From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible Date: Mon, 03 May 2010 12:18:00 +0300 Message-ID: <4BDE94C8.9000108@redhat.com> References: <1272818776-7729-1-git-send-email-xiaosuo@gmail.com> <4BDDB6E9.4060703@redhat.com> <201005030915.FCD09385.FFHVOMJtSLOFQO@I-love.SAKURA.ne.jp> <4BDE67DA.4080004@redhat.com> <4BDE7E66.8030509@redhat.com> <4BDE8E24.5050200@redhat.com> <4BDE914C.6080504@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Changli Gao , Tetsuo Handa , akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, adobriyan@gmail.com, mingo@elte.hu, peterz@infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Jiri Slaby Return-path: In-Reply-To: <4BDE914C.6080504@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 05/03/2010 12:03 PM, Jiri Slaby wrote: > > >>> Because vmalloc is used to allocate virtually contiguous memory. v in >>> vmalloc means virtually. >>> >>> >>> >> A kmalloc()ed page is virtually contiguous, satisfying your requirement. >> > But it won't work well for vmalloc_to_{page,pfn} and similar. Modify vmalloc_to_{page,pfn} accordingly. > Some code > may expect vmalloc result to be in the vmalloc area and page-aligned > (both in position and size). > Both would be a bug IMO. vmalloc() follows kmalloc() and malloc() which only guarantee natural alignment. > Not that it won't be possible to inspect the callers, but in my eyes it > would definitely be better to introduce kmalloc_or_vmalloc-alike where > the caller explicitly doesn't care about the resulting position and size. > You're forcing every user to make a choice about what's essentially a micro optimization. If it's really needed to have a vmalloc-in-vmalloc-space, that should be a special function, while the ordinary vmalloc should make the optimization. -- error compiling committee.c: too many arguments to function