Messages in this thread | | | Subject | Re: [PATCH 04/23] vfs: Introduce infrastructure for revoking a file | From | (Eric W. Biederman) | Date | Tue, 02 Jun 2009 15:56:02 -0700 |
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Nick Piggin <npiggin@suse.de> writes:
>> In addition for a complete solution we need: >> - A reliable way the file structures that we need to revoke. >> - To wait for but not tamper with ongoing file creation and cleanup. >> - A guarantee that all with user space controlled duration are removed. >> >> The file_hotplug_lock has a very unique implementation necessitated by >> the need to have no performance impact on existing code. Classic locking > > Well, it isn't no performance impact. Function calls, branches, icache > and dcache...
Practically none.
Everything I could measure was in the noise. It is cheaper than any serializing locking primitive. I ran both lmbench and did some microbenchmark testing. So I know on the fast path the overhead is minimal. Certainly less than what we are doing in sysfs and proc today.
Eric
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