On Sun, Apr 10, 2016 at 6:59 PM, Joe Perches <joe@xxxxxxxxxxx> wrote: > On Sun, 2016-04-10 at 18:24 +0200, Denys Vlasenko wrote: >> Fastest existing Bluetooth standard's top speed is 2.4 MB/s. >> It is way off from being CPU limited, no need to squeeze >> last few cycles by excessive inlining. >> >> This patch delinlines the following functions: >> >> hci_conn_hash_lookup_handle: 345 bytes, 39 calls >> hci_conn_hash_lookup_ba: 372 bytes, 36 calls >> hci_conn_hash_lookup_le: 382 bytes, 8 calls >> hci_conn_hash_lookup_state: 356 bytes, 3 calls >> hci_lookup_le_connect: 378 bytes, 7 calls >> hci_conn_drop: 186 bytes, 30 calls >> hci_connect_cfm: 121 bytes, 15 calls >> hci_disconn_cfm: 121 bytes, 2 calls >> hci_auth_cfm: 156 bytes, 2 calls >> hci_encrypt_cfm: 156 bytes, 3 calls >> >> Size reduction is about 40k: >> >> text data bss dec hex filename >> 95943139 20860256 35991552 152794947 91b7743 vmlinux_before >> 95903714 20860256 35991552 152755522 91add42 vmlinux > > Hello Denys > > While removing unnecessary inlines is generally a > good thing, for extremely low power embedded systems > like a coin-battery operated bicycle computer or a > heart rate monitor, this might cause a throughput > reduction. Todays CPUs can push several GB/s over, say, Ethernet. BT is 2.4 MB/s, tops. Therefore total CPU time spent preparing BT I/O must be in the 0.1% ballpark. (Meaning, if we would have a magical infinitely fast CPU, throughput would possibly increase by about 0.1%). How much do you think this deinlining patch can possibly hurt here? > Can you please also show the size decrease when done > with a defconfig with bluetooth support? > > And for these types of patches in general, please > add a defconfig size reduction to the commit message. Okay, will do in the future. > This is an x86-64 defconfig with bluetooth with and > without this patch: > > $ size vmlinux.defconfig.* > text data bss dec hex filename > 10214414 4313816 1097728 15625958 ee6ee6 vmlinux.defconfig.new > 10224014 4313816 1097728 15635558 ee9466 vmlinux.defconfig.old > > ~10k total Looks good, right? -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
