<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Dec 11, 2015 at 4:48 PM, Sean Silva <span dir="ltr"><<a href="mailto:chisophugis@gmail.com" target="_blank">chisophugis@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Wed, Dec 9, 2015 at 12:14 PM, Xinliang David Li via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr">Can you extract the relevant part of the heap profile data? How large is the sample profile data fed to the compiler? <div><br></div><div>The indexed format profile size for clang is <100MB. The InstrProfRecord for each function is read, used and discarded one at a time, so there should not be problem as described.</div></div></blockquote><div><br></div></span><div>If I'm reading the code right, we are also doing O(keys of the hash table) memory allocation in the indexed reader here: <a href="http://llvm.org/docs/doxygen/html/classllvm_1_1InstrProfReaderIndex.html#acc49fd2c0a8c8dfc3e29b01e09869af7" target="_blank">http://llvm.org/docs/doxygen/html/classllvm_1_1InstrProfReaderIndex.html#acc49fd2c0a8c8dfc3e29b01e09869af7</a></div><div>?</div><div>That seems unnecessary. (it seems to be used for value profiling stuff for some reason?)</div></div></div></div></blockquote><div><br></div><div>It is for value profiling -- it is used to convert on-disk callee target value (in md5) to unique string pointer when the function record's VP data is read from memory. I will check its memory overhead at some point. This (the translation) is not strictly needed as a matter of fact (which I actually wanted to get rid of, but did not find time to do yet -- it is on my TODO list).</div><div><br></div><div>David</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class="HOEnZb"><font color="#888888"><div><br></div><div>-- Sean Silva</div></font></span><span class=""><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><br></div><div>David<br><div><br></div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div>On Wed, Dec 9, 2015 at 7:52 AM, Diego Novillo via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div><div><div dir="ltr"><br><div>I've been experimenting with profiled bootstraps using sample profiles. Initially, I made stage2 build stage3 while running under Perf. This produced a 20Gb profile which took too long to convert to LLVM, and used ~30Gb of RAM. So, I decided that this was not going to be very useful for general usage.</div><div><br></div><div>I then changed the bootstrap to instead run each individual compile under Perf. This produced ~2,200 profiles, each of which took up to 1 minute to convert, and then they all have to be merged into a single profile. Also didn't like it.</div><div><br></div><div>Since all compiles are more or less the same in terms of what the compiler does, I decided to take the top 10 biggest profiles and merge those. That seemed to work. This resulted in a 21Mb profile that I could use as input to -fprofile-sample-use.</div><div><br></div><div>I started stage 3 of the bootstrap and left it to work. I noticed it was slow, so I thought "we'll need to speed things up". The build never finished. Instead, ninja crashed my machine.</div><div><br></div><div>It turns out that each clang invocation was growing to 4Gb of RSS. All that memory is being allocated by the profile reader (<a href="https://drive.google.com/file/d/0B9lq1VKvmXKFQVp1cGtZM2RSdWc/view?usp=sharing" target="_blank">https://drive.google.com/file/d/0B9lq1VKvmXKFQVp1cGtZM2RSdWc/view?usp=sharing</a>).</div><div><br></div><div>So, heads up, we need to trim it down. Perhaps by only loading one function profile at a time, use it and actively discard it. Or simply be better at flushing the reader data structures as they're used during annotations. I'll be sending patches about this in the coming days.</div><div><br></div><div>It's likely that the sample reader is doing something silly here. Duncan, Justin, do you have memories of issues like this one with instrumentation? I'll be trying a similar experiment with it after I'm done with the biggest issues in the sampler.</div><div><br></div><div><br></div><div>Thanks. Diego.</div></div>
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