Re: [HPDD-discuss] [PATCH 2/11] Staging: lustre: fld: Use kzalloc and kfree

>> >From: Julia Lawall <Julia.Lawall(a)lip6.fr&gt; >> > >> >Replace OBD_ALLOC, OBD_ALLOC_WAIT, OBD_ALLOC_PTR, and OBD_ALLOC_PTR_WAIT by >> >kalloc/kcalloc, and OBD_FREE and OBD_FREE_PTR by kfree. >> >> Nak: James Simmons <jsimmons(a)infradead.org&gt; >> >> A simple replace will not work. The OBD_ALLOC and OBD_FREE functions allocate memory >> anywhere from one page to 4MB in size. You can't use kmalloc for the 4MB allocations. >> Currently lustre uses a 4 page water mark to determine if we allocate using vmalloc. Even >> using kmalloc for 4 pages has shown high failure rates on some systems. It gets even more >> messy with 64K page systems like ppc64 boxes. Now I'm not suggesting to port the larger >> allocations to vmalloc either since issues have been founded with using vmalloc. For example >> when using large stripe count files the MDS rpc generated crosses the 4 page line and vmalloc >> is used. Using vmalloc caused a global spinlock to be taken which causes meta data operations >> to serialized on the MDS servers. > >It's not the LARGE functions that do the switching? For example OBD_ALLOC >ends up at __OBD_MALLOC_VERBOSE, which as far as I can see calls kmalloc >(with __GFP_ZERO, and hance the use of kzalloc). Yes the LARGE functions do the switching. I was expecting also patches to remove the OBD_ALLOC_LARGE functions as well which is not the case here. I do have one question still. The macro __OBD_MALLOC_VERBOSE allowed the ability to simulate memory allocation failures at a certain percentage rate. Does something exist in the kernel to duplicate that functionality?