Messages in this thread | | | Date | Thu, 18 Jun 2009 14:17:02 -0700 | From | Corey Ashford <> | Subject | Re: [tip:perfcounters/core] perf_counter tools: Handle lost events |
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tip-bot for Peter Zijlstra wrote: > Commit-ID: 9d91a6f7a489eb914c16b82d927f9d81d629c259 > Gitweb: http://git.kernel.org/tip/9d91a6f7a489eb914c16b82d927f9d81d629c259 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > AuthorDate: Thu, 18 Jun 2009 11:40:28 +0200 > Committer: Ingo Molnar <mingo@elte.hu> > CommitDate: Thu, 18 Jun 2009 14:46:11 +0200 > > perf_counter tools: Handle lost events > > Make use of the new ->data_tail mechanism to tell kernel-space > about user-space draining the data stream. Emit lost events > (and display them) if they happen. [snip] > @@ -109,7 +120,7 @@ static void mmap_read(struct mmap_data *md) > * In either case, truncate and restart at head. > */ > diff = head - old; > - if (diff > md->mask / 2 || diff < 0) { > + if (diff < 0) { > struct timeval iv; > unsigned long msecs; > [snip]
Hi Peter,
Very nice change. One thing missing though on the above is an update to the comment which precedes snippet, which currently reads:
/* * If we're further behind than half the buffer, there's a chance * the writer will bite our tail and mess up the samples under us. * * If we somehow ended up ahead of the head, we got messed up. * * In either case, truncate and restart at head. */
The "further behind than half the buffer" no longer pertains. Maybe:
/* * If we've gotten behind, truncate and restart at head. */
Regards,
- Corey
Corey Ashford Software Engineer IBM Linux Technology Center, Linux Toolchain cjashfor@us.ibm.com
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