On Fri, 13 Apr 2007 14:31:52 +0100 David Howells <[EMAIL PROTECTED]> wrote:
> Break the counter down like this: > > 0x00000000 - not locked; queue empty > 0x40000000 - locked by writer; queue empty > 0xc0000000 - locket by writer; queue occupied > 0x0nnnnnnn - n readers; queue empty > 0x8nnnnnnn - n readers; queue occupied If space considerations are that important, we could then reserve one bit for the 'wait_lock spinlock' 0x20000000 : one cpu gained control of 'wait_list' This would save 4 bytes on 32 bit platforms. 64 bit platforms could have a limit of 2^60 threads, instead of the way too small 2^28 one ;) (we loose the debug version of spinlock of course) Another possibility to save space would be to move wait_lock/wait_list outside of rw_semaphore, in a hashed global array. This would save 12/16 bytes per rw_semaphore (inode structs are probably the most demanding) - 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/
