From: Gerrit Renker Date: Thu, 4 Sep 2008 05:30:19 +0000 (+0200) Subject: dccp: Reduce noise in output and convert to ktime_t X-Git-Tag: v2.6.28-rc1~717^2~305^2~40 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b8c6bcee1dbc1aadcd67af998e414e73fa166a7d;p=pandora-kernel.git dccp: Reduce noise in output and convert to ktime_t This fixes the problem that dccp_probe output can grow quite large without apparent benefit (many identical data points), creating huge files (up to over one Gigabyte for a few minutes' test run) which are very hard to post-process (in one instance it got so bad that gnuplot ate up all memory plus swap). The cause for the problem is that the kprobe is inserted into dccp_sendmsg(), which can be called in a polling-mode (whenever the TX queue is full due to congestion-control issues, EAGAIN is returned). This creates many very similar data points, i.e. the increase of processing time does not increase the quality/information of the probe output. The fix is to attach the probe to a different function -- write_xmit was chosen since it gets called continually (both via userspace and timer); an input-path function would stop sampling as soon as the other end stops sending feedback. For comparison the output file sizes for the same 20 second test run over a lossy link: * before / without patch: 118 Megabytes * after / with patch: 1.2 Megabytes and there was much less noise in the output. To allow backward compatibility with scripts that people use, the now-unused `size' field in the output has been replaced with the CCID identifier. This also serves for future compatibility - support for CCID2 is work in progress (depends on the still unfinished SRTT/RTTVAR updates). While at it, the update to ktime_t was also performed. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald --- Reading git-diff-tree failed