add option to force cachestat() usage #3602
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Please update It would be helpful to describe in the man page (e.g., the DESCRIPTION section) that we have the cachestat() and mincore() syscalls and how |
When cachestat() is not available, mmap() and fincore() are used to get cache statistics. This fallback returns less data than cachestat, and potentially hides read errors by reporting that the file is all mapped in memory: $ fincore /usr/bin/java fincore: failed to do cachestat: /usr/bin/java: Operation not permitted RES PAGES SIZE FILE 208K 13 198,1K /usr/bin/java $ echo $? 0 $ sudo fincore /usr/bin/java RES PAGES SIZE FILE 0B 0 198,1K /usr/bin/java Add a --cachestat argument which forces cachestat usage and fails if it's not available: $ fincore -C /usr/bin/java fincore: failed to do cachestat: /usr/bin/java: Operation not permitted $ echo $? 1 Also, on huge files the fallback is very slow and memory consuming, so this flag can be user to avoid doing it by mistake.
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Looks good thanks! |
t-8ch
reviewed
Jun 2, 2025
| switch (c) { | ||
| case 'b': | ||
| ctl.bytes = 1; | ||
| break; | ||
| case 'c': | ||
| ctl.total = 1; | ||
| break; | ||
| case 'C': | ||
| #ifndef HAVE_CACHESTAT |
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This #ifndef can be removed. We have fallback definitions in place.
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and just let the syscall fail in case?
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When cachestat() is not available, mmap() and fincore() are used to get cache statistics.
This fallback returns less data than cachestat, and potentially hides read errors by reporting that the file is all mapped in memory:
Add a --cachestat argument which forces cachestat usage and fails if it's not available:
Also, on huge files the fallback is very slow and memory consuming, so this flag can be user to avoid doing it by mistake.