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*Performance analysis* ([[!wikipedia Performance_analysis desc="Wikipedia
article"]]) deals with analyzing how computing resources are used for
completing a specified task.

[[Profiling]] is one relevant tool.

In [[microkernel]]-based systems, there is generally a considerable [[RPC]]
overhead.

In a multi-server system, it is non-trivial to implement a high-performance
[[I/O System|community/gsoc/project_ideas/disk_io_performance]].

When providing [[faq/POSIX_compatibility]] (and similar interfaces) in an
environemnt that doesn't natively implement these interfaces, there may be a
severe performance degradation.  For example, in this [[`fork` system
call|/glibc/fork]]'s case.

[[Unit_testing]] can be used for tracking performance regressions.

---

  * [[Degradation]]

  * [[fork]]

  * [[IPC_virtual_copy]]

  * [[microbenchmarks]]

  * [[microkernel_multi-server]]

  * [[gnumach_page_cache_policy]]

  * [[metadata_caching]]

---


# IRC, freenode, #hurd, 2012-07-05

    <braunr> the more i study the code, the more i think a lot of time is
      wasted on cpu, unlike the common belief of the lack of performance being
      only due to I/O


## IRC, freenode, #hurd, 2012-07-23

    <braunr> there are several kinds of scalability issues
    <braunr> iirc, i found some big locks in core libraries like libpager and
      libdiskfs
    <braunr> but anyway we can live with those
    <braunr> in the case i observed, ext2fs, relying on libdiskfs and libpager,
      scans the entire file list to ask for writebacks, as it can't know if the
      pages are dirty or not
    <braunr> the mistake here is moving part of the pageout policy out of the
      kernel
    <braunr> so it would require the kernel to handle periodic synces of the
      page cache
    <antrik> braunr: as for big locks: considering that we don't have any SMP
      so far, does it really matter?...
    <braunr> antrik: yes
    <braunr> we have multithreading
    <braunr> there is no reason to block many threads while if most of them
      could continue
    <braunr> -while
    <antrik> so that's more about latency than throughput?
    <braunr> considering sleeping/waking is expensive, it's also about
      throughput
    <braunr> currently, everything that deals with sleepable locks (both
      gnumach and the hurd) just wake every thread waiting for an event when
      the event occurs (there are a few exceptions, but not many)
    <antrik> ouch


# IRC, freenode, #hurd, 2012-09-13

{{$news/2011-q2#phoronix-3}}.

    <braunr> the phoronix benchmarks don't actually test the operating system
      ..
    <hroi_> braunr: well, at least it tests its ability to run programs for
      those particular tasks
    <braunr> exactly, it tests how programs that don't make much use of the
      operating system run
    <braunr> well yes, we can run programs :)
    <pinotree> those are just cpu-taking tasks
    <hroi_> ok
    <pinotree> if you do a benchmark with also i/o, you can see how it is
      (quite) slower on hurd
    <hroi_> perhaps they should have run 10 of those programs in parallel, that
      would test the kernel multitasking I suppose
    <braunr> not even I/O, simply system calls
    <braunr> no, multitasking is ok on the hurd
    <braunr> and it's very similar to what is done on other systems, which
      hasn't changed much for a long time
    <braunr> (except for multiprocessor)
    <braunr> true OS benchmarks measure system calls
    <hroi_> ok, so Im sensing the view that the actual OS kernel architecture
      dont really make that much difference, good software does
    <braunr> not at all
    <braunr> i'm only saying that the phoronix benchmark results are useless
    <braunr> because they didn't measure the right thing
    <hroi_> ok