On 03/21/2012 09:45 PM, Christoph Lameter wrote: > On Wed, 21 Mar 2012, Lai Jiangshan wrote: > >> Yes, I don't want to build a complex kmalloc_align(). But after I found >> that SLAB/SLUB's kmalloc-objects are natural/automatic aligned to >> a proper big power of two. I will do nothing if I introduce kmalloc_align() >> except just care the debugging. > > They are not guaranteed to be aligned to the big power of two! There are > kmalloc caches that are not power of two. Debugging and other > necessary meta data may change alignment in both SLAB and SLUB. SLAB needs > a metadata structure in each page even without debugging that may cause > alignment issues. "Debugging and other necessary meta data" are handled in special way in my patches. (You have already checked the patches.) Normally, as I said, SLAB/SLUB's kmalloc-objects are natural/automatic aligned, and my patch does not touch the general cases. Sorry for my bad reply. > >> And kmalloc_align() can be used in the following case: >> o a type object need to be aligned with cache-line for it contains a frequent >> update-part and a frequent read-part. >> o The total number of these objects in a given type is not much, creating >> a new slab cache for a given type will be overkill. >> >> This is a RFC patch and it seems mm gurus don't like it. I'm sorry I >> bother all of you. > > Ideas are always welcome. Please do not get offended by our problems with > your patch. > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>