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When pagefiles are opened?

OSR_Community_UserOSR_Community_User Member Posts: 110,217
Hi All!

I have few questions about NT filesystems and page files:
1. When NT opens pagefiles?
2. How they are opened? Via IRP or FastIO? Are any special open flags present?
Do FS need initialize caching for pagefile?

Regards, Dennis


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Comments

  • OSR_Community_UserOSR_Community_User Member Posts: 110,217
    > Do FS need initialize caching for pagefile?

    Surely no. They are used for paging IO only - and all paging IO must bypass
    the cache.

    Max
  • OSR_Community_UserOSR_Community_User Member Posts: 110,217
    NT uses routine NtCreatePagingFile which looks like this:

    NTSYSAPI
    NTSTATUS
    NTAPI
    NtCreatePagingFile (
    IN PUNICODE_STRING PageFileName,
    IN PLARGE_INTEGER InitialSize,
    IN PLARGE_INTEGER MaximumSize,
    IN ULONG Reserved
    );

    This routine is usually called by SMSS.EXE after it performs
    some critical operations (autochecks, file renames etc.).
    There is a key in registry \Registry\Machine\System\CurrentControlSetControl\Session Manager\Memory management containing value
    PagingFiles of type REG_MULTI_SZ. This one contains list of:
    - file name (eg. D:\pagefile.sys),
    - initial size (eg. 43 [MB])
    - maximum size (eg. 65 [MB]) (optional).

    Routine NtCreatePagingFile calls IoCreateFile with Options
    IO_OPEN_PAGING_FILE. This is present in create irp stack
    location as SL_OPEN_PAGING_FILE.
    FS should in this moment read all allocation for this file
    to the resident memory and both the FCB and CCB should
    also be allocated from non-paged pool. This is because when
    processing the I/O to the paging file you have to translate file
    run into disk runs and call the disk driver - ie. no cache is
    maintained - and at this time also no page faults can occur.

    Paul

    > -----P?vodn? zpr?va-----
    > Od: Dennis [SMTP:[email protected]]
    > Odesl?no: 13. kv?tna 2000 1:39
    > Komu: File Systems Developers
    > P?edm?t: [ntfsd] When pagefiles are opened?
    >
    > Hi All!
    >
    > I have few questions about NT filesystems and page files:
    > 1. When NT opens pagefiles?
    > 2. How they are opened? Via IRP or FastIO? Are any special open flags
    > present?
    > Do FS need initialize caching for pagefile?
    >
    > Regards, Dennis
    >
    >
    >
    > __________________________________________________
    >
    > Do You Yahoo!?
    >
    > Talk to your friends online with Yahoo! Messenger.
    >
    > http://im.yahoo.com
    >
    >
    > ---
    > You are currently subscribed to ntfsd as: [email protected]
    > To unsubscribe send a blank email to $subst('Email.Unsub')
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