On Thu, 23 Nov 2006 11:57:29 +0100 Eric Dumazet <[EMAIL PROTECTED]> wrote:
> On 32bits SMP platforms, 64bits i_size is protected by a seqcount > (i_size_seqcount). > > When i_size is read or written, i_size_seqcount is read/written as well, so > it > make sense to group these two fields together in the same cache line. > > Before this patch, accessing i_size needed 3 cache lines (2 for i_size, one > for i_size_seqcount). After, only one cache line is needed/ (dirtied on a > i_size change). I didn't understand that paragraph at all, really, so I took it out. At present an i_size change will dirty one, two or three cachelines, most likely one or two. After your patch an i_size change will dirty one or two cachelines, most likely one. yes? > This patch moves i_size_seqcount next to i_size, and also moves i_version to > let offsetof(struct inode, i_size) being 0x40 instead of 0x3c (for 32bits > platforms). > > For 64 bits platforms, i_size_seqcount doesnt exist, and the move of a 'long > i_version' should not introduce a new hole because of padding. > > Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
