On 14.07.2018 12:52, Maxime Villard wrote: > Le 14/07/2018 à 10:29, Martin Husemann a écrit : >> On Fri, Jul 13, 2018 at 11:49:33PM +0200, Kamil Rytarowski wrote: >>> #ifdefing it out in a non-benchmarking application (I was checking ones >>> that do something with syscalls) is more negligible than 0,3% of >>> overhead in the kernel in a loop. >> >> My vote is on #ifdef by a default-off kernel option as well. >> Next step: optimize the switch, but that is no priority then. Can't we >> use pcu(9) for that? > > I've written this [1], from memory I think it's enough. Kamil, please test > it, because I intend to commit it soon. Same for i386. > > We don't update DR6/DR7 on each return to userland, and rather do it during > context switches, only when one of the two LWPs is using dbregs. When none > is (which always is the case), we don't touch. > > [1] http://m00nbsd.net/garbage/dbregs/amd64.diff There are panic, different to the ones that I observed in the past but still there. [ 118.880204] panic: kernel diagnostic assertion "pcb->pcb_dbregs != NULL" failed: file "/usr/src/sys/arch/x86/x86/dbregs.c", line 13 8 [ 118.880204] cpu0: Begin traceback... [ 118.880204] vpanic() at netbsd:vpanic+0x16f [ 118.880204] ch_voltag_convert_in() at netbsd:ch_voltag_convert_in [ 118.880204] x86_dbregs_store_dr6() at netbsd:x86_dbregs_store_dr6+0x4c [ 118.880204] trap() at netbsd:trap+0x97b I will try to fix the patch and be back to you.
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