Date: Wed, 14 Sep 2011 22:53:25 -0400 From: Arnaud Lacombe <lacombar@gmail.com> To: "K. Macy" <kmacy@freebsd.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: buf_ring(9) API precisions Message-ID: <CACqU3MXQ6tD804fKymeFeKDnHndSXVvHJwepYztB4DsnNmtMiw@mail.gmail.com>
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Hi Kip, I've got a few question about the buf_ring(9) API. 1) what means the 'drbr_' prefix. I can guess the two last letter, 'b' and 'r', for Buffer Ring, but what about 'd' and 'r' ? 2) in `sys/sys/buf_ring.h', you defined 'struct buf_ring' as: struct buf_ring { volatile uint32_t br_prod_head; volatile uint32_t br_prod_tail; int br_prod_size; int br_prod_mask; uint64_t br_drops; uint64_t br_prod_bufs; uint64_t br_prod_bytes; /* * Pad out to next L2 cache line */ uint64_t _pad0[11]; volatile uint32_t br_cons_head; volatile uint32_t br_cons_tail; int br_cons_size; int br_cons_mask; /* * Pad out to next L2 cache line */ uint64_t _pad1[14]; #ifdef DEBUG_BUFRING struct mtx *br_lock; #endif void *br_ring[0]; }; Why are you making an MD guess, the amount of padding to fit the size of a cache line, in MI API ? Strangely enough, you did not make this assumption in, say r205488 (picked randomly). Thanks in advance, - Arnaud
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