User Guide


ITLB Overhead

Metric Description

In x86 architectures, mappings between virtual and physical memory are facilitated by a page table, which is kept in memory. To minimize references to this table, recently-used portions of the page table are cached in a hierarchy of 'translation look-aside buffers', or TLBs, which are consulted on every virtual address translation. As with data caches, the farther a request has to go to be satisfied, the worse the performance impact. This metric estimates the performance penalty of page walks induced on ITLB (instruction TLB) misses.

Possible Issues

A significant proportion of cycles is spent handling instruction TLB misses.


1. Use profile-guided optimization and IPO to reduce the size of hot code regions.
2. Consider compiler options to reorder functions so that hot functions are located together.
3. If your application makes significant use of macros, try to reduce this by either converting the relevant macros to functions or using linker options to eliminate repeated code.
4. For Windows targets, add function splitting.
5. Consider using large code pages.

Product and Performance Information


Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804