Paul, On Tue, Nov 20, 2007 at 08:43:32AM +1100, Paul Mackerras wrote: > David Miller writes: > > > As a result I've found that perfmon2 is quite nice and allows > > incredibly useful and powerful tools to be written. The syscalls > > aren't that bad and really I see not reason to block it's inclusion. > > > > I rescind all of my earlier objections, let's merge this soon :-) > > Strongly agree. However, I think we need to add structure size > arguments to most of the syscalls so we can extend them later. > Yes, that is one way. It works well if you only extend structures at the end. Given that you need to obtain the file descriptor first via a pfm_create_context call, an alternative could be that you pass a version number to that call to identify the version the application is requesting.
> Also, something I've been meaning to mention to Stephane is that the > use of the cast_ulp() macro in perfmon is bogus and won't work on > 32-bit big-endian platforms such as ppc32 and sparc32. On such I don't like those cast_ulp() macros. They were put there to avoid compiler warnings on some architectures. Clearly with the big-endian issue, we need to find something else. The bitmap*() macros make unsigned long *. The interface uses fixed size type to ensure ABI compatibility between 32 and 64 bit modes. This way there is no need to marhsall syscall arguments for a 32-bit app running on a 64-bit host. Looks like we will have to use bytes (u8) instead. This may have some performance impact as well. Several bitmaps are used in the context/interrupt routines. Even with u8, there is still a problem with the bitmap*() macros. Now, only a small subset of the bitmap() macros are used, so it may be okay to duplicate them for u8. What do you think? > platforms you can't take a pointer to an array of u64, cast it to > unsigned long * and expect the kernel bitmap operations to work > correctly on it. At the least you also need to XOR the bit numbers > with 32 on those platforms. Another alternative is to define the > bitmaps as arrays of bytes instead, which eliminates all byte ordering > and wordsize problems (but makes it more tricky to use the kernel > bitmap functions directly). > -- -Stephane - 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/
