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Diffstat (limited to 'Documentation/powerpc/ppc_htab.txt')
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diff --git a/Documentation/powerpc/ppc_htab.txt b/Documentation/powerpc/ppc_htab.txt deleted file mode 100644 index 8b8c7df29fa..00000000000 --- a/Documentation/powerpc/ppc_htab.txt +++ /dev/null @@ -1,118 +0,0 @@ - Information about /proc/ppc_htab -===================================================================== - -This document and the related code was written by me (Cort Dougan), please -email me (cort@fsmlabs.com) if you have questions, comments or corrections. - -Last Change: 2.16.98 - -This entry in the proc directory is readable by all users but only -writable by root. - -The ppc_htab interface is a user level way of accessing the -performance monitoring registers as well as providing information -about the PTE hash table. - -1. Reading - - Reading this file will give you information about the memory management - hash table that serves as an extended tlb for page translation on the - powerpc. It will also give you information about performance measurement - specific to the cpu that you are using. - - Explanation of the 604 Performance Monitoring Fields: - MMCR0 - the current value of the MMCR0 register - PMC1 - PMC2 - the value of the performance counters and a - description of what events they are counting - which are based on MMCR0 bit settings. - Explanation of the PTE Hash Table fields: - - Size - hash table size in Kb. - Buckets - number of buckets in the table. - Address - the virtual kernel address of the hash table base. - Entries - the number of ptes that can be stored in the hash table. - User/Kernel - how many pte's are in use by the kernel or user at that time. - Overflows - How many of the entries are in their secondary hash location. - Percent full - ratio of free pte entries to in use entries. - Reloads - Count of how many hash table misses have occurred - that were fixed with a reload from the linux tables. - Should always be 0 on 603 based machines. - Non-error Misses - Count of how many hash table misses have occurred - that were completed with the creation of a pte in the linux - tables with a call to do_page_fault(). - Error Misses - Number of misses due to errors such as bad address - and permission violations. This includes kernel access of - bad user addresses that are fixed up by the trap handler. - - Note that calculation of the data displayed from /proc/ppc_htab takes - a long time and spends a great deal of time in the kernel. It would - be quite hard on performance to read this file constantly. In time - there may be a counter in the kernel that allows successive reads from - this file only after a given amount of time has passed to reduce the - possibility of a user slowing the system by reading this file. - -2. Writing - - Writing to the ppc_htab allows you to change the characteristics of - the powerpc PTE hash table and setup performance monitoring. - - Resizing the PTE hash table is not enabled right now due to many - complications with moving the hash table, rehashing the entries - and many many SMP issues that would have to be dealt with. - - Write options to ppc_htab: - - - To set the size of the hash table to 64Kb: - - echo 'size 64' > /proc/ppc_htab - - The size must be a multiple of 64 and must be greater than or equal to - 64. - - - To turn off performance monitoring: - - echo 'off' > /proc/ppc_htab - - - To reset the counters without changing what they're counting: - - echo 'reset' > /proc/ppc_htab - - Note that counting will continue after the reset if it is enabled. - - - To count only events in user mode or only in kernel mode: - - echo 'user' > /proc/ppc_htab - ...or... - echo 'kernel' > /proc/ppc_htab - - Note that these two options are exclusive of one another and the - lack of either of these options counts user and kernel. - Using 'reset' and 'off' reset these flags. - - - The 604 has 2 performance counters which can each count events from - a specific set of events. These sets are disjoint so it is not - possible to count _any_ combination of 2 events. One event can - be counted by PMC1 and one by PMC2. - - To start counting a particular event use: - - echo 'event' > /proc/ppc_htab - - and choose from these events: - - PMC1 - ---- - 'ic miss' - instruction cache misses - 'dtlb' - data tlb misses (not hash table misses) - - PMC2 - ---- - 'dc miss' - data cache misses - 'itlb' - instruction tlb misses (not hash table misses) - 'load miss time' - cycles to complete a load miss - -3. Bugs - - The PMC1 and PMC2 counters can overflow and give no indication of that - in /proc/ppc_htab. |