30d0b36828
On 64bit applications the VDSO is the only thing in segment 0. Since the VDSO is position independent we can remove the hint and let get_unmapped_area pick an area. This will mean the vdso will be near other mmaps and will share an SLB entry: 10000000-10001000 r-xp 00000000 08:06 5778459 /root/context_switch_64 10010000-10011000 r--p 00000000 08:06 5778459 /root/context_switch_64 10011000-10012000 rw-p 00001000 08:06 5778459 /root/context_switch_64 fffa92ae000-fffa92b0000 rw-p 00000000 00:00 0 fffa92b0000-fffa9453000 r-xp 00000000 08:06 4334051 /lib64/power6/libc-2.9.so fffa9453000-fffa9462000 ---p 001a3000 08:06 4334051 /lib64/power6/libc-2.9.so fffa9462000-fffa9466000 r--p 001a2000 08:06 4334051 /lib64/power6/libc-2.9.so fffa9466000-fffa947c000 rw-p 001a6000 08:06 4334051 /lib64/power6/libc-2.9.so fffa947c000-fffa9480000 rw-p 00000000 00:00 0 fffa9480000-fffa94a8000 r-xp 00000000 08:06 4333852 /lib64/ld-2.9.so fffa94b3000-fffa94b4000 rw-p 00000000 00:00 0 fffa94b4000-fffa94b7000 r-xp 00000000 00:00 0 [vdso] <----- here I am fffa94b7000-fffa94b8000 r--p 00027000 08:06 4333852 /lib64/ld-2.9.so fffa94b8000-fffa94bb000 rw-p 00028000 08:06 4333852 /lib64/ld-2.9.so fffa94bb000-fffa94bc000 rw-p 00000000 00:00 0 fffe4c10000-fffe4c25000 rw-p 00000000 00:00 0 [stack] On a microbenchmark that bounces a token between two 64bit processes over pipes and calls gettimeofday each iteration (to access the VDSO), our context switch rate goes from 268k to 277k ctx switches/sec (tested on a 4GHz POWER6). Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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