• Memory usage: Working set much lower than Commit size

    From Anton Shepelev@21:1/5 to All on Tue Jun 3 11:51:59 2025
    Hello, all

    One of our clients' servers (VMWare guest) was sagging under
    RAM defficiency with nearly empty dm_exec_query_stats and
    dm_exec_cached_plans until we unabled Lock Pages in Memory
    for it:

    https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/enable-the-lock-pages-in-memory-option-windows?view=sql-server-ver17

    Now things look OK inisde MSSQL:

    SELECT
    info.physical_memory_kb / 1024 AS phys_mem_mb , -- 24 575
    info.committed_kb / 1024 AS committed_mb , -- 12 287
    info.committed_target_kb / 1024 AS ci_target_mb , -- 12 288
    buf .mb AS buf_size_mb , -- 10 246
    pmem.memory_utilization_percentage AS mem_util_perc, -- 100
    pmem.process_physical_memory_low AS phys_mem_low , -- 0
    ( SELECT COUNT(*) FROM sys.dm_exec_query_stats ) AS qstats_n , -- 11 887
    ( SELECT COUNT(*) FROM sys.dm_exec_cached_plans ) AS qplans_n -- 17 774
    FROM
    sys.dm_os_sys_info info,
    sys.dm_os_process_memory pmem,
    ( SELECT
    COUNT(*) * 8/1024 mb
    FROM sys.dm_os_buffer_descriptors
    ) buf

    But /Task Manager/ shows the following for sqlservr.exe:

    Working set: 254 084 K
    Commit size: 12 855 404 K

    Does it mean MSSQL has allocated 13G of RAM but is using
    only 254M? Or does the Working set somehow not include a
    lot of RAM that MSSQL is using with /Lock Pages in Memory/
    on?

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  • From Erland Sommarskog@21:1/5 to Anton Shepelev on Tue Jun 3 20:44:42 2025
    Anton Shepelev (anton.txt@g{oogle}mail.com) writes:
    Does it mean MSSQL has allocated 13G of RAM but is using
    only 254M? Or does the Working set somehow not include a
    lot of RAM that MSSQL is using with /Lock Pages in Memory/
    on?


    The latter.

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