bug in SlabAlloc / VALGRIND_MAKE_MEM_DEFINED

Started by Tomas Vondraabout 9 years ago3 messageshackers
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#1Tomas Vondra
tomas.vondra@2ndquadrant.com

Hi,

Andres nagged to me about valgrind runs taking much longer since
9fab40ad introduced the SlabContext into reorderbuffer.c. And by
"longer" I mean hours instead of minutes.

After a bit of investigation I stumbled on this line in slab.c:

VALGRIND_MAKE_MEM_DEFINED(chunk, SlabChunkGetPointer(chunk));

which is wrong, because the second parameter should be size and not
another pointer. This essentially marks a lot of memory as defined,
which results in the extreme test runtime.

Instead, the line should be:

VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(int32));

Patch attached.

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachments:

slab-valgrind-fix.patchbinary/octet-stream; name=slab-valgrind-fix.patchDownload+1-1
#2Tomas Vondra
tomas.vondra@2ndquadrant.com
In reply to: Tomas Vondra (#1)
Re: bug in SlabAlloc / VALGRIND_MAKE_MEM_DEFINED

On 04/04/2017 10:42 PM, Tomas Vondra wrote:

Hi,

Andres nagged to me about valgrind runs taking much longer since
9fab40ad introduced the SlabContext into reorderbuffer.c. And by
"longer" I mean hours instead of minutes.

After a bit of investigation I stumbled on this line in slab.c:

VALGRIND_MAKE_MEM_DEFINED(chunk, SlabChunkGetPointer(chunk));

which is wrong, because the second parameter should be size and not
another pointer. This essentially marks a lot of memory as defined,
which results in the extreme test runtime.

Instead, the line should be:

VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(int32));

Patch attached.

Turns out SlabCheck() was missing VALGRIND_MAKE_MEM_DEFINED, resulting
in a valgrind failure with --enable-assert. Updated patch version
attached, passing all tests in test_decoding.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachments:

slab-valgrind-fix-v2.patchbinary/octet-stream; name=slab-valgrind-fix-v2.patchDownload+2-1
#3Andres Freund
andres@anarazel.de
In reply to: Tomas Vondra (#2)
Re: bug in SlabAlloc / VALGRIND_MAKE_MEM_DEFINED

On 2017-04-04 23:23:30 +0200, Tomas Vondra wrote:

On 04/04/2017 10:42 PM, Tomas Vondra wrote:

Hi,

Andres nagged to me about valgrind runs taking much longer since
9fab40ad introduced the SlabContext into reorderbuffer.c. And by
"longer" I mean hours instead of minutes.

After a bit of investigation I stumbled on this line in slab.c:

VALGRIND_MAKE_MEM_DEFINED(chunk, SlabChunkGetPointer(chunk));

which is wrong, because the second parameter should be size and not
another pointer. This essentially marks a lot of memory as defined,
which results in the extreme test runtime.

Instead, the line should be:

VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(int32));

Patch attached.

Turns out SlabCheck() was missing VALGRIND_MAKE_MEM_DEFINED, resulting in a
valgrind failure with --enable-assert. Updated patch version attached,
passing all tests in test_decoding.

Pushed, and re-enabled TestDecoding on skink.

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