From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Drokin, Oleg" Date: Fri, 01 May 2015 18:49:39 +0000 Subject: Re: [HPDD-discuss] [PATCH 2/11] Staging: lustre: fld: Use kzalloc and kfree Message-Id: List-Id: References: <1430495482-933-1-git-send-email-Julia.Lawall@lip6.fr> <1430495482-933-11-git-send-email-Julia.Lawall@lip6.fr> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Julia Lawall Cc: "Simmons, James A." , "devel@driverdev.osuosl.org" , Greg Kroah-Hartman , "kernel-janitors@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "HPDD-discuss@lists.01.org" Hello! On May 1, 2015, at 1:48 PM, Julia Lawall wrote: >>> From: Julia Lawall >>> >>> 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 >> >> 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). This is true. We have OBD_ALLOC that is straight kmalloc and then we have OBD_ALLOC_LARGE that depends on allocation size whenever it's kmalloc or vmalloc. Similarly we have OBD_FREE and OBD_FREE_LARGE (This one could be converted straight into kvfree). I think the patches look fine. Bye, Oleg