Fix cobalt_should_drop() and reduce memory reallocations #137
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cobalt_should_drop() tries to set CE via INET_ECN_set_ce() call, but this function falsely relies on skb->protocol to determine network header. Fix this by implementing cobalt_set_ce() helper and employ cake_skb_proto() for proper detection. Fixes: 3fb9914 ("Retire usage of cobalt.c and merge cobalt functionality elsewhere") Fixes: 6cc4172 ("Add COBALT core algorithm - combination of simplfied Codel and BLUE.") Signed-off-by: Ilya Ponetayev <i.ponetaev@ndmsystems.com>
cake_handle_diffserv() tries to linearize mac and network header parts of skb and to make it writable unconditionally. In some cases it leads to full skb reallocation, which reduces throughput and increases CPU load. Some measurements of IPv4 forward + NAPT on MIPS router with 580 MHz single-core CPU was conducted. It appears that on kernel 4.9 skb_try_make_writable() reallocates skb, if skb was allocated in ethernet driver via so-called 'build skb' method from page cache (it was discovered by strange increase of kmalloc-2048 slab at first). Obtain DSCP value via read-only skb_header_pointer() call, and leave linearization only for DSCP bleaching or ECN CE setting. Fixes: 6ff4561 ("sch_cake: Make sure we can write the IP header before changing DSCP bits") Signed-off-by: Ilya Ponetayev <i.ponetaev@ndmsystems.com>
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Merged as 0d67568 (with a few fixups) |
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Open brand new PR for proper history, see #136