Messages in this thread | | | Date | Tue, 10 Mar 2015 14:28:45 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/4] x86: save user rsp in pt_regs->sp on SYSCALL64 fastpath |
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> * Denys Vlasenko <dvlasenk@redhat.com> wrote: > > > > So there are now +2 instructions (5 instead of 3) in the > > > system_call path, but there are -2 instructions in the SYSRETQ > > > path, > > > > Unfortunately, no. [...] > > So I assumed that it was an equivalent transformation, given that > none of the changelogs spelled out the increase in overhead ...
Also, for future reference, you need to spell out performance costs of fast path patches very clearly - and that wasn't done here.
That's a big no-no, please don't do it again ...
Thanks,
Ingo
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