4GB Limit on large_pages shared memory set-up
General
Escalation
General
Escalation
Description
Environment
None
AFFECTED CS IDs
249759
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George Lorch August 16, 2019 at 4:25 PM
Sveta Smirnova March 27, 2019 at 7:10 AM
Copying relevant part of the source code invetigation from the upstream bug report:
If I set a breakpoint at shmget call:
https://github.com/mysql/mysql-server/blob/5.7/storage/innobase/os/os0proc.cc#L91
(gdb) p *n
$4 = 4397727744
(gdb) p size
$5 = 102760448size is calculated as:
size = ut_2pow_round(*n + (os_large_page_size - 1),
os_large_page_size);Round is defined as:
#define ut_2pow_round(n, m) (👎 & ~((m) - 1))(gdb) p (( *n + (os_large_page_size - 1) ) & ~(( os_large_page_size ) - 1))
$6 = 102760448The result became correct after converting ~((m) - 1) to uint64_t:
(gdb) p (( *n + (os_large_page_size - 1) ) & ~(( os_large_page_size ) - 1UL))
$7 = 4397727744
Done
Details
Details
Assignee
Zsolt Parragi
Zsolt ParragiReporter
Nickolay Ihalainen
Nickolay Ihalainen(Deactivated)Labels
Time tracking
4h 22m logged
Priority
MediumSmart Checklist
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Created March 24, 2019 at 8:52 AM
Updated March 6, 2024 at 12:15 PM
Resolved July 4, 2019 at 11:06 AM
Large pages allocations with innodb buffer pool chunk 4GB and more causing incorrect size for memory segment.
--large-pages --innodb_buffer_pool_chunk_size=4G
I've started mysqld as root, but it's also possible to see the same issue with proper value for /proc/sys/vm/hugetlb_shm_group:
https://dev.mysql.com/doc/refman/8.0/en/large-page-support.html
sync; echo 3 > /proc/sys/vm/drop_caches
echo 5120 > /proc/sys/vm/nr_hugepages # 10GB
ulimit -l unlimited
bin/mysqld --no-defaults --user=root --datadir=$PWD/data --lc-messages-dir=$PWD/share/english --initialize-insecure --skip-networking
bin/mysqld --no-defaults --user=root --datadir=$PWD/data --lc-messages-dir=$PWD/share/english --socket=$PWD/data/mysqld.sock --skip-networking --innodb_buffer_pool_instances=2 --large-pages --innodb_buffer_pool_chunk_size=4G --innodb_buffer_pool_size=8G
ipcs -m