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Message-ID: <20100619221611.784f7dbc@nehalam> Date: Sat, 19 Jun 2010 22:16:11 -0700 From: Stephen Hemminger <shemminger@...tta.com> To: Hagen Paul Pfeifer <hagen@...u.net> Cc: netdev@...r.kernel.org, davem@...emloft.net Subject: Re: [PATCH] net: optimize Berkeley Packet Filter (BPF) processing On Sun, 20 Jun 2010 05:05:36 +0200 Hagen Paul Pfeifer <hagen@...u.net> wrote: > Gcc is currenlty not in the ability to optimize the switch statement in > sk_run_filter() because of dense case labels. This patch replace the > OR'd labels with ordered sequenced case labels. The sk_chk_filter() > function is modified to patch/replace the original OPCODES in a > ordered but equivalent form. gcc is now in the ability to transform the > switch statement in sk_run_filter into a jump table of complexity O(1). > > Until this patch gcc generates a sequence of conditional branches (O(n) of 567 > byte .text segment size (arch x86_64): I don't think this works because it breaks ABI compatibility for applications tha use older versions. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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