Control: tag -1 confirmed On Mon, Dec 21, 2015 at 08:32:33AM +0100, Stefan Fritsch wrote: > Package: apt > Version: 1.1.5 > Severity: normal > > Since some time, the rred phase during aptitude/apt-get update is very > slow and produces very high system cpu-load. > > Today I managed to get an strace of the relevant process (the one > matched by "pgrep -f rred", I don't know the exact name right now). It > does stuff like this: > > 2572 read(3, "P", 1) = 1 > 2572 read(3, "a", 1) = 1 > 2572 read(3, "c", 1) = 1 > 2572 read(3, "k", 1) = 1 > 2572 read(3, "a", 1) = 1 > 2572 read(3, "g", 1) = 1 > 2572 read(3, "e", 1) = 1 > 2572 read(3, ":", 1) = 1 > 2572 read(3, " ", 1) = 1 > 2572 read(3, "o", 1) = 1 > 2572 read(3, "p", 1) = 1 > 2572 read(3, "e", 1) = 1 > 2572 read(3, "n", 1) = 1 > 2572 read(3, "s", 1) = 1 > 2572 read(3, "l", 1) = 1 > 2572 read(3, "i", 1) = 1 > 2572 read(3, "d", 1) = 1 > 2572 read(3, "e", 1) = 1 > 2572 read(3, "-", 1) = 1 > 2572 read(3, "p", 1) = 1 > 2572 read(3, "y", 1) = 1 > 2572 read(3, "t", 1) = 1 > 2572 read(3, "h", 1) = 1 > 2572 read(3, "o", 1) = 1 > 2572 read(3, "n", 1) = 1 > 2572 read(3, "\n", 1) = 1 > 2572 write(4, "Package: openslide-python\n", 26) = 26 > 2572 read(3, "B", 1) = 1 > 2572 read(3, "i", 1) = 1 > 2572 read(3, "n", 1) = 1 > > Maybe buffering is disabled for some file descriptor where it should not > be?
We in fact do not have any buffering in our file layer. gzip, lzma, and bzip2 have some buffering; but for reading raw files, we directly issue read() requests on a raw file descriptor from our Read() method [which we call with size 1]. We could use a FILE* instead of a file descriptor, that would be buffered - or we could add our own generic buffering. (The code could also use some refactoring...) -- Julian Andres Klode - Debian Developer, Ubuntu Member See http://wiki.debian.org/JulianAndresKlode and http://jak-linux.org/. When replying, only quote what is necessary, and write each reply directly below the part(s) it pertains to (`inline'). Thank you.
