Package: dpkg Version: 1.15.5.2 Severity: wishlist Tags: patch
By using posix_fadvise with POSIX_FADV_WILLNEED on /var/dpkg/info/*.list, the time needed to read the database can be reduced in the case where the files are not yet in the buffer cache. The attached patch gives 20-30% time reduction for installing one small package on my system (tested with echo 3 > /proc/sys/vm/drop_caches).
diff -Nru dpkg-1.15.5.2/src/filesdb.c dpkg-1.15.5.2+nmu1/src/filesdb.c --- dpkg-1.15.5.2/src/filesdb.c 2009-11-18 08:28:44.000000000 +0100 +++ dpkg-1.15.5.2+nmu1/src/filesdb.c 2009-11-22 22:23:24.000000000 +0100 @@ -19,6 +19,8 @@ * along with this program. If not, see <http://www.gnu.org/licenses/>. */ +#define _XOPEN_SOURCE 600 + #include <config.h> #include <compat.h> @@ -257,14 +259,28 @@ struct pkgiterator *it; struct pkginfo *pkg; struct progress progress; + int fd; if (allpackagesdone) return; if (saidread<2) { int max = countpackages(); saidread=1; - progress_init(&progress, _("(Reading database ... "), max); + progress_init(&progress, _("(Reading database ... "), 2 * max); + } + + it = iterpkgstart(); + while ((pkg = iterpkgnext(it)) != NULL) { + fd = open(pkgadminfile(pkg,LISTFILE), O_RDONLY|O_NOATIME|O_NONBLOCK|O_NOCTTY); + if (fd != -1) { + posix_fadvise(fd, 0, 0, POSIX_FADV_WILLNEED); + close(fd); + } + + if (saidread == 1) + progress_step(&progress); } + iterpkgend(it); it= iterpkgstart(); while ((pkg = iterpkgnext(it)) != NULL) {
