Messages in this thread | | | Subject | Re: [PATCH 2/25] NTFS: Allow highmem kmalloc() in ntfs_malloc_nofs() and add _nofail() version. | From | Anton Altaparmakov <> | Date | Fri, 09 Sep 2005 12:02:20 +0100 |
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On Fri, 2005-09-09 at 13:36 +0300, Pekka Enberg wrote: > On 9/9/05, Anton Altaparmakov <aia21@cam.ac.uk> wrote: > > -static inline void *ntfs_malloc_nofs(unsigned long size) > > +static inline void *__ntfs_malloc(unsigned long size, > > + unsigned int __nocast gfp_mask) > > { > > if (likely(size <= PAGE_SIZE)) { > > BUG_ON(!size); > > /* kmalloc() has per-CPU caches so is faster for now. */ > > - return kmalloc(PAGE_SIZE, GFP_NOFS); > > - /* return (void *)__get_free_page(GFP_NOFS | __GFP_HIGHMEM); */ > > + return kmalloc(PAGE_SIZE, gfp_mask); > > + /* return (void *)__get_free_page(gfp_mask); */ > > } > > if (likely(size >> PAGE_SHIFT < num_physpages)) > > - return __vmalloc(size, GFP_NOFS | __GFP_HIGHMEM, PAGE_KERNEL); > > + return __vmalloc(size, gfp_mask, PAGE_KERNEL); > > Unrelated to this patch but why do you have this wrapper instead of > using kmalloc() where you can and__vmalloc() where you really have to?
Very easy. Allocations are variable sized. Without the wrapper I would have to copy and paste the wrapped code all over the ntfs driver as there is no way to tell which one I would need in advance.
I used to simply use vmalloc() but that caused loads of people's machines to run out of vmalloc space in a matter of hours and also vmalloc is much slower so I added the kmalloc if a page and vmalloc otherwise.
Note just using kmalloc is no good as it doesn't go high enough in size (again this problem was being hit by people which is why I had switched to vmalloc in the first place).
Also kmalloc with size > PAGE_SIZE used to cause machines to run OOM and give page order > 1 allocation failures, hence why I never use kmalloc for more than one page any more.
Also note I only use the ntfs_malloc_nofs() wrapper if I have to. If I know how much I am allocating or at least know that the maximum is quite small, I use kmalloc() directly. It is pretty much only for the runlist allocations that I use the wrapper as the runlist is typically small but for fragmented files it can grow huge. I have seen runlists consuming over 256kiB of ram, without vmalloc that would be a real problem...
Best regards,
Anton -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
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