Troubleshoot: `run_op_on_device` Error On Wormhole N150d

Introduction

Hey guys! Having trouble running run_op_on_device on your Wormhole n150d? You're not alone! This article dives into a common issue encountered on Ubuntu 22.04 when trying to execute the python3 -m ttnn.examples.usage.run_op_on_device script from the tt-metal repository. Specifically, we'll be tackling the dreaded "Insufficient number of hugepages" error, which often surfaces despite having IOMMU (Intel VT-d) enabled. We'll break down the problem, explore potential causes, and provide step-by-step solutions to get you back on track. So, let's get started and squash this bug together!

Understanding the Issue: Insufficient HugePages

When working with high-performance computing devices like the Wormhole n150d, efficient memory management is crucial. HugePages play a vital role in this, allowing the system to allocate memory in larger blocks, thus reducing the overhead associated with traditional memory management. This is particularly important for devices that perform a lot of data-intensive operations, as it minimizes translation lookaside buffer (TLB) misses and improves overall performance. The error message “Insufficient number of hugepages available, expected one per device (1) but have 0” indicates that the system hasn't allocated enough of these large memory pages for the device to function correctly. This issue often arises even when IOMMU (Input/Output Memory Management Unit) is enabled, which adds another layer of complexity. IOMMU is designed to enhance security and system stability by isolating devices from each other's memory spaces. However, it sometimes requires specific configurations to work harmoniously with HugePages.

The root cause of this error typically lies in either the HugePages not being properly allocated or the system not being configured to use them. Several factors can contribute to this, including incorrect kernel parameters, insufficient HugePages configuration in the system's memory settings, or even conflicts with other system settings. The error message itself points to the core of the problem: the system expects a certain number of HugePages to be available for each device, but it's finding none. This discrepancy can halt the execution of critical operations, such as run_op_on_device, which relies on efficient memory allocation for its computations. To effectively troubleshoot this issue, it's essential to verify the current HugePages settings, ensure that they meet the device's requirements, and check for any potential conflicts that might prevent their proper allocation.

Initial Error Report and System Configuration

Let's dive into the initial error report to understand the context better. The error occurred while attempting to run python3 -m ttnn.examples.usage.run_op_on_device on a Wormhole n150d device. The operating system in use is Ubuntu 22.04 Jammy Jellyfish, a popular Linux distribution known for its stability and wide range of software support. The tt-metal repository was at commit tag v0.62.0-rc7, indicating a specific version of the software being used. The Python version in use was Python 3.10.12, a stable release that ensures compatibility with the tt-metal codebase.

The error log provides valuable insights into the problem. It starts by displaying the initial ttnn configuration, which includes settings such as cache paths, flags for enabling or disabling features, and reporting options. The logs then show that the SiliconDriver successfully opened the PCI device, but it also reports that IOMMU is disabled. This is a crucial piece of information, as IOMMU is often a prerequisite for proper device operation. The logs further highlight warnings about insufficient NumHugepages, indicating that the system is not allocating enough HugePages for the device. The specific warning messages, such as “Insufficient NumHugepages: 0 should be at least NumMMIODevices: 1” and “no huge page mount found in /proc/mounts for path: /dev/hugepages-1G”, pinpoint the root cause of the issue. These messages suggest that the system is either not configured to allocate HugePages or that the allocated HugePages are not being mounted correctly. The final critical error message, “Machine setup error: Insufficient number of hugepages available”, confirms that this is a fatal issue that prevents the program from running.

Investigating IOMMU Status

The initial logs indicated that IOMMU was disabled, which raised a red flag. To verify the IOMMU status, the user ran sudo dmesg | grep -i -e dmar -e iommu. This command is a powerful tool for examining the kernel's message buffer and filtering for relevant information about IOMMU. The output of this command provided mixed signals. On one hand, it showed that IOMMU was enabled in the kernel command line via the iommu=pt parameter. This parameter instructs the kernel to use the pass-through mode for IOMMU, which is a common configuration. The logs also displayed details about the DMAR (DMA Remapping) hardware, including base addresses and capabilities, further suggesting that IOMMU was active at the hardware level. However, the logs also contained warning messages such as “[Firmware Bug]: RMRR entry for device 04:00.0 is broken - applying workaround” and inconsistencies in IOMMU features. These warnings hinted at potential firmware or hardware-related issues that could be affecting IOMMU's operation.

Additionally, the user ran find /sys/kernel/iommu_groups/ -type l. This command is used to check the IOMMU groups, which are a way of isolating devices from each other for security purposes. The output of this command showed a list of IOMMU groups and the devices assigned to them, further confirming that IOMMU was at least partially functional. However, the presence of the warnings in the dmesg output suggested that there might be underlying issues affecting IOMMU's stability or performance. This discrepancy between the apparent activation of IOMMU and the warning messages highlighted the need for a more thorough investigation into the system's IOMMU configuration. It's possible that while IOMMU is enabled at a basic level, certain features or functionalities might not be working correctly due to firmware bugs or other hardware-related issues. Addressing these warnings is crucial for ensuring the stable and reliable operation of the Wormhole n150d device.

Step-by-Step Guide to Resolving the HugePages Issue

Alright, let's get down to brass tacks and fix this HugePages problem! Here’s a step-by-step guide to help you troubleshoot and resolve the issue:

Step 1: Verify Current HugePages Configuration

First, we need to check how HugePages are currently configured on your system. Open your terminal and run the following commands:

cat /proc/meminfo | grep -i HugePages

This command will display information about HugePages, including the total number, the number that are free, and the default HugePage size. Pay close attention to the HugePages_Total value. If it's 0, then no HugePages are currently allocated, which is likely the root cause of your problem. We are focusing on HugePages because the system needs contiguous memory blocks for high-performance computing. This approach reduces memory fragmentation and improves overall system performance. We want to ensure these pages are available and correctly configured.

Step 2: Configure HugePages

If you find that HugePages_Total is 0, or if the number is less than what the tt-metal software requires (at least one per device), you'll need to configure HugePages. To do this, you need to modify the kernel command-line parameters. Here's how:

1. Edit the GRUB configuration file:

sudo nano /etc/default/grub ```

2. Add or modify the GRUB_CMDLINE_LINUX_DEFAULT line to include the hugepages parameter. For example, to allocate 1024 HugePages of 2MB each, add the following:

   GRUB_CMDLINE_LINUX_DEFAULT=