------- Additional Comments From sgk at troutmask dot apl dot washington dot edu 2005-05-30 15:15 ------- Subject: Re: Really, really, horrible IO performance
On Mon, May 30, 2005 at 03:00:41PM -0000, pinskia at gcc dot gnu dot org wrote: > > > Note, the use of O_TRUNC on replacing a file should > > not hurt performance on other OS's. > > On powerpc-darwin I am using HFS+. > Hmm, I think I should drag my firewire drive out and try it on the > UFS partition. > A little more investigate shows that this may be a mmap problem. If foo.dat does not exist ktrace ./z kdump -f ktrace.out | grep mmap | wc -l 4 If foo.dat exists, then I see ktrace ./z kdump -f ktrace.out | grep mmap | wc -l 246054 In looking at the ktrace, I see a bunch of segments like 95157 z CALL mmap(0,0x2000,0x3,0x1,0x3,0,0,0) 95157 z RET mmap 1208418304/0x48070000 95157 z CALL munmap(0x48070000,0x2000) 95157 z RET munmap 0 95157 z CALL mmap(0,0x2000,0x3,0x1,0x3,0,0,0) 95157 z RET mmap 1208418304/0x48070000 95157 z CALL munmap(0x48070000,0x2000) 95157 z RET munmap 0 95157 z CALL mmap(0,0x2000,0x3,0x1,0x3,0,0,0) 95157 z RET mmap 1208418304/0x48070000 95157 z Events dropped. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21820