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Feature #7805

closed

want faster clock_gettime

Added by Patrick Mooney over 5 years ago. Updated over 5 years ago.

Status:
Closed
Priority:
Normal
Category:
kernel
Start date:
2017-01-25
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:
needs-triage
Gerrit CR:

Description

There is a large body of software today which calls clock_gettime() with extremely high frequency. On many operating systems, this functionality is implemented in such a way that it's performed entirely in userspace (via the vDSO on Linux), cutting down on the cost. This is not the case for illumos, which relies on the normal syscall path. On modern x86 hardware, clock_gettime() takes 30-50ns on Linux whereas on illumos, it's closer to 250ns+.

In order for software which heavily relies on frequent clock access, it would be nice to have access to the time via a userspace-only mechanism.
This has been implemented in SmartOS as OS-5192.
Various fixes and updates have been made to it in subsequent tickets.


Related issues

Related to illumos gate - Feature #11275: gettimeofday should use comm pageClosedPatrick Mooney

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Related to illumos gate - Feature #12345: comm page should fallback to syscall after excessive migrationClosedPatrick Mooney

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