What causes "Log Memory size or PageCount must be specified" in microsoft/garnet?

Ensure at least one of MemorySize (>0) or PageCount (>0) is set before initialization; default MemorySize (16GiB) satisfies this.

microsoft/garnet · error · TsavoriteException

Log Memory size or PageCount must be specified

Error message

Log Memory size or PageCount must be specified

What it means

Thrown in the MaxAllocatedPageCount sizing step: the allocator needs either a positive MemorySize (to derive page count = MemorySize / PageSize) or a positive PageCount to size the circular buffer directly. With MemorySize <= 0 and PageCount <= 0 it cannot compute the buffer size. This overlaps with the constructor's error 221 guard but lives on the buffer-sizing path; it also catches a negative MemorySize that slipped past earlier validation.

Source

Thrown at libs/storage/Tsavorite/cs/src/core/Allocator/AllocatorBase.cs:626

            // Page size
            LogPageSizeBits = logSettings.PageSizeBits;
            PageSize = 1 << LogPageSizeBits;
            PageSizeMask = PageSize - 1;

            // Total HLOG size and MaxAllocatedPageCount. There are a couple ways MaxAllocatedPageCount can be set here; once set it
            // will never be exceeded by AllocatedPageCount, even if memory usage falls below logSettings.MemorySize. Memory
            // size tracking will be enforced only if this.logSizeTracker is set; otherwise, we set the MaxAllocatedPageCount here and
            // do not control heap memory usage.
            if (logSettings.MemorySize > 0)
            {
                // If LogSettings.PageCount is specified it becomes MaxAllocatedPageCount; otherwise MaxAllocatedPageCount will be
                // MaxMemorySize divided by page size.
                MaxAllocatedPageCount = logSettings.PageCount > 0 ? logSettings.PageCount : (int)(logSettings.MemorySize / PageSize);
            }
            else
            {
                if (logSettings.PageCount <= 0)
                    throw new TsavoriteException($"Log Memory size or PageCount must be specified");
                MaxAllocatedPageCount = logSettings.PageCount;
            }
            BufferSize = (int)NextPowerOf2(MaxAllocatedPageCount);

            BufferSizeMask = BufferSize - 1;

            logMutableFraction = logSettings.MutableFraction;

            // Segment size
            LogSegmentSizeBits = logSettings.SegmentSizeBits;
            SegmentSize = 1L << LogSegmentSizeBits;
            if (SegmentSize < PageSize)
                throw new TsavoriteException($"Segment ({SegmentSize}) must be at least of page size ({PageSize})");

            PageStatusIndicator = new FullPageStatus[BufferSize];

            if (!IsNullDevice)
            {

View on GitHub (pinned to 951b0fc683)

Solutions

Ensure at least one of MemorySize (>0) or PageCount (>0) is set before initialization; default MemorySize (16GiB) satisfies this.
If you zeroed MemorySize for a ReadOnly log, set PageCount explicitly.
Do not bypass the standard constructor validation; if you do, replicate these checks upstream.

Example fix

// before
logSettings.MemorySize = 0;
logSettings.PageCount  = 0;
// after
logSettings.PageCount = 64;   // size the ring by page count

Defensive patterns

Strategy: validation

Validate before calling

if (logSettings.MemorySize <= 0 && logSettings.PageCount <= 0)
    throw new ArgumentException("Log MemorySize (>0) or PageCount (>0) must be specified for buffer sizing.");

Try / catch

try { /* allocator init / Initialize */ }
catch (TsavoriteException ex) when (ex.Message.Contains("Memory size or PageCount must be specified"))
{ /* set MemorySize or PageCount to a positive value and reinitialize */ }

Prevention

Do not bypass the standard constructor validation; if you do, replicate this check upstream.
Ensure MemorySize or PageCount is positive before any Initialize call.
For ReadOnly logs keep MemorySize=0 but set PageCount.

When it happens

Trigger: Reaching page-buffer initialization with logSettings.MemorySize <= 0 and logSettings.PageCount <= 0 — e.g. a code path or subclass that bypassed the main validation block, or a negative MemorySize.

Common situations: Subclassing/customizing the allocator init sequence; a fork that reordered validation; calling an internal Initialize entry point directly with an under-specified LogSettings.

Related errors

AI-assisted analysis of microsoft/garnet@951b0fc683 (2026-08-13). Data as JSON: /api/errors/93ab4d9d294b973e. Report an issue: GitHub.