On Tue, Sep 11, 2018 at 11:16:45AM +0300, Alexey Budankov wrote: > > Hi Ingo, > > On 11.09.2018 9:35, Ingo Molnar wrote: > > > > * Alexey Budankov <alexey.budan...@linux.intel.com> wrote: > > > >> It may sound too optimistic but glibc API is expected to be backward > >> compatible > >> and for POSIX AIO API part too. Internal implementation also tends to > >> evolve to > >> better option overtime, more probably basing on modern kernel capabilities > >> mentioned here: http://man7.org/linux/man-pages/man2/io_submit.2.html > > > > I'm not talking about compatibility, and I'm not just talking about glibc, > > perf works under > > other libcs as well - and let me phrase it in another way: basic event > > handling, threading, > > scheduling internals should be a *core competency* of a tracing/profiling > > tool. > > Well, the requirement of independence from some specific libc implementation > as well as *core competency* design approach clarify a lot. Thanks! > > > > > I.e. we might end up using the exact same per event fd thread pool design > > that glibc uses > > currently. Or not. Having that internal and open coded to perf, like Jiri > > has started > > implementing it, allows people to experiment with it. > > My point here is that following some standardized programming models and APIs > (like POSIX) in the tool code, even if the tool itself provides internal open > coded implementation for the APIs, would simplify experimenting with the tool > as well as lower barriers for new comers. Perf project could benefit from > that. > > > > > This isn't some GUI toolkit, this is at the essence of perf, and we are not > > very good on large > > systems right now, and I think the design should be open-coded threading, > > not relying on an > > (perf-)external AIO library to get it right. > > > > The glibc thread pool implementation of POSIX AIO is basically a fall-back > > implementation, for the case where there's no native KAIO interface to rely > > on. > > > >> Well, explicit threading in the tool for AIO, in the simplest case, means > >> incorporating some POSIX API implementation into the tool, avoiding > >> code reuse in the first place. That tends to be error prone and costly. > > > > It's a core competency, we better do it right and not outsource it. > > Yep, makes sense.
on the other hand, we are already trying to tie this up under perf_mmap object, which is what the threaded patchset operates on.. so I'm quite confident that with little effort we could make those 2 things live next to each other and let the user to decide which one to take and compare possibilities would be like: (not sure yet the last one makes sense, but still..) # perf record --threads=... ... # perf record --aio ... # perf record --threads=... --aio ... how about that? I just rebased the thread patchset, will make some tests (it's been few months, so it needs some kicking/checking) and post it out hopefuly this week jirka
