Date: Thu, 19 Nov 2009 11:15:01 -0500 From: Jung-uk Kim <jkim@FreeBSD.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r199498 - in head/sys: amd64/amd64 i386/i386 net Message-ID: <200911191115.11088.jkim@FreeBSD.org> In-Reply-To: <alpine.BSF.2.00.0911190819550.12162@fledge.watson.org> References: <200911182340.nAINeJ3W087652@svn.freebsd.org> <alpine.BSF.2.00.0911190819550.12162@fledge.watson.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thursday 19 November 2009 03:26 am, Robert Watson wrote: > On Wed, 18 Nov 2009, Jung-uk Kim wrote: > > - Change internal function bpf_jit_compile() to return allocated > > size of the generated binary and remove page size limitation for > > userland. - Use contigmalloc(9)/contigfree(9) instead of > > malloc(9)/free(9) to make sure the generated binary aligns > > properly and make it physically contiguous. > > Is physical contiguity actually required here -- I would have > thought virtual contiguity and alignment would be sufficient, in > which case the normal trick is to allocate using malloc the size + > min-align + 1 and then fudge the pointer forward until it's > properly aligned. I don't believe it is strictly necessary but I assumed it might have performance benefit for very big BPF programs although I have not measured it. Also, contigmalloc(9)/contigfree(9) is too obvious to ignore for this purpose. :-) > Also, in 9.x I'm going to be looking at parallel execution within > BPF descriptors, and I notice that the JIT compiles the register > array pointer into the generated code, rather than allowing a > pointer to be passed in to each instance. I guess it's non-trivial > to change that, suggesting that we have a pool of compiled > instances, but it would be preferable to be able to do what the > normal BPF code does: allocate a per-thread register block when > needed. It is non-trivial but certainly not impossible. Jung-uk Kim
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200911191115.11088.jkim>