Re: 2.4 vm, program load, page faulting, ...

[wind-lkml@cocodriloo.com]

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On Mon, Mar 17, 2003 at 06:12:46PM +0100, wind-lkml@cocodriloo.com wrote:
> On Mon, Mar 17, 2003 at 07:50:04PM +0300, Alex Tomas wrote:
> > >>>>> wind  (w) writes:
> > 
> >  w> On Mon, Mar 17, 2003 at 11:01:31AM -0500, Rik van Riel wrote:
> >  >> On Mon, 17 Mar 2003, William Lee Irwin III wrote:
> >  >> > On Sat, 15 Mar 2003, Paul Albrecht wrote:
> >  >> > >> ... Why does the kernel page fault on text pages, present in
> >  >> the page > >> cache, when a program starts? Couldn't the pte's for
> >  >> text present in the > >> page cache be resolved when they're
> >  >> mapped to memory?
> >  >> > 
> > 
> >  w> You should ask Andrew about his patch to do exactly that: he
> >  w> forced all PROC_EXEC mmaps to be nonlinear-mapped and this forced
> >  w> all programs to suck entire binaries into memory...  I recall he
> >  w> saw at least 25% improvement at launching gnome.
> > 
> > they talked about pages _already present_ in pagecache.
> 
> I wonder if this could be done by walking and faulting
> all pages at fs/binfmt_elf.c::elf_map just after do_mmap...
> will try it just now :)

OK, this is not tested, since I'm compiling it now... feel free
to correct :)


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--- orig/fs/binfmt_elf.c	Mon Mar 17 18:26:59 2003
+++ work/fs/binfmt_elf.c	Mon Mar 17 18:26:31 2003
@@ -259,12 +259,23 @@ create_elf_tables(struct linux_binprm *b
 static inline unsigned long
 elf_map (struct file *filep, unsigned long addr, struct elf_phdr *eppnt, int prot, int type)
 {
-	unsigned long map_addr;
+	unsigned long map_addr, pgoff;
+	struct mm *mm;
 
 	down_write(&current->mm->mmap_sem);
 	map_addr = do_mmap(filep, ELF_PAGESTART(addr),
 			   eppnt->p_filesz + ELF_PAGEOFFSET(eppnt->p_vaddr), prot, type,
 			   eppnt->p_offset - ELF_PAGEOFFSET(eppnt->p_vaddr));
+
+	/* preload elf image  */
+
+	mm = current->mm;
+	addr = ELF_PAGESTART(addr);
+	for(pgoff = 0; pgoff < eppnt->p_filesz;){
+		do_mmap_pgoff(mm, filep, addr, PAGE_SIZE, prot, type, pgoff);
+		addr += PAGE_SIZE;
+		pgoff += PAGE_SIZE;
+	}
 
 	up_write(&current->mm->mmap_sem);
 	return(map_addr);