From: Atsushi Kumagai <kumagai-atsushi@xxxxxxxxxxxxxxxxx> Subject: [RFC] makedumpfile: Improve reading speed with mmap() Date: Wed, 6 Mar 2013 15:48:04 +0900 > Hello, > > I made the prototype patch to use mmap() on /proc/vmcore for > benchmarking. > > This patch simply replaces read(2) with mmap(2), I think we can see > the pure performance improvement by reducing the number of map/unmap. > > - When /proc/vmcore supports mmap(), readmem() calls read_with_mmap() > to read /proc/vmcore with mmap() instead of read(). > > - Introduce --map-size <Kbyte> option to specify the map size. > This option is necessary to use mmap() in this patch, but just for > benchmarking. I'll remove this option in release version and change > the map size into suitable constant size to get enough performance > improvement. > > - This patch is based on devel branch: > http://makedumpfile.git.sourceforge.net/git/gitweb.cgi?p=makedumpfile/makedumpfile;a=shortlog;h=refs/heads/devel > > Unfortunately, I haven't done test and benchmarking in 2nd kernel yet > because I can't start up newer kernel as 2nd kernel on my machine. > (It seems just my environment issue.) > > At least, this patch works for vmcores saved on local disk, > so it will work in 2nd kernel too. > > If anyone helps to do benchmarking, it's very helpful for me. > And any comments for this patch are welcome. Kumagai-san, I think it necessary to compare this generic one with the idea considering virtual memory mapping, which should affect filtering performance to some degree. http://lists.infradead.org/pipermail/kexec/2013-February/007982.html I guess implementation can relatively be moduler. I'll post a prorotype patch for benchmark later. Thanks. HATAYAMA, Daisuke
