Hello, I got a mail from Andrew Morton that he fixed my typo and poor English like this: http://ozlabs.org/~akpm/mmots/broken-out/mm-vmallocc-enhance-vm_map_ram-comment-fix.patch Thank you for your attention. > -----Original Message----- > From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel- > owner@xxxxxxxxxxxxxxx] On Behalf Of SeongJae Park > Sent: Tuesday, March 11, 2014 8:51 PM > To: Gioh Kim > Cc: Zhang Yanfei; Minchan Kim; Andrew Morton; Joonsoo Kim; linux- > mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; 이건호; chanho.min@xxxxxxx; > Johannes Weiner > Subject: Re: Subject: [PATCH] mm: use vm_map_ram for only temporal object > > Hello Gioh, > > On Mon, Mar 10, 2014 at 7:16 PM, Gioh Kim <gioh.kim@xxxxxxx> wrote: > > > > The vm_map_ram has fragment problem because it couldn't purge a > > chunk(ie, 4M address space) if there is a pinning object in that > > addresss space. So it could consume all VMALLOC address space easily. > > We can fix the fragmentation problem with using vmap instead of > > vm_map_ram but vmap is known to slow operation compared to vm_map_ram. > > Minchan said vm_map_ram is 5 times faster than vmap in his experiment. > > So I thought we should fix fragment problem of vm_map_ram because our > > proprietary GPU driver has used it heavily. > > > > On second thought, it's not an easy because we should reuse freed > > space for solving the problem and it could make more IPI and bitmap > > operation for searching hole. It could mitigate API's goal which is very > fast mapping. > > And even fragmentation problem wouldn't show in 64 bit machine. > > > > Another option is that the user should separate long-life and > > short-life object and use vmap for long-life but vm_map_ram for short- > life. > > If we inform the user about the characteristic of vm_map_ram the user > > can choose one according to the page lifetime. > > > > Let's add some notice messages to user. > > > > Signed-off-by: Gioh Kim <gioh.kim@xxxxxxx> > > Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> > > --- > > mm/vmalloc.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 0fdf968..85b6687 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1083,6 +1083,12 @@ EXPORT_SYMBOL(vm_unmap_ram); > > * @node: prefer to allocate data structures on this node > > * @prot: memory protection to use. PAGE_KERNEL for regular RAM > > * > > + * If you use this function for below VMAP_MAX_ALLOC pages, it could > > + be faster > > + * than vmap so it's good. But if you mix long-life and short-life > > + object > > + * with vm_map_ram, it could consume lots of address space by > > + fragmentation > > + * (expecially, 32bit machine). You could see failure in the end. > > looks like trivial typo. Shouldn't s/expecially/especially/ ? > > Thanks. > > > + * Please use this function for short-life object. > > + * > > * Returns: a pointer to the address that has been mapped, or %NULL on > failure > > */ > > void *vm_map_ram(struct page **pages, unsigned int count, int node, > > pgprot_t prot) > > -- > > 1.7.9.5 > > > > > > -- > > 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/ . > > Don't email: <a hrefmailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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/ . Don't email: <a href