On Mon, Jan 14, 2019 at 11:43:31AM +0300, Alexey Budankov wrote: > Hi, > On 09.01.2019 20:28, Jiri Olsa wrote: > > On Mon, Dec 24, 2018 at 04:21:33PM +0300, Alexey Budankov wrote: > >> > >> The patch set implements runtime record trace compression accompanied by > >> trace file decompression implemented in the tool report mode. Zstandard > >> library API [1] is used for compression/decompression of data that come > >> from perf_events kernel data buffers. > >> > >> Realized -z,--compression_level=n option provides ~3-5x avg. trace file > >> size reduction on the tested workloads what significantly saves user's > >> storage space on larger server systems where trace file size can easily > >> reach several tens or even hundreds of GiBs, especially when profiling > >> with stacks for later dwarf unwinding, context-switches tracing and etc. > >> > >> The option is effective jointly with asynchronous trace writing because > >> compression requires auxiliary memory buffers to operate on and memory > >> buffers for asynchronous trace writing serve that purpose. > > > > I dont like that it's onlt for aio only, I can't really see why it's > > For serial streaming, on CPU bound codes, under full system utilization it > can induce more runtime overhead and increase data loss because amount of > code on performance critical path grows, of course size of written data > reduces but still. Feeding kernel buffer content by user space code to a > syscall is extended with intermediate copying to user space memory with > doing some math on it in the middle. > > > a problem for normal data.. can't we just have one layer before and > > stream the data to the compress function instead of the file (or aio > > buffers).. and that compress functions would spit out 64K size COMPRESSED > > events, which would go to file (or aio buffers) > > It is already almost like that. Compression could be bridged using AIO > buffers but then still streamed to file serially using record__pushfn() > and that would make some sense for moderate profiling cases on systems > without AIO support and trace streaming based on it. > > > > > the report side would process them (decompress) on the session layer > > before the tool callbacks are called > > It is already pretty similar to that.
hum, AFAICS you do that in report code not in on the session layer jirka
