Pekka wrote:
> (4) The cleanups Jesper and others are doing are to remove the
> _redundant_ NULL checks (i.e. it is now checked twice).
Even such obvious changes as removing redundant checks doesn't
seem to ensure a performance improvement. Jesper Juhl posted
performance data for such changes in his microbenchmark a couple
of days ago.
As I posted then, I could swear that his numbers show:
> Just looking at the third run, it seems to me that "if (likely(p))
> kfree(p);" beats a naked "kfree(p);" everytime, whether p is half
> NULL's, or very few NULL's, or almost all NULL's.
Twice now I have asked Jesper to explain this strange result.
I have heard no explanation (not even a terse "you idiot ;)"),
nor anyone else comment on these numbers.
Maybe we should be following your good advice:
> You don't know that until you profile!
instead of continuing to make these code changes.
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.650.933.1373, 1.925.600.0401
-
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/
- Follow-Ups:
- Re: no need to check for NULL before calling kfree() -fs/ext2/
- From: Jesper Juhl <[email protected]>
- Re: no need to check for NULL before calling kfree() -fs/ext2/
- From: "Pekka J Enberg" <[email protected]>
- Re: no need to check for NULL before calling kfree() -fs/ext2/
- References:
- [PATCH] no need to check for NULL before calling kfree() - fs/ext2/
- From: Jesper Juhl <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() - fs/ext2/
- From: Arjan van de Ven <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: linux-os <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Jesper Juhl <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Lee Revell <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Paul Jackson <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Jan Engelhardt <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Dave Jones <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Lee Revell <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Pekka Enberg <[email protected]>
- Re: [PATCH] no need to check for NULL before calling kfree() -fs/ext2/
- From: Jan Engelhardt <[email protected]>
- Re: no need to check for NULL before calling kfree() -fs/ext2/
- From: "Pekka J Enberg" <[email protected]>
- [PATCH] no need to check for NULL before calling kfree() - fs/ext2/
- Prev by Date: Re: i386/x86_64 segment register issuses (Re: PATCH: Fix x86 segment register access)
- Next by Date: Re: Linux 2.4.30-rc3 md/ext3 problems
- Previous by thread: Re: no need to check for NULL before calling kfree() -fs/ext2/
- Next by thread: Re: no need to check for NULL before calling kfree() -fs/ext2/
- Index(es):
 |