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authorGravatar Ron Yorston <rmy@pobox.com>2016-03-30 00:42:05 +0200
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2016-03-30 00:44:11 +0200
commit610c4c385b38280c7bde7a48d95ec019cbfe1ab4 (patch)
tree82ad4366ce9e927f64efa89d178c4dd2bfea1435 /miscutils/beep.c
parent9844d7e830a2c55421e27e8828d2067c50f57c23 (diff)
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applet_tables: save space by removing applet name offsets
The array applet_nameofs consumes two bytes per applet. It encodes nofork/noexec flags suid flags the offset of the applet name in the applet_name string Change the applet_table build tool to store the flags in two separate arrays (applet_flags and applet_suid). Replace applet_nameofs[] with a smaller version that only stores a limited number of offsets. This requires changes to the macros APPLET_IS_NOFORK, APPLET_IS_NOEXEC and APPLET_SUID. According to Valgrind the original find_applet_by_name required 353 cycles per call, averaged over all names. Adjusting the number of known offsets allows space to be traded off against execution time: KNOWN_OFFSETS cycles bytes (wrt KNOWN_OFFSETS = 0) 0 9057 - 2 4604 32 4 2407 75 8 1342 98 16 908 130 32 884 194 This patch uses KNOWN_OFFSETS = 8. v2: Remove some dead code from the applet_table tool; Treat the applet in the middle of the table as a special case. v3: Use the middle applet to adjust the start of the linear search as well as the last applet found. v4: Use an augmented linear search in find_applet_by_name. Drop the special treatment of the middle name from get_applet_name: most of the advantage now derives from the last stored value. v5: Don't store index in applet_nameofs, it can be calculated. v6: Tweaks by Denys function old new delta find_applet_by_name 25 125 +100 applet_suid - 92 +92 run_applet_no_and_exit 452 460 +8 run_applet_and_exit 695 697 +2 applet_name_compare 31 - -31 applet_nameofs 734 14 -720 ------------------------------------------------------------------------------ (add/remove: 1/1 grow/shrink: 3/1 up/down: 202/-751) Total: -549 bytes text data bss dec hex filename 925464 906 17160 943530 e65aa busybox_old 924915 906 17160 942981 e6385 busybox_unstripped Signed-off-by: Ron Yorston <rmy@pobox.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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