, we hope. Anyway it doesn't take much code or memory space to do this, so let's try it like this and see how things go. Since the summarization mechanism requires passing totals back up anyway, I took the opportunity to add a "grand total" line to the end of the printout.
100 lines
3.5 KiB
C
100 lines
3.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* memnodes.h
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* POSTGRES memory context node definitions.
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*
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*
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* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/nodes/memnodes.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef MEMNODES_H
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#define MEMNODES_H
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#include "nodes/nodes.h"
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/*
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* MemoryContextCounters
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* Summarization state for MemoryContextStats collection.
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*
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* The set of counters in this struct is biased towards AllocSet; if we ever
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* add any context types that are based on fundamentally different approaches,
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* we might need more or different counters here. A possible API spec then
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* would be to print only nonzero counters, but for now we just summarize in
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* the format historically used by AllocSet.
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*/
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typedef struct MemoryContextCounters
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{
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Size nblocks; /* Total number of malloc blocks */
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Size freechunks; /* Total number of free chunks */
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Size totalspace; /* Total bytes requested from malloc */
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Size freespace; /* The unused portion of totalspace */
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} MemoryContextCounters;
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/*
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* MemoryContext
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* A logical context in which memory allocations occur.
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*
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* MemoryContext itself is an abstract type that can have multiple
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* implementations, though for now we have only AllocSetContext.
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* The function pointers in MemoryContextMethods define one specific
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* implementation of MemoryContext --- they are a virtual function table
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* in C++ terms.
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*
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* Node types that are actual implementations of memory contexts must
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* begin with the same fields as MemoryContext.
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*
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* Note: for largely historical reasons, typedef MemoryContext is a pointer
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* to the context struct rather than the struct type itself.
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*/
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typedef struct MemoryContextMethods
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{
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void *(*alloc) (MemoryContext context, Size size);
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/* call this free_p in case someone #define's free() */
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void (*free_p) (MemoryContext context, void *pointer);
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void *(*realloc) (MemoryContext context, void *pointer, Size size);
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void (*init) (MemoryContext context);
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void (*reset) (MemoryContext context);
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void (*delete_context) (MemoryContext context);
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Size (*get_chunk_space) (MemoryContext context, void *pointer);
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bool (*is_empty) (MemoryContext context);
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void (*stats) (MemoryContext context, int level, bool print,
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MemoryContextCounters *totals);
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#ifdef MEMORY_CONTEXT_CHECKING
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void (*check) (MemoryContext context);
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#endif
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} MemoryContextMethods;
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typedef struct MemoryContextData
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{
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NodeTag type; /* identifies exact kind of context */
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/* these two fields are placed here to minimize alignment wastage: */
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bool isReset; /* T = no space alloced since last reset */
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bool allowInCritSection; /* allow palloc in critical section */
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MemoryContextMethods *methods; /* virtual function table */
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MemoryContext parent; /* NULL if no parent (toplevel context) */
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MemoryContext firstchild; /* head of linked list of children */
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MemoryContext nextchild; /* next child of same parent */
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char *name; /* context name (just for debugging) */
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MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
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} MemoryContextData;
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/* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
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/*
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* MemoryContextIsValid
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* True iff memory context is valid.
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*
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* Add new context types to the set accepted by this macro.
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*/
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#define MemoryContextIsValid(context) \
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((context) != NULL && \
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(IsA((context), AllocSetContext)))
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#endif /* MEMNODES_H */
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